Occlusion Dr. Harry Rosen: Dentist and Sculptor/Dentiste et sculpteur

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Occlusion

Dr. Harry Rosen: Dentist and Sculptor/Dentiste et sculpteur

PEER-REVIEWED - JOURNAL - REVUE DES PAIRS

VOLUME 3 - 4Fall/Automne 2010

Canadian Journal ofRestorative Dentistry & Prosthodontics

Publication officielle de l’Académie canadiennede dentisterie restauratrice et de prosthodontie

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MESSAGE FROM THE GUEST CO-EDITOR

Fall 2010 Canadian Journal of Restorative Dentistry & Prosthodontics 3

Where Have All the “Gnathologists” Gone?

We are excited about bringing ourreadership a forum to discuss occlusion

issues as they relate to the practice of dentistryin the 21st century.

Graduating classes are exposed to less and lessocclusion related courses than any generationof dentists before them. Young graduates flockto teaching institutes which teach full mouthrehabilitation over the weekend! A trip to yourlocal dental laboratory confirms that 90% ofthe prosthetics is fabricated on a simple “hingemount” articulator, similar to a nut cracker!

Why is this? What has happened to the study ofocclusion? Why did gnathology become a “fourletter word” in organized/academic dentistry?The Glossary of Prosthodontic Terms definesgnathology as “the science that treats thebiology of the masticatory mechanism as awhole: that is, the morphology, anatomy,histology, physiology, and the therapeutics ofthe jaws or masticatory system and the teeth asthey relate to the health of the whole body,including applicable diagnostic, therapeutic,and rehabilitation procedures.”1

Could there be a higher ideal for a younggraduating dentist or for anyone practicingdentistry for that matter! Major M Ash, Headand Face Medicine 2007:3:1, wrote that theparadigm shift to evidence based dentistry thatrelates to occlusal therapy (OT), selectiveocclusal adjustment (OA), and stabilizationsplint (SS) therapy for TMDs has had anunfavourable impact on the teaching of manyof the important aspects of occlusion neededin daily dental practice.2

The teaching of occlusion has practically beenabandoned in our dental schools because ofEBD induced contraindications for OA and SS.He argues that it is important to bring a clinicalreality back into the dental curriculum bysystematically teaching all aspects of occlusalmanagement. A PubMed search of the topic ofdental occlusion from 1990 to the presentshows little active research being done. This isparticularly evident in North America, as thereis a complete lack of any occlusion relatedresearch emanating from our academicinstitutions.

A recent article in a prominent dental journalprompted me to write this first editorial. Titled,Myths of Orthodontic Gnathology, Dr. DonaldRinchuse wrote, that although originallyfounded on scientific principles, the applicationof the valid gnathologic research to clinicalpractice has moved away from these foundingtenets. He argues that modern clinicalgnathology has become a pseudo-science basedon mechanistic, perfunctory procedures andinstrumentation.3 In so doing, this articlecovers many of the issues that are pertinent tonot just orthodontics but all dentistry! Withoutsufficient research, conflicting treatmentmethodologies and outcomes we struggle withthese questions everyday in clinical practice.

The authors are critical of orthodonticgnatholgy and gnathology in general in theirarticle. It leaves the reader questioning theimportance of many of the basic standards oftreatment that we have become accustomed to!The authors use an extensive list of citations toapply an evidence-based model to theirarguments. This list of references has served hisbiased point of view in several articlespreviously published by the author. I found hisuse of the literature to denounce the work of adeceased colleague rather critical and unfair!

We have published this article in its entirety forour membership to consider. (Please access thefull text in your e-journal!)

I would remind our readers of a quote by WH.McHorris, “We cannot look back and bedamned, nor can we deny the importance ofmandibular centricity; instead let us profit fromthe work of these dental pioneers who have, bythe process of elimination, success, and failure,done so much of our work for us. Let usincorporate those truths that have emergedfrom all the concepts into our diagnostic andtreatment objectives, so we may better serveour patients.”4

My hope is that we will stimulate your interestand be a little controversial and perhapsthought provoking with the possibility, toinitiate a dialogue through our journaleditorials that our members can benefit from.I hope you will enjoy this issue of the journalas much as we have enjoyed preparing it.

On behalf of the editorial board members, bestwishes to all for the Holiday Season!

REFERENCES/RÉFÉRENCES

1. The glossary of prosthodontic terms. J Prosthet Dent 1999;81(1):39–110.

2. Ash MM, Jr. Occlusion, TMDs, and dental education. Head Face Med 2007;3(3):1.

3. Rinchuse D and Kandasamy S. Myths of orthodontic gnathology. Am J Ortho Dentofacial Orthop 2009;136(3):322–330.

4. Mchorris WH. Occlusion with particular emphasis on the functional and parafunctional role of anterior teeth—part 1. J Clin Orthodont 1979;13(9):606–20.

Dr. Kim G. Parlett DDS, MSc.Occlusion Section Co-editorGuest [email protected]

4 Journal canadien de dentisterie restauratrice et de prosthodontie Automne 2010

Nous sommes fiers de pouvoir proposer ànos lecteurs un forum de discussion sur

les questions de l’occlusion comme on laconçoit dans la pratique dentaire au 21e siècle.

Les finissants en art dentaire sont de moins enmoins exposés à des cours sur l’occlusioncomparativement aux générations de dentistesavant eux. Les jeunes diplômés affluent dansles institutions d’enseignement qui offrent descours d’une fin de semaine sur laréhabilitation de la bouche complète. Unepetite visite à votre laboratoire dentaireconfirme que 90 % des prothèses sontfabriquées sur un simple articulateur à « axecharnière » semblable à un casse-noisette.

Pourquoi en est-il ainsi? Qu’est devenuel’étude de l’occlusion? Le Glossaire des termesen prosthodontie définit gnathologie commeétant « la science qui traite la biologie desmécanismes de la mastication : ce qui signifiela morphologie, l’anatomie, l’histologie, laphysiologie et le traitement des mâchoires oudu système de mastication et les dents enrelation avec la santé en général, y compris lediagnostic, le traitement et la réhabilitation »1.

Existe-t-il un idéal plus absolu pour un jeunedentiste ou pour tous ceux qui pratiquent l’artdentaire? Major M. Ash, médecine cranio-faciale 2007 :3 :1 a écrit que le changement deparadigme vers la dentisterie factuelle quiconcerne le traitement de l’occlusion,l’ajustement occlusal sélectif, le traitement aumoyen de gouttière de stabilisation pour letrouble de l’ATM a eu un impact défavorablesur l’enseignement de plusieurs des aspectsimportants de l’occlusion en pratique dentairede tous les jours2.

L’enseignement de la science de l’occlusiondentaire a pratiquement été abandonné parnos facultés dentaires en raison des contre-indications liées au traitement de l’occlusionet l’ajustement occlusal sélectif induites par ladentisterie factuelle. Il fait valoir qu’il estimportant de ramener une réalité clinique auprogramme d’études en enseignantsystématiquement tous les aspects dutraitement occlusal. Une recherche PubMed

sur le sujet de l’occlusion dentaire de 1990 ànos jours démontre bien que peu de rechercheactive est faite dans ce domaine. Cela estparticulièrement évident en Amérique duNord, puisqu’il y a une absence complète derecherche liée à l’occlusion qui est effectuéedans nos facultés.

Un article récent publié dans une revuedentaire éminente m’a incité à rédiger cepremier éditorial. Intitulé Mythes de lagnathologie orthodontique, le Dr DonaldRinchuse a écrit que même si elle est fondéesur des principes scientifiques, l’application dela recherche valide en gnathologie à lapratique clinique s’est éloignée de cesprincipes fondateurs. Il argumente que lagnathologie moderne est devenue unepseudo-science basée sur des procéduresmécanistes, routinières et instrumentales3. Cefaisant, cet article traite non seulement dessujets pertinents à l’orthodontie, mais aussi àtous les domaines de l’art dentaire. Enl’absence de recherche suffisante, noussommes aux prises avec des méthodologiesthérapeutiques et des résultats contradictoireschaque jour en pratique clinique.

Ces auteurs examinent d’un œil critique lagnathologie orthodontique et la gnathologieen général dans leur article. Le lecteur doitalors se questionner sur l’importance desnormes de base thérapeutiques auxquellesnous sommes habitués. Les auteurs utilisentune liste exhaustive de citations pourcorroborer leurs arguments selon un modèlefondé sur les preuves. Les références ont étéutiles à cet auteur pour défendre son point devue biaisé dans plusieurs articles qu’il apubliés. Je trouve que son utilisation de ladocumentation pour dénoncer le travail d’uncollègue décédé plutôt dangereuse et injuste!Nous avons publié cet article au complet pourque nos membres en prennent connaissance.(Veuillez lire le texte en entier dans le e-journal.)

J’aimerais rappeler à nos lecteurs une citationde WH. McHorris : « Nous ne pouvons pasregarder en arrière et s’en ficher, ni nierl’importance de la relation centrée; au lieu de

cela, profitons du travail des pionniersdentaires qui, par processus d’élimination,d’essais et d’erreurs ont accompli tant dechoses pour nous. Incorporons les réalités quiont été révélées de tous les concepts dans nosobjectifs diagnostiques et thérapeutiques pourmieux servir nos patients »4.

J’espère que nous susciterons votre intérêt etvous inspirerons à engager le dialogue parl’intermédiaire de l’éditorial pour que nosmembres puissent en profiter. Je vous souhaiteautant de plaisir à lire ce numéro que nousavons eu à le préparer.Au nom des membres de l’éditorial, je voussouhaite une belle saison des Fêtes!

Dr Kim G. Parlett, DDS, MSc.Co-rédacteur invité – Section occlusion

Où sont passés tous les « gnathologues »

MESSAGE DU CO-RÉDACTEUR INVITÉ

VOL 3, NO.4 • Fall/Automne , 2010

Official Publication of the CanadianAcademy of Restorative Dentistry and Prosthodontics

Publication officielle de L’Académie canadienne de dentisterie restauratrice et de prosthodontie

EDITOR-IN-CHIEF/RÉDACTEUR EN CHEFHubert Gaucher

Québec City, Québec | [email protected]

ASSOCIATE EDITORS/RÉDACTEURS ASSOCIÉSEmmanuel J. Rajczak

Hamilton, Ontario | [email protected] Andrea

Chester, Nova Scotia | [email protected] Nimchuk

Vancouver, British Columbia | [email protected]

SECTION EDITORS/RÉDACTEURS DE SECTIONOcclusion and Temporo-Mandibular Dysfunctions/Occlusion et dysfonctions temporo-mandibulaires

Kim ParlettBracebridge, Ontario | [email protected]

Implant Dentistry/Dentister ie implantaireRon Zokol

Vancouver, British Columbia | [email protected] Fortin

Québec City, Québec | [email protected] Dentistry / Dentister ie esthétique

Paresh ShahWinnipeg, Manitoba | [email protected]

Dental Technology / Technologie dentairePaul Rotsaert

Hamilton, Ontario | [email protected]

MANAGING EDITOR/DIRECTEUR DE LA RÉDACTION

Scott [email protected]

CONTRIBUTORS/CONTRIBUTEURS

ART DIRECTOR/DESIGN /DIRECTEUR ARTISTIQUE/DESIGN

Andrea [email protected]

SALES AND CIRCULATION COORDINATOR/COORDONATRICE DES VENTES ET DE LA DIFFUSION

Brenda [email protected]

TRANSLATION/TRADUCTION

ACCOUNTING / COMPTABILITÉSusan McClung

GROUP PUBLISHER / CHEF DE LA DIRECTIONJohn D. Birkby

[email protected]

CJRDP/JCDRP is published four times annually by Andrew JohnPublishing Inc. with offices at 115 King Street West, Dundas, On, CanadaL9H 1V1. We welcome editorial submissions but cannot assume respon-sibility or commitment for unsolicited material. Any editorial material,including photographs that are accepted from an unsolicited contributor,will become the property of Andrew John Publishing Inc.FeedbackWe welcome your views and comments. Please send them to Andrew JohnPublishing Inc., 115 King Street West, Dundas, On, Canada L9H 1V1.Copyright 2010 by Andrew John Publishing Inc. All rights reserved.Reprinting in part or in whole is forbidden without express written con-sent from the publisher.Individual CopiesIndividual copies may be purchased for a price of $19.95 Canadian. Bulkorders may be purchased at a discounted price with a minimum orderof 25 copies. Please contact Ms. Brenda Robinson at (905) 628-4309 orbrobinson@ andrewjohnpublishing.com for more information and specif-ic pricing.

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Ian TesterSt. Catharines, Ontario | [email protected]

Gladys St. Louis

Samarth Agarwal, Swatantra Agarwal, Atul Bhardwaj, Praveen G, Hubert Gaucher, Saurabh Gupta, Sanjivan Kandesamy, Preeti Kumar,

Sateesh Kumar, Kim Parlett, Michael Racich, Donald Rinchuse, Paul Rotsaert, Ravindra Savadi, Ian Tester, Chris von Rosenbach

Canadian Journal of Restorative Dentistry & Prosthodontics 5

MESSAGE FROM THE GUEST CO-EDITOR

The terms occlusion and temporo-mandibular dysfunction (TMD) elicit

various emotions when discussed by oralhealth care practitioners. All clinicians thatare responsible for direct patient carerecognize the importance of occlusion indental restoration as well as the existence andneed to treat TMD in their patients despitethe controversies.

The predicament is how can we ensure thatwe apply sound scientific principles in ourpatient care with the plethora ofmisinformation and dogma that exists? It isour hope that by providing an opportunityfor open discussion and scientific review inCJRDP we can revisit excellent research thathas been forgotten, as well as offer a forumfor establishing a consensus on how we canutilize the best current research in our day-to-day therapies. Avoidance of these topicsbecause of lack of understanding ofocclusion and TMD can ultimately serve nopurpose. Our goal must be to seek the idealin patient care.

As clinicians, it is important that weunderstand what the term evidence-baseddentistry (EBD) means. The AmericanDental Association (http://ebd.ada.org/about.aspx 2010) defines EBD as “anapproach to oral healthcare that requires thejudicious integration of systematicassessments of clinically relevant scientificevidence, relating to the patient's oral andmedical condition and history, with thedentist's clinical expertise and the patient'streatment needs and preferences”(http://ebd.ada.org). It is clear that toproperly implement EBD in our patient carenecessitates an individualized approach thattakes into account our patient’s desires andvalues, our education and clinicalexperience, and an excellent understandingof the available research.

Perhaps the most difficult conundrum thatwe face is the need to provide EBD that relieson statistically significant results when thenature of occlusal/TMD research is fraughtwith statistical “hazards” in both researchdesign and measurement. The potential ofbias occurs in any investigation due to the

difficulty of double or triple blinding.Confounding factors may influence theresults in an unknown way. For example, astudy of cuspid guidance may determine thatit is appropriate in the population studied.However, it is possible that on closerinvestigation, other factors (e.g., skeletaltype, intercondylar distance, horizontalcondylar inclination, etc.) may have apositive or negative influence. Thedetermination that cuspid guidance isappropriate may in itself be too simplistic.How much guidance is appropriate? Is therea point where too much of good thingactually creates pathology?

EBD aims for the ideal that oral health careprofessionals must use the best evidencecurrently available in their everyday practice.This evidence is available from a variety ofsources ranging from case reports toscientific papers. In the hierarchy ofevidence, reliability is ranked depending onthe type of research completed. Level onereliability of results comes from systematicreview of well designed randomizedcontrolled trials (RCT) and is rankedhighest. While systematic reviews areconsidered the most reliable evidence, theyare still only as reliable as the evidenceassessed. Level two evidence comes from atleast one well designed RCT with anappropriate sample size (n). Trials withoutrandomization that are well designedconstitute level three. Expert opinion andanecdotal findings through case reportsremain at the lower end of the ladder ofevidence (Evidence-Based Nursing Practicehttp://www.ebnp.co.uk 2010). Ideally,experimental design attempts to minimizeboth type I and type II errors, although thisis not always possible. Type I errors (rejectionof the null hypothesis when it is actuallytrue) are affected by the level of significanceof a study. In most studies, there is usuallyless than a 5% chance that the nullhypothesis will be rejected when it is true(significance level less than or equal to .05).Normally, significance levels vary between1% (.01) and 5% (.05). If the null hypothesisis rejected, it is rejected in favour of thealternate hypothesis. Type ll errors are theprobability of retaining the null hypothesis

Occlusion and TM Dysfunction


OCCLUSION AND TM DYSFUNCTION

when it should be rejected because thealternate hypothesis is true. Strategies such asdecreasing the standard deviation of thesampling distributions by decreasing scorevariability (more experimental control) or byincreasing sample size will reveal a minimalmeaningful difference. While these steps willincrease the power of the study (reducing thepossibility that the null hypothesis will beerroneously retained), they are challengingdue to the nature of the humanstomatognathic system. The system isinherently complex and, in our attempt tosimplify it for study purposes, we run a majorrisk of missing the very nature of the system.It exists as a complex inter-relationship ofdifferent parts that are uniquely combined ineach individual and, therefore, must beunderstood by looking at the whole. In orderto provide proper evidence for scientificreview, research design must pay particularattention to selecting the most homogeneousvariables possible to allow clinically usefulconclusions to be drawn. It is necessary forall oral health practitioners to recognize thatin a structure as complex as the

stomatognathic system, it is impossible todefine a cause and effect between altering onevariable and the resulting effect. Anyprocedure that alters even one variable in thesystem will subsequently influence manyother structures.

The inherent paradox that unfolds as westudy the difficulties in researching occlusionand TMD present practicing clinicians witha challenge. How do we best treat the personthat is seeking our expertise? Perhaps theanswer lies in understanding that each of ourpatients is an individual who must beassessed in a very comprehensive way. EBDdictates that we must combine our clinicaljudgement based on our experience, thepatient’s values and desires, and the availablescientific research. Research, therefore, mustconcentrate on developing the means ofidentifying and better assessing all of thefactors that are important to our patient’spresenting situation. We, as clinicians, mustperfect our skill at compiling the myriad ofinformation that we obtain to produce aproper diagnosis and appropriate treatment

plan. The ultimate goal must be to improvefunction. Finally, we should not ignore thepast. A review of the history of occlusion andTMD is necessary to ensure that usefulinformation from past research is not lost. Inaddition, an understanding of where we havebeen can help shape future research protocolsto provide the answers that we must have totreat our patients effectively in an evidence-based manner.

Guest Co-editor – Ian W. Tester DDS, [email protected]

MESSAGE DU CO-RÉDACTEUR INVITÉ

Occlusion et trouble de l’ATM

Les termes « occlusion » et « trouble del’articulation temporomandibulaire

(ATM) » évoquent certaines émotions lors dediscussions avec les cliniciens en santédentaire. Tous les cliniciens qui sontresponsables des soins des patientsreconnaissent l’importance de l’occlusion enrestauration dentaire ainsi que l’existence etle besoin de traiter le trouble de l’ATMmalgré les controverses.

La situation difficile est la suivante :Comment assurer que nous mettons en application d’excellents principesscientifiques pour nos patients compte tenude l’abondance de renseignements erronés et

dogmatiques? Nous espérons qu’en donnantla chance de discuter ouvertement et derevoir les documents scientifiques dans leJCDRP, nous pourrons réexaminerl’excellente recherche qui a été oubliée etoffrir un forum pour parvenir à un consensussur la façon d’utiliser la meilleure rechercheactuelle dans nos traitements quotidiens. Lesoin mis à ne pas aborder ces sujets parmanque de compréhension de l’occlusion etdu trouble de l’ATM ne sert à rien. Notre butdoit être de rechercher l’idéal en ce quiconcerne les soins du patient.

En tant que cliniciens, il est important decomprendre ce que signifie le terme

dentisterie factuelle ou fondée sur despreuves. L’American Dental Association(http://ebd.ada.org/about.aspx 2010) définitla dentisterie factuelle comme suit : « uneapproche aux soins dentaires qui requiertl’intégration judicieuse d’évaluationssystématiques de preuves scientifiquespertinentes du point de vue clinique, enrelation avec l’état de santé générale etbuccale et les antécédents du patient et entenant compte de l’expérience clinique dudentiste et des besoins thérapeutiques et despréférences du patient » (http//ebd.ada.org).Il est évident que pour bien mettre enapplication la dentisterie factuelle il faut uneapproche individualisée qui tient compte des

TESTER


désirs et des valeurs de nos patients, de notreformation, de notre expérience clinique etd’une excellente compréhension de larecherche disponible.

Le problème particulièrement épineuxauquel nous devons faire face est sans doutela nécessité de mettre à la disposition unedentisterie factuelle qui mise sur des résultatsstatistiquement significatifs lorsque la naturede la recherche sur l’occlusion ou le troublede l’ATM recèle de

« risques » statistiques dans le modèle etl’évaluation de recherche. Le potentiel debiais se produit dans toute recherche enraison de la difficulté des études à double età triple insu. Les variables confusionnellespeuvent influencer les résultats de manièreinconnue. Par exemple, une étude sur laguidance canine peut déterminer si cela estapproprié dans la population étudiée.Toutefois, il est possible que lors de l’examenplus approfondi, d’autres facteurs (p. ex. typesquelettique, distance intercondylienne,inclinaison horizontale du condyle, etc.)peuvent avoir une influence positive ounégative. La détermination que la guidancecanine est appropriée peut être en elle-mêmetrop simpliste. Quelle guidance estappropriée? Y a-t-il un point où trop d’unebonne chose crée une pathologie?

La dentisterie factuelle vise l’idéal que lesprofessionnels de la santé dentaire doiventutiliser les meilleures preuves actuellesdisponibles dans leur pratique de tous lesjours. Ces preuves sont disponibles d’unevariété de sources variant de rapports de casà des publications scientifiques. Dans lahiérarchie des données probantes, la fiabilitéest classée selon le type de rechercheterminée. La fiabilité des résultats de niveau1 est établie de l’examen systématiqued’études contrôlées, à répartition aléatoire,bien conçues et est classée comme étant leplus haut niveau. Bien que les examenssystématiques soient considérés comme étantles preuves les plus fiables, leur fiabilité estfonction de l’évaluation des preuves. Lespreuves de niveau 2 proviennent d’au moinsune étude contrôlée, à répartition aléatoire,bien conçue dont la taille de l’échantillon (n)est appropriée. Les études sans répartitionaléatoire qui sont bien conçues constituent le

niveau 3. Les rapports d’experts et lesrapports non scientifiques demeurent au basde l’échelle des preuves (Evidence-BasedNursing Practice http://www.ebnp.co.uk2010). Idéalement, le concept expérimentaltente de minimiser à la fois les erreurs de typeI et de type II, ce qui n’est pas toujourspossible. Les erreurs de type I (rejet del’hypothèse nulle lorsque c’est réellementvrai) sont marquées par le niveau designification d’une étude. Dans la plupart desétudes, il existe habituellement moins de 5 %de chance que l’hypothèse nulle soit rejetéelorsqu’elle est vraie (niveau de significationinférieure ou égale à 0,05). Normalement, lesniveaux de signification varient entre 1 %(0,01) et 5 % (0,05). Si l’hypothèse nulle estrejetée, elle est rejetée en faveur del’hypothèse alternative. Les erreurs de type IIsont les erreurs commises lorsqu’on décidede ne pas rejeter l'hypothèse nulle, alors quecette hypothèse nulle n'est pas vraie. Lesstratégies telles que la diminution de l’écarttype de la distribution d’échantillonnage enréduisant la variabilité du score (plus decontrôle expérimental) ou en augmentant lataille de l’échantillon donneront unedifférence significative minimale. Bien queces étapes augmentent la puissance de l’étude(diminuant la possibilité que l’hypothèsenulle soit retenue par erreur), elles posent demultiples problèmes en raison de la naturedu système stomatognatique. Le système estintrinsèquement complexe et, si nousessayons de le simplifier pour les besoins del’étude, nous courons le risque de passer àcôté de la vraie nature du système. Il existesous forme d’interdépendance complexe departies différentes qui sont combinées demanière unique chez chaque individu et, parconséquent, doivent être comprises enexaminant l’ensemble. Dans le but de fournirdes preuves adéquates pour l’examenscientifique, le plan de la recherche doits’attarder à choisir les variables les plushomogènes afin de pouvoir tirer lesconclusions les plus utiles sur le planclinique. Il est nécessaire pour tous lescliniciens dentaires de reconnaître que dansune structure aussi complexe que le systèmestomatognatique, il est impossible de définirune cause et un effet entre la modificationd’une variable et l’effet du résultat. Touteprocédure qui modifie une variable dans lesystème peut avoir un effet sur plusieurs

autres structures.

Le paradoxe inhérent qui se produit au fur età mesure que nous étudions les difficultés dela recherche sur l’occlusion et le trouble del’ATM représente un enjeu pour lescliniciens. Comment traitons-nous lapersonne qui fait appel à notre savoir-faire?Peut-être que la réponse réside dans lacompréhension que chaque patient doit êtreévalué de manière individuelle et trèsdétaillée. La dentisterie factuelle dicte quenous devons allier notre jugement cliniqueselon notre expérience, les valeurs et désirsdes patients et la recherche scientifiquedisponible. Par conséquent, la recherche doitse concentrer sur le développement demoyens d’identifier et de mieux évaluer tousles facteurs qui sont importants au cas denotre patient. Nous, en tant que cliniciens,devons perfectionner notre aptitude àcompiler une myriade de renseignementsque nous obtenons pour poser le bondiagnostic et établir le bon plan detraitement. Le but ultime doit êtred’améliorer la fonction. Finalement, nous nedevons pas ignorer le passé. Une revue del’historique de l’occlusion et du trouble del’ATM est nécessaire pour faire en sorte quel’information utile de la recherche antérieurene soit pas perdue. De plus, unecompréhension de ce qui a été faitantérieurement aidera à déterminer ce queseront les protocoles de recherche futurs afinde trouver les réponses que nous devonsconnaître pour traiter nos patientsefficacement selon une manière fondée surles preuves.

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CJRDP Editorial Board/Le comité de rédaction JCDRP

Editor-in-Chief/Rédacteur en chefHUBERT GAUCHERQuébec City, Québec

Associate Editors/Rédacteurs associés

Section Editors/Section éditeurs

Occlusion andTemporo-MandibularDysfunctions/Occlusion et Dysfonctionstemporo-mandibulaireKIM PARLETTBracebridge, Ontario

Implant Dentistry/Dentisterie implantaireRON ZOKOLVancouver, British Columbia

Implant Dentistry/Dentisterie implantaireYVAN FORTINQuébec City, Québec

Esthetic Dentistry /Dentisterie esthétiquePARESH SHAHWinnipeg, Manitoba

Dental Technology /Technologie dentairePAUL ROTSAERTHamilton, Ontario

VOLUME 3 • I S SU E 4

Content/Sommaire

FEATUR ES/A RTICLES

3 Message from the Guest Co-editorMessage du co-rédacteur invitéMessage from the Guest Co-editorMessage du co-rédacteur invité

45

16

26

INDICATES PEER REVIEWED/INDIQUE REVUE DES PAIRS

EMMANUELJ. RAJCZAKHamilton,Ontario

MAUREENANDREAChester,

Nova Scotia

DENNISNIMCHUKVancouver,

BritishColumbia

Myths of Orthodontic GnathologyMythes de la gnathologie orthodontiqueBy Dr. Donald J. Rinchuse and Dr. Sanjivan Kandasamy

Occlusal Function and the Single CrownFonction occlusale et couronneBy Mr. Paul Rotsaert RDT

IAN TESTERSt. Catherines, Ontario

Occlusion andTemporo-MandibularDysfunctions/Occlusion et Dysfonctionstemporo-mandibulaire

Occlusion

46 A Brief History of Occlusion in the 19th and 20th CenturiesUne brève histoire de l’occlusion aux 19e et 20e sièclesBy Dr. Ian W. Tester DDS, MSc

38 Anterior Guidance: What Does It Mean To You?Guidance antérieure : Qu’est-ce que cela signi#e pour vous?By Dr. Kim Parlett, DDS, MSc

32 Dental Occlusion Evaluation: 10 Essential StepsÉvaluation de l’occlusion : 10 étapes essentiellesBy Dr. Michael Racich, DMD

53 Simpli#ed Muscle Reconditioning Splint Construction: Rationale, Fabrication, and Case ReportRéalisation simpli#ée de plaques occlusales pour le reconditionnement de la musculature : principe, fabrication et rapport de casBy Dr. Preeti Satheesh Kumar, BDS, MDS; Dr. Satheesh Kumar,BDS,MDS; Dr. Ravindra Savadi, BDS, MDS

59 A Simpli#ed Impression Procedure for A Patient with MicrostomiaUne empreinte simpli#ée pour un patient avec microstomieBy Dr. Praveen G., MDS; Dr. Swatantra Agarwal, MDS; Samarth Agarwal, MDS; Saurabh Gupta, MDSc; Atul Bhardwaj, post-graduate student.

Clinical Forum / Forum cl inique

Cover image of Dr. Harry Rosen and his sculpture "Little Hercules."Photo couverture du Dr Harry Rosen et « Petit Hercule »www.drharryrosen.com.

11 2010 Annual Scienti#c Meeting of the Canadian Academy of Restorative Dentistry and Prosthodontics: October 14-16, Calgary, AlbertaBy Dr. Chris von Rosenbach

62 iPad in BusinessBy Jonathan L. Ferencz, D.D.S., NYC Prosthodontics

Industry News

Academy News / Nouvel les de L 'académie

10 Dentist and Sculptor: Dr. Harry Rosen, Founding and Life MemberDentiste et sculpteur : Dr Harry Rosen, membre fondateur et membre à vie

13

Journal News / Nouvel les du journale-Publishing: Is the Writing Still On the Wall?By Dr. Hubert Gaucher


The academy proudly features Dr. Harry Rosen’s realisations as apractitioner, educator, and artist by quoting his own words when

relating art to dentistry: “In dentistry, first you deal with the task at handby solving your patient’s problem. Then it takes a certain amount ofcreativity and restructuring, working with the elements that you arepresented with, and in many instances, seemingly creating something outof nothing.”

The image above of “The Ascent” was recently inaugurated at theMontreal Jewish General Hospital. Depicting a man climbing a stonewall, it was inspired from the poet Robert Browning’s phrase: “A man’sreach should exceed his grasp or what’s heaven for.” Another notablesculpture by Dr. Rosen, “Little Hercules,” (seen on the cover of this

issue of CJRDP) was inaugurated at the Montreal Children Hospitallast year. Its commemorative plaque reads: “I will be strong/Que la forcesoit avec moi” and is also truly inspirational. To view the making ofthese artworks and Dr. Rosen’s dentist/artist lifelong achievements andcontributions to the dental profession and his community, please visitwww.drharryrosen.com.

Dr. Rosen is an active Professor Emeritus at the Faculty of Dentistry, McGill University, and also maintains a Restorative/Prosthodontic practice in Montréal, Québec. He can be reached at:[email protected].

Dentist and Sculptor: Dr. Harry Rosen, Founding and Life Member

Dentiste et sculpteur : Dr Harry Rosen, membre fondateur et membre à vie

L’Académie est fière de présenter les réalisations du Dr Rosen, dentiste, éducateur et artiste, et de citer ses paroles

lorsqu’il compare la dentisterie à un art : « En dentisterie, vous avezd’abord la tâche de résoudre le problème du patient. Puis il faut unecertaine créativité pour restructurer et travailler avec les éléments enmain et, dans certains cas, créer quelque chose à partir de rien. »

L’œuvre intitulé « The Ascent » a été inauguré tout récemment àl’Hôpital général juif – Sir Mortimer B. Davis à Montréal. Illustrant unhomme escaladant un mur de pierre, il a été inspiré par une phrase dupoète Robert Browning : « Il faut vouloir saisir plus qu’on ne peutétreindre, sinon pourquoi le ciel? » Une autre sculpture remarquable

par le Dr Rosen, « Petit Hercule » (photo couverture de ce numéro) aété inaugurée à l’Hôpital de Montréal pour enfants l’an passé. Sur laplaque commémorative, on peut y lire ce qui suit : « Que la force soitavec moi ». Vous pouvez consulter le site www.drharryrosen pour ensavoir davantage sur les œuvres et les réalisations du Dr Rosen en tantqu’artiste et dentiste, de même que ses contributions à la médecinedentaire et à la collectivité.

Dr Rosen est un Professeur Émérite actif à la Faculté de Médecinedentaire de l’Université McGill, et maintien une pratique de Dentisterie restauratrice et de Prosthodontie à Montréal, Qué[email protected].

ACADEMY NEWS / NOUVELLES DE L'ACADÉMIE

“The Ascent”

ACADEMY NEWS/ NOUVELLES DE L’ACADÉMIE


The dynamic city of Calgary, Albertaprovided the perfect locale for this year’s

annual scientific meeting. With the RockyMountains providing a dramatic backdrop, theCalgary Westin Hotel, just steps from the BowRiver, was the perfect venue to host ouractivities. Convention Chair Ed McIntyre andhis committee saw to it that those lucky enough

to arrive early had the option of goinghorseback riding in the foothills or having a flyfishing experience on the Bow River. The verysatisfied fishing enthusiasts reported anexcellent day trying to snag the wily denizens ofthat beautiful Western river. CARDP anglers,having gone after sturgeon at the Vancouvermeeting and trout in Calgary, can now look

forward to chasing down Lake Ontario salmonat the 2011 meeting in Toronto.

For the more serious-minded, the alwayspopular pre-meeting hands-on course featuredceramist and photographer, Naoki Aiba, CDTfrom Monterey, California. Participants workedthrough the essentials of dentist-lab

2010 Annual Scientific Meeting of the Canadian Academy of Restorative Dentistry and Prosthodontics:

October 14-16, Calgary, AlbertaBy Dr. Chris von Rosenbach

Ophelia (Alfie) Spyker with the country dance band. Left to Right, Dr. Rod Toms, Gerry Leewing, Dr. Carolyn Poonwoo, and Dr. Chris von Rosenbach.

Left to Right: Dr. Rick Freeman, Candace Freeman, Cathrine Robertson, and Dr. Dave Robertson.

Brigitte McIntrye and Conference Chair Dr. Ed McIntyre.


CALGARY 2010

collaboration, facilitated through the mediumof digital photography. For those frustratedwith shade mismatching, canted mid-lines,and visually unpleasing incisal edge lines, therewere plenty of detailed techniques to helpovercome these challenges.

The traditional Opening Reception and Buffet,which allows CARDP members and theirguests to mingle and renew “auldacquaintance,” was held in the foyer justoutside the sponsor area. Our thanks here goto Dennis Nimchuk and his committee, foronce again attracting strong sponsorshipinterest to our annual meeting.

In a departure from CARDP’s traditionalformat, the Friday scientific session was a full-day program featuring just one speaker, theinternationally renowned Dr. David Garberfrom Atlanta, Georgia. Dr. Garber’spresentation had something for everyone. Themorning program concentrated on principlesof crown preparation, dealing with veneers,bonding, and aesthetic temporizationtechniques among other subjects of value toall participants. This was particularlyappreciated by the younger dentists and dentalstudents in the audience. These future CARDPmembers had an inspirational tour of manytechniques, founded on solid principles, toenhance their daily practice lives. (Oneparticular pearl: use a laser to simplify removalof veneers.) The afternoon session providedstimulating information for the moreexperienced dentists in the audience with afocus on implants, solving difficult aestheticdilemmas, and treatment planning forcomplex cases. One highlight was the use ofpink composite to reline pink porcelain, toallow for a very aesthetic solution to theproblem of inadequate soft tissue volume.

The intellectual intensity of the day was thenfollowed in short order by a wild and woollyWestern Night at the Wainwright Hotel on thegrounds of the famous Calgary Heritage Park.

A delicious dinner featuring delectable Albertabeef was followed by line dancing and plentyof good ol’ country music, featuring a very“colourful” band (both sartorially as well asmusically). The guests from all across Canadaleft with a wonderful impression of “WildRose Country” hospitality.

Under the very capable guidance of ScientificProgram Chair Bernard Linke the Saturdayprogram featured four excellent speakers. Thelead-off speaker, Dr. Kevin Lung, is an oral andmaxillofacial surgeon practicing in Edmonton.Dealing with implant issues that most of uswould have nightmares about, his presentationfocussed on understanding good implantsurgery principles, avoiding and dealing withbad outcomes and complications, and thetruly ugly situations which he sometimes hasto deal with. A video showing an accidentsuffered during a non-sanctioned extremesnowmobiling event which resulted intremendous orofacial damage to a patient, wasparticularly disturbing. The excellenttreatment outcome was a memorabletestimony to the restorative powers availablewith good implant technique!

Dr. Glen H. Johnston, who has presented tothe academy before, comes to us from theUniversity of Washington. His subject wasadhesive dentistry and dealt with this criticalpart of every dental practice. He emphasizedin particular that the newer generations ofsingle-bottle adhesives often don’t perform aswell as some of the earlier-generation two-bottle systems. Dr. Johnston recommended acouple of websites which are very useful incomparing dental materials; the ADAprofessional product review website; theAmerican Air Force Medicine website; and theUniversity of Washington website were listedas excellent resources.

Dr. Robert Miller, another past presenter,returned to lecture on the subject of dentallasers. This modality is becoming much more

widely accepted by the dental community andis of particular usefulness with implants. Thehealing time from many surgical procedurescan be cut virtually in half with a laser, ascompared to conventional techniques. Dr. Miller examined factors important in thebiology of healing and illustrated how theproperties of the laser can be used to enhancethe tissue healing process.

Mr. Naoki Aiba, CDT, closed out the morningwith a condensed version of his hands-onprogram. The digital camera is anindispensible tool in the delivery of aestheticdentistry to today’s demanding consumer. Mr.Aiba’s artistry in porcelain and digitalphotography were very much enjoyed by theappreciative audience.

A key feature that differentiates the CARDPmeeting from other dental meetings, is thehalf-day session dedicated to table clinics.Douglas Lobb organized a stellar line-up ofclinicians. CARDP members (who recognizethe value of interactive learning in an intimatesetting) were very complimentary of theexceptional quality of the this year’s tableclinics. In fact, the only complaint was thatthere was not enough time to take in all of thepresentations offered!

As always, the social highlight for attendeesand their guests was the President’s GalaDinner Dance, and this year’s event was noexception. Outgoing president Vern Shaffnergave eloquent thanks for the help he receivedduring his tenure. Incoming president KimParlett thanked Vern for all his hard work andwelcomed everyone to next year’s meeting,September 22 to 24 at the Royal York Hotel inToronto. The diehards (you know who youare) danced all night and wrapped up theevening boogying to the beloved “Time Warp”from The Rocky Horror Picture Show. Whatmore could anyone ask for?


JOURNAL NEWS/ NOUVELLES DU JOURNAL

Nowadays, all dental journals are expected topresent article submissions electronicallythereby allowing for cost-effective peerreviews, expedient modifications, andoptimal printer layouts. In other words, ascientific publication’s paper version is nowbased wholly on its digital version, bringinginto sharp focus the paper version’sshortcomings, namely limited author-readerinteractivity, the absence of linked references,be they scripted, audio or video, and, notleast, a restrictive content and circumscribeddistribution associated with hefty printingcosts.

We have all experienced, over the years,parting pangs when doing away with ourhardcopy professional journals, due to botha lack of storage space and of the timerequired to manage a paper world.Consequently, our academy has moved tooffer a condensed paper format CJRDP infavour of a more elaborate e-version for eachissue dating back to last spring. A recentsurvey of past contributors foundoverwhelming support for this initiativeindicating that these authors are receptive tothe flexibility and interactivity that e-publishing affords.

A seamless transition to these two newjournal concepts is foremost among youreditorial board’s priorities. We each have ourown comfort zone with digital publicationsso an adaptation period is to be expected.After all, for the past 450 years, humans havegotten quite comfortable reading printedpaper in handy, tactile, pliable, and linearconfigurations. And since we are experiencingthe embryonic stages of e-publications, theirfull capabilities and usages are still very muchunknown. We have yet to grasp the potentialintegrated networking forces of digitalcommunications on the web.1

“Bibliophiles are branching out as devicesbecome more book-like” is the lead captionon a recent cover story featuring “A buddinginterest in e-readers.”2 In this article, whatwith so many e-books already outsellinghardcovers, at nearly half the cost, we are toldto expect that by 2013, 50% of all book saleswill be in e-presentation. “We are adapting tothe notion that we can choose where, whenand how we read books” as an estimated 4million US homes own an e-book reader andsales projections of 29 million devices areanticipated for 2015.

You might therefore be tempted to compareand choose an e-book device from therandomly listed manufacturers, reviews andprices, from this same source2:

• Amazon’s Kindle 3G and Wi-Fi ($189US); “Most comfortable to hold because of its light weight”

• Barnes & Noble’s Nook 3G + Wi-Fi ($199US); “The colour touch screen fornavigation is fun and easy to use”

• Sony Reader Pocket Edition ($179–$299US); “Smallest, most elegant-looking device tested; can slip into the pocket of your jeans”

• Libre by Aluratek ($99US); “Biggest wow factor is the price; shortest lag timefor page-turns”

• Apple iPad ($499–$629); Super-cool: You can emulate a paper book by displaying left and right pages at the same time”

Thanks to hyperlinks, e-publishing caninstantaneously allow you to access an

incalculable number of sources andreferences. You could lose yourself surfing thedental literature within just a few clicks.

Add voice/reading software to these e-booksand you could be listening to your recent e-CJRDP while driving to the office or onyour morning jog.

References

1. Greenstein D. Next-Generation University Publishing: A Perspective from California. Journal of Electronic Publishing 2010;13(2). Available at: http://quod.lib.umich.edu/cgi/t/text/text-idx?c=jep;view=text;rgn=main;idno=3336451.0013.205.

2 Minzesheimer B. A budding interest in e-readers, 1-2D, USA Today, October 20,2010.

Dr. Hubert [email protected]

e-Publishing: Is the Writing Still On the Wall?


The paper version of the Canadian Journal ofRestorative Dentistry and Prosthodonticspublishes papers, which are subject to peerreview. The Journal is primarily electronic withfull articles available online; in addition, a printversion of the abstracts from each article is alsosent to all members of CARDP, subscribers tothe print version, dental institutions, andassociations. The Journal considers articles oforiginal research, reviews, scholarly addresses,literature reviews, case reports, book reviews,historical interest, clinical tips, guidelines, lettersto the editor, and so on. Requirements are inaccordance with “Uniform requirements formanuscripts submitted to biomedical journals”(http://www.icmje.org). The editorial policies ofthe journal are in line with those of the Councilof Science Editors (http://www.councilscienceeditors.org/services/draft_approved.cfm). TheJournal endorses the CONSORT statement(www.consort-statement.org) relating toguidelines for improving the Evidence Basedquality reporting of Randomized Clinical Trials(RCTs).

Authors must disclose any commercial interestin the subject of study and the source of anysupport. A covering letter should state that thework is original and should include the addressfor correspondence, as well as the phone and faxnumbers and e-mail address to ensure rapidprocessing. Authors should identify theiraffiliation with a hospital or universitydepartment, and indicate if they are students ordentists. After acceptance of the manuscript, theauthor(s) must sign a copyright transferagreement.

The electronic version of the Canadian Journalof Restorative Dentistry and Prosthodontics willcontain all of the high-quality clinical researchand review articles and editorial material of thepaper version plus additional industry-drivenelements such as product profiles andannouncements. This electronic version ofCJRDP will be published in conjunction withthe paper version of the journal and will be

widely distributed to all CARDP members aswell as over 5,000 other dental professionalsacross the country.

The Journal reserves the right to editmanuscripts to ensure conformity with theJournal’s style. Such editing will not affect thescientific content.

Manuscript PreparationManuscripts should be double-spaced andbetween 1,000 and 4,000 words. The manuscriptmust be sent by e-mail attachment (Word orRich Text Format only). An abstract of up to 500words should be provided, and a statement thatthe study was approved by the relevant researchethics board should be included, where relevant.

The lead author should also provide a brief biosketch and high-resolution photo of himself orherself (see details regarding illustrationsbelow).

ReferencesReferences should be numbered consecutivelyin the text by superscript numerals.Corresponding references should be listed at theend of the text. Exhaustive lists of references arenot encouraged. Unpublished sources such aspersonal communications should be citedwithin the text and not included in the referencelist.

The sequence for journal references should beas follows: author(s); title of paper; journalname abbreviated as in the Index Medicus; yearof publication, volume number, first and lastpage numbers. When there are more than threeauthors, shorten to three and add “et al.”

Col NF, Eckman MH, Karas RH, et al. Patientspecific decisions about hormone replacementtherapy in postmenopausal women. JAMA1997;277:1140-7.

The sequence for chapters of a book should beas follows: author(s) of chapter, chapter title,

author(s) of book, book title, edition, place ofpublication, publisher, year of publication, pagenumbers.

Galloway AC, Colvin SB, Grossi EA, et al.Acquired heart disease. In: Schwartz SI, ShiresGT, Spencer FC, eds. Principles of Surgery, 6thedition. New York: McGraw-Hill; 1994:845-99.

Tables and illustrationsEach table should be typed on a separate page,and should have a legend at the top indicatingthe information contained.

Illustrations may be sent electronically as a TIFFor JPEG file on a disk or CD. Do not embedimages, etc., in text files. Note: Figurereproduction cannot improve on the quality of theoriginals.

Numbers, units, and abbreviationsMeasurements are to be metric. In scientific text,physical quantities and units of time should beexpressed in numerals, for example, 2 kg, 6mmol, 5 hours, 4°C. Use only standard abbreviations, and avoidusing abbreviations in the title. Define allabbreviations on their first mention.

PermissionsWritten permission must be obtained formaterial that has been published in copyrightedmaterial; this includes tables, figures, and quotedtext that exceeds 150 words. Signed patientrelease forms are required for photographs ofidentifiable persons. A copy of all permissionsand patient release forms must accompany themanuscript.

Please submit manuscripts to:Dr Hubert [email protected]

Only electronic submissions will be accepted.

Canadian Journal ofRestorative Dentistry & Prosthodontics

Publication officielle de l’Académie canadiennede dentisterie restauratrice et de prosthodontie

Journal canadien dedentisterie restauratrice et de prosthodontie

The official publication of the Canadian Academy ofRestorative Dentistry and Prosthodontics

INSTRUCTIONS TO AUTHORS

Le journal canadien de dentisterie restauratrice etde prosthodontie publie des articles revus par despairs. Le Journal est principalement électroniqueayant ses articles intégraux en ligne. De plus, uneversion papier des abstraits de chacun des articlesest envoyée à tous les membres de l'ACDRP, auxsouscripteurs à la version papier, ainsi qu'auxinstitutions et associations. Le Journal accepte lesarticles de recherche, les revues, les articlesscientifiques, les rapports de cas, les résumés delivre, les anecdotes historiques, les trucscliniques, les lignes directrices, les lettres àl’éditeur et ainsi de suite. Les conditionsessentielles correspondent aux « Exigencesuniformes pour les manuscrits soumis à desrevues médicales » (http://www.icmje.org). Lespolitiques en matière d’éditorial pour la revuesont celles adoptées par le Conseil des éditeurs en sciences (http://www.councilscienceeditors.org/services/draft_approved.cfm). LeJournal sanctionne l'énoncé CONSORT(www.consort-statement.org) ayant trait auxnormes pour l'amélioration de la qualité desrapports d'études sur les essais cliniquesaléatoires.

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OCCLUSION


Myths of Orthodontic Gnathology/Mythes de la gnathologie orthodontique

By Donald J. Rinchuse and Sanjivan Kandasamy

About the Authors

Donald J. Rinchuse is a clinical professor at the School of Dental Medicine, University of Pittsburgh and in private practice inGreensburg, PA.

Sanjivan Kandasamy is a clinical senior lecturer in orthodontics, Dental School, The University of Western Australia; private practice,Perth, WA, Australia; and adjunct assistant professor in Orthodontics, Centre for Advanced Dental Education, St. Louis, MO.

ABSTRACTBy Dr. Kim Parlett, DDS, MScThe purpose of this article is to dispel and debunk 10 myths of orthodontic gnathology. The authors have recently written on manytopics dealing with orthodontic gnathology, and this article will help to more clearly elucidate and integrate the topics to explainthe ‘‘big picture.’’ The 10 myths of orthodontic gnathology are as follows:

Myth 1. Occlusion and condyle position are the primary causes of temporomandibular disorder (TMD). Occlusion and condyleposition are believed to have only secondary roles in the etiology of TMD and thus treatment of TMD has evolved to a biopsychosocial-medical model.

Myth 2. Orthodontics causes TMD. Orthodontic finishing and certain mechanics have been blamed for the development of TMDbut the evidence-based view is that TMD is not caused by orthodontics.

Myth 3. The modern view of TMD treatment is based on gnathologic principles. The current view of TMD treatment is based onthe “biopsychosocial model.

Myth 4. Orthodontic gnathology recognizes and evaluates patients’ parafunction and chewing cycle kinematics. The authors argue that the use of semi adjustable articulators in themselves do notlead to an evaluation of function.

Myth 5. A ‘‘high’’ restoration provokes TMD, but they are not primary to the development of TMD.

Myth 6. TMD asymptomatic subjects with internal derangement (ID) need treatment. The evidence-basedview is to let “sleepingdogs lie.”

Myth 7. Centric relation (CR) is the key to the diagnosis and treatment of TMD. The historical interpretation and semantics of CRis discussed and discredited as well as the reproducibility and significance of bite registration techniques anddeprogramming.

Myth 8. Canine protected occlusion (CPO) is the preferred functional occlusion type toward which to direct orthodontic patienttreatment. Group function and balanced occlusion appear to be acceptable occlusal schemes. It is highly variable and dependant on the individual circumstances.

Myth 9. Articulators play a critical role in orthodontic diagnoses. Several published articles by the authors have been critical of the use of articulators for orthodontic diagnoses relative to CR and kinematics.

Myth 10. Many valid scientific studies support orthodontic gnathology.

Guest Co-editor’s NoteThe authors use an extensive list of citations toapply an evidence-based model to theirarguments. In so doing they cover many of theissues that are pertinent to not justorthodontics but all dentistry! Without

sufficient research, conflicting treatmentmethodologies and outcomes we struggle withthese questions everyday in clinical practice.The authors are critical of orthodonticgnatholgy and gnathology in general in theirarticle. It leaves the reader questioning the

importance of many of the basic standards oftreatment that we have become accustomed to!

It is our hope that it reprinting this article willstimulate dialogue amongst our readership forfuture postings.

RINCHUSE AND KANDASAMY

Dr. Beverly McCollum established theGnathologic Society in 1926. Gnathology

is defined as ‘‘the science that treats the biologyof the masticatory mechanism as a whole: thatis, the morphology, anatomy, histology,physiology, and the therapeutics of the jaws ormasticatory system and the teeth as they relateto the health of the whole body, includingapplicable diagnostic, therapeutic, andrehabilitation procedures.’’1

Many gnathologic research endeavors haveadded much to our knowledge andunderstanding of the stomatognathic system,particularly those involving chewing(masticatory) kinematics2–13 and the earlyintraoral telemetry studies (to cite only afew).14–17 Although originally founded onscientific principles, the application of thevalid gnathologic research to clinical practicehas moved away from these founding tenets.

Modern clinical gnathology (vs university-based gnathologic research) has become, forthe most part, a pseudo-science based onmechanistic, perfunctory procedures, andinstrumentation.

There are many contemporary occlusalinstitutes that clearly have perverse views ongnathology that are not evidence-based. Dr. Lysle Johnston18 sarcastically stated that


Note du co-rédacteur invitéLes auteurs utilisent une liste exhaustive decitations pour corroborer leurs argumentsselon un modèle fondé sur les preuves. Cefaisant, ils ont abordé non seulement les sujetspertinents à l’orthodontie, mais aussi à tous lesdomaines de la Médecine dentaire. En

l’absence de recherche suffisante, noussommes aux prises avec des méthodologiesthérapeutiques et des résultats contradictoireschaque jour en pratique clinique. Les auteursexaminent d’un œil critique la gnathologieorthodontique et la gnathologie en généraldans leur article. Le lecteur doit alors se

questionner sur l’importance des normes debase thérapeutiques auxquelles nous sommeshabitués.

Nous espérons que la réimpression de cetarticle encouragera le dialogue et la rédactiond’articles parmi nos lecteurs.

RÉSUMÉPar Dr Kim Parlett, DMD, MScLe but de cet article est de réfuter 10 mythes de la gnathologie. Les auteurs ont traité de plusieurs sujets concernant la gnathologieorthodontique, et cet article permettra de mieux cerner la situation dans son ensemble. Les 10 mythes sont les suivants :

1er mythe. L’occlusion et la position du condyle sont les causes principales du trouble de l’articulation temporomandibulaire (ATM).On est d’avis que l’occlusion et la position du condyle jouent un rôle secondaire dans l’étiologie du trouble de l’ATM. Parconséquent, le traitement du trouble de l’ATM a évolué vers un modèle biopsychosocial et médical.

2e mythe. Le traitement en orthodontie est la cause du trouble de l’ATM. On blâme les soins orthodontiques et certaines techniques comme étant la cause du trouble de l’ATM, mais l’opinion fondée sur les preuves vient contredire ce mythe.

3e mythe. La façon moderne de traiter le trouble de l’ATM est fondée sur des principes de gnathologie. La façon courante est fondée sur le modèle biopsychosocial.

4e mythe. La gnathologie orthodontique reconnaît et permet d’évaluer la parafonction et le mouvement mandibulaire lors de lamastication. Les auteurs soutiennent que l’utilisation d’articulateurs semi-ajustables ne mène pas à une évaluation dela fonction.

5e mythe. Une restauration « haute » provoque le trouble de l’ATM, mais n’est pas primaire au développement du trouble de l’ATM.

6e mythe. Les sujets qui ne ressentent pas de symptômes du trouble de l’ATM en présence d’affection interne ont besoin d’être traités. Les preuves factuelles révèlent qu’il « ne faut pas réveiller le chat qui dort ».

7e mythe. La relation centrique (RC) est la clé du diagnostic et du traitement du trouble de l’ATM. L’interprétation historique et lasémantique de la RC est discutée et discréditée ainsi que la reproductibilité et la signification des techniques d’enregistrement de l’occlusion et de déprogrammation.

8e mythe. La protection canine est le type d’occlusion fonctionnelle préférée vers lequel vous voulez diriger le traitement orthodontique. La fonction de groupe et l’occlusion équilibrée semblent être des systèmes occlusaux acceptables. C’esttrès variable et fonction des particularités individuelles.

9e mythe. Les articulateurs jouent un rôle essentiel dans les diagnostics en orthodontie. Plusieurs articles publiés par des auteursont critiqué l’utilisation des articulateurs pour les diagnostics en orthodontie en ce qui concerne la relation centrique et la cinématique.

10e mythe. Plusieurs études scientifiques valides appuient la gnathologie orthodontique.

The article below is reprinted with permission from the American Journal of Orthodontics and Dentofacial Orthopedics 2009;136(3):322–30.


MYTHS OF ORTHODONTIC GNATHOLOGY

‘‘gnathology is the science of how articulatorschew.’’ In the 1970s, Roth formally introducedthe classic principles of clinical gnathology toorthodontics (orthodontic gnathology).19–21

The notions and considerations of modernorthodontic gnathology are not based onprinciples of science and do not correspond tocontemporary evidence-based thinking. Theremight not be a unified orthodonticgnathologic view, but it seems that the oneestablished by Roth is by far the most notable.

In general, the objectives of modern clinicaland orthodontic gnathology are (1) toestablish coincidence of maximumintercuspation (or centric occlusion) withcentric relation (CR) in an anterosuperiorseated condylar position, (2) to attain canine(mutually) protected occlusion (CPO) andanterior guidance, and (3) to mountpretreatment diagnostic casts on a fullyadjustable articulator (with some alsorecommending pantographic tracings andmany recommending deprogramming beforetaking centric-bite registrations).19–24

Gnathologists believe that failure to achieve atleast 1 of these objectives will predisposepatients to signs and symptoms oftemporomandibular disorders (TMDs).19–21

The purpose of this article is to dispel anddebunk 10 myths of orthodontic gnathology.We have recently written on many topicsdealing with orthodontic gnathology, and thisarticle will help to more clearly elucidate andintegrate the topics to explain the ‘‘bigpicture.’’22 –29 The 10 myths of orthodonticgnathology are (1) occlusion and condyleposition are the primary causes of TMD, (2)orthodontics causes TMD, (3) the modernview of TMD treatment is based ongnathologic principles, (4) orthodonticgnathology recognizes and evaluates patients’parafunction and chewing cycle kinematics,(5) a ‘‘high’’ restoration provokes TMD, (6)TMD asymptomatic subjects with internalderangement (ID) need treatment, (7) CR isthe key to the diagnosis and treatment ofTMD, (8) CPO is the preferred functionalocclusion type toward which to directorthodontic patient treatment, (9) articulatorsplay a critical role in orthodontic diagnoses,and (10) many valid scientific studies supportorthodontic gnathology.

MYTH 1: OCCLUSION AND CONDYLEPOSITION (CR POSITION) ARE THE PRIMARY CAUSES OF TMDOcclusion and condyle position were once thought to be the primary causes ofTMD.19–22,30,31 The temporomandibular joint(TMJ) pain dysfunction syndrome wasthought to be a distinct disease caused by 1etiologic agent (eg, occlusion or stress; later, itwas thought to be caused by an eccentriccondyle position).32–34 However, past etiologicagents such as occlusion and condyle positionhave not been proven to be the primary causeof TMD.35–49 Furthermore, TMD etiology anddiagnosis are complicated because manydiseases and dysfunctions can affect the TMJcomplex and the neighboring structures of thehead and neck.23–26,50 TMD is now considereda collection of 6 subclasses of diseases anddysfunctions, with many causes for eachsubclass.39,40 TMD treatments have changedfrom a dental-based model (ie, classic dental and jaw causative theories) to abiopsychosocial-medical model thatemphasizes orthopedics, neuroscience, chronicpain theory, sleep neurophysiology, genetics,and psychosocial factors.51–70 Becauseocclusion and condyle position are currentlybelieved to have secondary roles in the etiologyof TMD, these should reduce the significanceof the orthodontic gnathologic view;gnathology is very much occlusion andcondyle position oriented.23–26,28,29

MYTH 2: ORTHODONTICS CAUSES TMDThe orthodontic gnathologic view has arguedthat orthodontic treatment causes TMD from2 possible perspectives. First, it causes TMD indirectly because nongnathologicorthodontists do not achieve a gnathologicocclusal finish and thereby produce aniatrogenic functional occlusion (ie, functionalbalancing interferences) and eccentric condyle(or CR) position that predisposes to TMD.The other possibility is that certainorthodontic appliances or techniques (eg,Class III mechanics, extractions, chin cups,and so on) directly cause TMD.19–22,28,29

However, the evidence-based view clearly isthat orthodontic treatment does not causeTMD.71-75 This should have been a tremendouswakeup call to the premises of clinicalgnathology that are clearly dental-based.Parenthetically, because the datademonstrating that orthodontic treatment

does not cause TMD are population-based, itis still possible for an occasional orthodonticpatient’s TMJ complaint to be caused bytreatment.

MYTH 3: THE MODERN VIEW OF TMDTREATMENT IS BASED ON GNATHOLOGIC PRINCIPLES (DENTALBASED)Contemporary TMD treatment has movedaway from a historic, mechanical, dental-based model, no longer involving occlusalmodification or jaw-repositioning protocols.50,65,66

The current evidence-based view of TMDtreatment is now a biopsychosocial model.51–64 Dworkin76 stated that ‘‘the biopsychosocialmodel remains the best approach to gainingan understanding for how to integrate the hostof biologic, clinical and behavior factors thatmay account for the onset, maintenance andremission of TMD, as well as forunderstanding how to make rational choicesfor treatment.’’ Genetics related to pain andimaging of the pain-involved brain, centralbrain processing of thinking and emotions,endocrinology, and so on, are the excitingfuture. Treatments that are effective for allforms of chronic pain are equally effective inmitigating TMD pain.54,63,65,66 Cognitivebehavioral therapies and biofeedback arebecoming the recognized initial and earlytreatment modalities for TMD.51–53,55,56,63,64

However, there is support for the belief thatocclusal splints (stabilizing-type splints arerecommended) work best initially, andcognitive behavioral therapies andbiofeedback work better later.56,59–61 Cognitivebehavioural therapies involve many treatmentsemphasizing stress reduction and cognitiveawareness: education regarding mind-bodyrelationships with stress management,relaxation training, distraction and pleasantactivity scheduling to reduce the impact ofpain on activities, cognitive restructuring, self-instructional training, and maintenanceskills.64

MYTH 4: ORTHODONTIC GNATHOLOGYRECOGNIZES AND EVALUATES PATIENTS’ PARAFUNCTION AND CHEWING CYCLE KINEMATICSTwo important aspects of human jaw functionare not evaluated by the orthodonticgnathologic approach, particularly in relationto articulator mountings: parafunction and


chewing cycle kinematics. The harshest andperhaps the most destructive occlusal forcesare produced from parafunction—bruxingand clenching.77

In this regard, it seems that it is not so muchthe type of occlusion or CR position that aTMD patient has as it is how the patient useshis or her teeth and jaws.22–24 Patients withoptimal and ideal static and functionalocclusions (or condyle positions) have TMD,and vice versa. This stresses the importance ofproperly evaluating a patient’s parafunctionirrespective of the type of occlusion or condyleposition. Incidentally, it was once incorrectlythought some 50 years ago during the‘‘occlusionist’’ era (and still espoused today)that parafunction was caused by occlusalprematurities or interferences and thatbruxing was nature’s attempt to resolve theocclusal problems by grinding them away.Current evidence clearly supports the notionthat parafunctional habits are basically acentral nervous system phenomenon(mediated by the limbic system) and not ofocclusal origin.78–85

The other aspect of human jaw function thatis not evaluated by orthodontic gnathology(particularly by articulator mountings) ischewing cycle kinematics. It is understood thatthe chewing pattern shape as viewed from thefrontal aspect is described as a tear drop.2,4,43

There are about a half dozen different chewingpatterns.2–4,23,24 This elliptical chewing motioncan vary significantly from person to person.2,4

Simply stated, some patients have a morevertical chewing pattern; in others, it can bemore horizontal.2,4,24 Chewing kinematics canvary based on several factors such as age,dental static occlusion, facial morphology, andso on.2–4,43,85 For instance, in the developmentalstage of the deciduous dentition, chewingpattern shape (judged from the frontal aspect)is very much lateral, with the mandible circlingout on opening and circling inward (medially)on closing in a narrow and tight loop.4 In thedevelopmental stage of the permanentdentition, chewing pattern shape (judgedfrom the frontal aspect) is not nearly as lateral;on opening, the mandible circles inward(medially) and, on closing, circles outward(laterally) in a larger loop than that in thedeciduous dentition.4 The length of thechewing stroke is approximately 16 to 19 mm

with about 20 masticatory strokes beforeswallowing, taking about 12 seconds.4 Theconsistency and shape of chewing kinematicsvary for patients with deep bitemalocclusions.86 A logical hypothesis might bethat those with more vertical chewing patternshapes adapt best to CPO, whereas those withmore horizontal chewing patterns functionbest with group function or balancedocclusions.24

With the above in mind, how does theorthodontic gnathologic approach (andarticulator recordings and mountings)account for, and take into consideration, eachpatient’s parafunction and chewingkinematics?

MYTH 5: A ‘‘HIGH’’ RESTORATION PROVOKES TMDIn 1995, Roth87 wrote: ‘‘I would like to have theopportunity of placing a ‘high molarrestoration with balancing interferences’ in themouths of all who believe that occlusion hasnothing to do with TMD.’’ He used thisintuitively appealing argument to support thenotion that occlusal interferences are theprimary cause of TMD. Certainly, it would beillogical to argue that gross occlusaldisharmonies would not adversely affect thestomatognathic system and potentially havesome negative impact on the TMJs. Themodern evidence-based paradigm does notargue that occlusal interferences (this is insharp contrast to balancing contacts that aregenerally considered benign and typically donot need occlusal adjustments) are no longera possible etiologic agent for TMD. Theargument is that they now are not primary andhave a lesser (secondary) role than oncethought. Occlusal equilibration of grossocclusal prematurities is still within the realmof evidence-based care.22–27,88 The occlusalprovocation studies (provoked or producedocclusal interferences in subjects) are equivocalas to the role of high restorations causingTMD.89–92

TMD is certainly a potential consequence of aprovoked high restoration, but so areheadaches, tooth mobility, fremitus, and so on.Furthermore, most occlusal provocationstudies are biased because they typically useddental students (or nurses) as subjects whohad some notion of the possible outcome of

the intervention.

Curiously, some subjects in their controlgroups (with no high restorations) also hadsome of the same outcomes (eg, headachesand TMD) as those in the experimental group.Increasing the vertical dimension of occlusiondoes not generally negatively impact the TMJsunless there is a preexisting ID.93–96

MYTH 6: TMD ASYMPTOMATIC SUBJECTS WITH ID NEED TREATMENTIt has been estimated that as many as 30% ofTMD asymptomatic subjects have ID.97-99 Theissue becomes whether TMJ ID predisposeTMD asymptomatic subjects to TMD later on.And if this is true, the next question is whetherthese subjects need some form of dental ororthodontic treatment to mitigate futureTMD. A relationship (studies wereassociational and not cause-and-effect) hasbeen established between TMJ ID andcraniofacial morphology (although thedifferences were small).100–102 TMJ discabnormality was associated with reducedforward growth of the maxillary andmandibular bodies; for adolescents, there wasreduced growth of the mandibular ramus.100,103

It is not a leap of faith to believe that TMJ discpathology can affect condylar growth.100 It hasbeen hypothesized that untreated (orinadequately treated) TMJ ID will most likelylead to pain, degenerative joint disease,compromised mandibular growth, and othernegative conditions.103,104

There is general agreement that someconsideration of this information should befactored into an orthodontist’s thoughtprocess during treatment planning.100–102

Nonetheless, the orthodontic gnathologycamp (Dr Kazumi Ikeda105) argued that thesesubjects need treatment involving a nighttimeocclusal stabilizing splint initially (in the past,the argument was for repositioning splints)followed perhaps by comprehensiveorthodontic treatment. Roth87 alwayscontended that it is not just good enough tomaintain a patient’s status quo as related toTMJ health, but orthodontists have a higherobligation—to improve their patients’ TMJhealth status.

It is believed that the best time to treat ID isearly, before significant disc, skeletal, and




occlusal changes occur while patients haveoptimal capacity for tissue repair and growth:ie, when they are young.103 In addition, it isbelieved that most initially asymptomaticpatients will become symptomatic usuallyafter growth is complete and when the TMJshave progressed to a nonreducing discdisplacement and degenerative joint disease; atthis stage, treatment would be significantly lesseffective.103,104 The contending view, andperhaps the logical and evidence-based view,is to ‘‘let sleeping dogs lie’’ and not to treatthese patients because they are TMJasymptomatic.106,107 To treat these patientsmight do more harm than good, since thereseems to be no practical and evidence-basedtreatment options for correcting these TMJanatomic disc derangements. In addition, noscientific evidence shows that treatment willmitigate future TMD. Furthermore, therelationship of disc displacement to pain,mandibular dysfunction, osteoarthrosis, andgrowth disturbances is unclear.106 Not allgrowing patients with disc displacements growabnormally, nor do all patients with growthdeficiencies have disc displacements.54,107,108

Interestingly, it was also demonstrated thatpatients with moderate to severe TMD withassociated disc displacement withoutreduction will improve without treatment overa 2.5-year period.108 It would seem that, if discdisplacement were a significant cause ofmandibular growth deficiency, its signs andsymptoms would be more common in thispopulation than in the normal population.Finally, the relationship between discdisplacement and TMD is complex; the causesare multifactorial (eg, trauma, genetics, stress,and pathology) and therefore cannot besimply explained by disc displacement.107

MYTH 7: CR IS THE KEY TO THE DIAGNO-SIS AND TREATMENT OF TMDRoth87 stated: ‘‘If condylar position is notimportant in orthodontics, how did the term‘Sunday Bite’ ever arise?’’ CR has been definedin so many different ways that it has lostcredibility.109 The concept of CR hashistorically and arbitrarily migrated from aposterior to a posterosuperior position torecently the most anterosuperior position ofthe condyles in the glenoid fossa.23 It would bedifficult to prove that any CR position iscorrect for all patients. There appears to be arange of CR positions. In this respect, one

study found that 89% of condyles were notconcentric.110 It seems that mid to anteriorsagittal CR positions might be better than aretruded position; however, in some patients,a retruded CR is the healthy norm.99,111 TheAmerican Dental Association in TMDconference reports in 1983 and 1990 statedthat ‘‘there is insufficient evidence thateccentricity of the condyles in the glenoid fossawill predispose to TMD or any other healthconsequence.’’39,40 Johnston18 sarcasticallywrote about the absurdity of the many falsenotions of CR: ‘‘it could be argued that theprogressive modification of Centric Relation(definition) has done more to eliminatecentric slides than 20 years of grudgingacquiescence to the precepts of gnathology.’’The gnathologic view dictates that maximumcuspation, or centric occlusion, should becoincident with CR (anterosuperior).2–4 In theearly 1970s, Roth19–21 argued that the correctCR position was a retruded, posterosuperiorposition. Early intraoral telemetry studies didnot support the concept of a retruded CR.14–17

Roth’s view (and that of gnathology per se)was proven fallacious, and he recanted hisprevious view of retruded CR and adopted thecontemporary view of anterosuperior CR.19–23

The past notion of retruded (posterosuperior)CR by the orthodontic gnathologists waswrong despite the sad fact that manyorthodontists blindly followed this thinkingfor decades. How much confidence andcredibility should we have for orthodonticgnathology with its mired history and falsethinking? Furthermore, what happened toorthodontic gnathology patients treated to theold retruded centric position? Did theydevelop TMD? There are also many problemsand issues related to CR records. As Nuelle andAlpern112 wrote: ‘‘Doctor selected TMJpositioning at the dental chair is a blindprocedure.’’ Centric records have been shownto be somewhat reliable, but their validity hasnot been substantiated.22,23 The orthodonticgnathologic view that claims that the Roth‘‘power centric bite registration’’ seats patients’condyles in an anteroposterior CR needs to beverified by magnetic resonance imaging data.This becomes especially important becauseAlexander et al113 clearly demonstrated in amagnetic resonance imaging study thatcondyles are not exactly located in the CRpositions that clinicians believe them to be.

In addition, how do we know which of themany promulgated CR recordings (andpositions) is correct? In this respect, there areat least 6 occlusal philosophies in dentistry(not limited to orthodontics).28 Five of the 6views can be considered gnathologically basedviews: classic gnathology (dating back toStallard, Stuart, Thomas, and Lucia);bioesthetic dentistry (based on the work ofRobert L. Lee); Dawson, Pankey Institute;neuromuscular school (Las Vegas Institute,Jankelson Myotronics view); and the Rothorthodontic gnathologic view. The sixth viewis the nongnathologic view, which essentiallysupports taking a reliable centric occlusion(maximum intercuspation) bite registration ashas been traditionally done for the last century.Of course, there can be many variations of thisnongnathologic view. The various occlusalschools differ mainly on their view of CR—itsposition, but more so on how it is recorded.There are various philosophies concerningmanipulation techniques to record CR,deprogramming, and whether to use afacebow or an earbow transfer. So, eachocclusal philosophy is competing with theothers on the proper definition and correctrecording technique of CR; this furthercomplicates and muddles the issue of CR,making any 1 view less valid and important.

MYTH 8: CPO IS THE PREFERRED FUNCTIONAL OCCLUSION TYPE TOWARD WHICH TO DIRECT ORTHODONTIC PATIENT TREATMENTWe have discussed the problems with thenotion of ascribing to the philosophy andconcept of CPO for all orthodontic patientsand treatments.24 A summary of what wewrote in this comprehensive article follows.

CPO, as the optimal type of functionalocclusion to establish in orthodontic patients,is equivocal. Woda et al114 wrote, after acomprehensive review of the literature, ‘‘Purecanine protection or pure group functionrarely exists and balancing contacts seem to bethe general rule in the population ofcontemporary civilizations.’’ Modern evidencedoes not support a view that blindly adheresto the concept of CPO for all patients.

One type of functional occlusion should notbe considered optimal and preferred for allpatients. CPO is merely 1 of a few possible


functional occlusion schemes that might beattained with orthodontic treatment. Subjectswith normal static occlusion (or Class Iocclusions) tend to have balanced occlusion orelse group function, and not CPO.115,116 Groupfunction and balanced occlusion (with nointerferences, only balancing contacts) appearto be acceptable functional occlusion schemes,depending on the patient’s uniquecharacteristics. The stability and longevity ofCPO is questionable. Reestablishing functionalocclusion through orthodontic treatment backto the original type before treatment isproblematic, since orthodontic treatment isoften started before the permanent canineshave fully erupted. It would also appear thatconsideration of chewing cycle kinematics,craniofacial morphology, static occlusion type,current oral health status, and parafunctionalhabits might provide important and relevantinformation about the most suitablefunctional occlusion type for each patient.24

MYTH 9: ARTICULATORS PLAY A CRITICAL ROLE IN ORTHODONTIC DIAGNOSESWe have written several evidence-basedreviews that argued against the validity ofarticulators in orthodontics.22,28,29 Therefore,this section will merely summarize somepertinent points in these articles. There aremany types of articulators: arcon, nonarcon,fully adjustable, semi-adjustable, polycentrichinge, and so on. Alpern and Alpern117

presented a strong argument that thepolycentric hinge articulator might have someadvantages over the others. Articulators can beuseful for gross fixed and removableprosthodontic and orthognathic surgicalprocedures to at least maintain a certainvertical dimension while preclinical laboratoryprocedures are performed on dental casts. Amain criticism of articulators in orthodonticsis based on the study by Lindauer et al.118 Theyfound that, during opening and closing, thecondyles not only rotate but simultaneouslytranslate (move downward and forward);there is an instantaneous center of rotation.Articulators are based on the faulty notion ofa ‘‘terminal hinge axis,’’ which goes back to ahalf-century-old claim of Posselt, that, in theinitial 20mmor so of opening and closing, themandible rotates similarly to a door hinge(and does not simultaneously translate).118

However, Posselt formulated his view when

CR was viewed as a posterosuperior, retruded(and not anterosuperior) CR position, and,during the recording of CR, distally guidedpressure was applied to the chin, the mostobvious reason for Posselt’s finding of a‘‘terminal hinge axis.’’22 Furthermore, Mohl35believed that the sensitivity and specificity ofarticulator-mounted casts in the diagnosis ofTMD are poor. In addition, there is no validevidence that performing articulatormountings improves patients’ stomatognathichealth. Interestingly, one of the most reliableand valid reports by the orthodonticgnathologic camp states that the differencebetween gnathologic and nongnathologicdiagnostics is perhaps 1 to 2 mm, and this isonly in the vertical plane.119 Also, articulatorscannot accurately simulate jaw movements.Bite registrations are static, and patients arenot asked to chew or function. There is noproven validity of bite registrations and wherethe condyles are located as a consequence ofsuch recordings. Articulator mountings, forthe most part, have not been shown to affectorthodontic diagnoses or treatment plans.120

After all the effort involved in mounting andthe attention paid to the minute details ofocclusion and condylar position, littleconsideration is given to the physiologicadaptation of the dentition after posttreatmentocclusal settling. In children, the glenoid fossacomplex changes with growth; this impliesthat new mountings would need to beroutinely performed throughout treatment.Although argued by orthodontic gnathologistsas not true, it takes more time and cost toperform the mountings.22

MYTH 10: MANY VALID SCIENTIFICSTUDIES SUPPORT ORTHODONTICGNATHOLOGYWe have published our criticisms of manyorthodontic gnathology studies.22,25,28,29 Wewould, therefore, like to briefly address onlythe recent study of Cordray.121 First, few studiesare perfect and meet all requirements of greatresearch. However, the study by Cordray (andothers by orthodontic gnathologists) is moreproblematic than the typical published study.29

Cordray seemed to believe that it was possibleto evaluate and test the effect of‘‘neuromuscular deprogramming’’ (with atongue blade) on centric bite registrations.

However, the study design precluded such an

evaluation. Two independent variables(deprogramming and gnathologic biteregistration) were confounded andcommingled into 1 recording, so that thesingle, isolated effect of deprogramming alone(vs no deprogramming) could not beaccurately determined. To effectively ascertainthe true influence of deprogramming (if therewas one), a third group would have had to beadded—a gnathologic group withoutdeprogramming. In addition, Cordray claimedto support the view that orthodonticgnathology (with articulators) is valid becauseit can help to better discern and elucidate thecorrect orthodontic diagnosis (by correctlydetermining the so-called correct centric biteregistration). This conclusion was impossiblefor a number of reasons: not all the errors wereaccounted for, the large standard deviation wasnot explained, there were no blinding and noinformation on how the nongnathologiccentric records were performed, and so on.Furthermore, Cordray did not mention thecontradictory findings of Kulbersh et al122 andEllis and Benson.120 More importantly, even ifthere is a difference in centric recordings whendeprogrammed or gnathologically determined,there is the problem in assuming that thenewer, deprogrammed record is better (morephysiologic) than the original one.22,23,123

CONCLUSIONSIt is time to reconsider the validity of the age-old ideas of orthodontic gnathology that arebased on rhetoric, blind faith, art,emotionalism, and practice managementrather than on science and evidence.Orthodontic gnathologists have proved nohealth benefit to justify the many perfunctoryexercises of the philosophy. The focus oforthodontic gnathology (and the clinicalgnathologic view) was on the relationship ofocclusion, then condyle position, and nowTMJ disc position, dysfunction, and disease onthe stomatognathic system (particularlyregarding TMD). The view that occlusion andcondyle position are the primary causes ofTMD, and that diagnoses and treatmentsshould be based on these notions, has beendiscredited. There is little to no evidence thattreating subjects with TMJ ID will prevent ormitigate future TMD. If we are to embrace theconcept of ‘‘evidence-based’’ treatment, thespecialty will eventually have to carefullyevaluate the quality of the evidence and its




message within the context of a contemporaryorthodontic practice. The dated ideas and artof orthodontic gnathology may actually be awaste of time for the average orthodonticpatient. It is up to us to decide. In the end, theday-to-day application of any ‘‘philosophy’’must ultimately measure up with literaturethat is pertinent to orthodontics.

In orthodontics, everything ‘‘works’’ wellenough to support a practice. Thus, the factthat something is used ‘‘successfully’’ does notmean that it is correct. Gnathology may makethe orthodontist feel better; however, there islittle evidence that the same benefits accrue tothe patient.

DISCLOSUREThe authors report no commercial,proprietary, or financial interest in theproducts or companies described in thisarticle.

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119. Kulbersh R, Kaczynski R, Freeland T. Orthodontics and gnathology. Semin Orthod 2003;9:93-5.

120. Ellis PE, Benson PE. Does articulating study casts make a difference to treatmentplanning? J Orthod 2003;30:45-9.

121. Cordray FE. Three-dimensional analysisof models articulated in the seated condylar position from a deprogrammedasymptomatic population: a prospectivestudy. Part 1. Am J Orthod Dentofacial Orthop 2006;129:619-30.

122. Kulbersh R, Dhutia M, Mavarro M, Kaczynski R. Condylar distraction effectsof standard edgewise therapy versus gnathologically based edgewise therapy. Semin Orthod 2003;9:117-27.

123. Klasser GD, Greene CS. Role of oral appliances in the management of sleep bruxism and temporomandibular disorders. Alpha Omegan 2007; 100:111-9.


OCCLUSION

ABSTRACTThe concept of the occlusal compass was originally proposed by Michael H. Polz to help technicians wax-up occlusal forms of crowns.The movements of an antagonistic cusp across the occlusal table of a tooth are described with sequential waxing completed to allowproper clearance in all excursions. This article describes the use of the occlusal compass in the waxing of an upper and a lower 6-yearmolar. The concepts outlined can be applied to all restorative materials including amalgam, composite, gold, and porcelain.

RÉSUMÉLe concept du compas occlusal a été proposé au départ par Michael H. Polz pour aider les techniciens à préparer des modèles en cire deformes occlusales de couronnes. Les mouvements d’une cuspide antagoniste sur la face occlusale d’une dent sont décrits par cirageséquentiel complété pour permettre le jeu dans toutes les directions. Cet article décrit l’emploi du compas occlusal dans la préparationde modèles de cire d’une molaire de six ans de la mandibule supérieure et inférieure. Les concepts décrits peuvent s’appliquer à tousles matériaux de restauration y compris l’amalgame, le composite, l’or et la porcelaine.


Occlusal Function and the Single CrownFonction occlusale et couronne

By Mr. Paul Rotsaert RDT

About the Author

Paul Rotsaert, RDT is the President of Rotsaert Dental Laboratory, Hamilton, Ontario.

When we are taught tooth morphologythe emphasis is usually on the features

of each individual tooth. The functionalaspects are often glossed over or are presentedin a manner that causes a great deal ofconfusion. The concept of the occlusalcompass was proposed by Michael H. Polz tohelp technicians wax-up occlusal forms ofcrowns. The occlusal compass describes themovements of an antagonistic cusp across theocclusal table of a tooth.

In its basic form the occlusal compass is madeup of four movements of the mandible:protrusion, the forward movement of themandible; laterotrusion, the movement of themandible away from the midline;mediotrusion, the movement towards themidline; and lateroprotrusion, a combinedmovement with forward and lateralcomponents.

The three-dimensional pathways aredependent on the geometries of the anteriorguidance (lingual surfaces of maxillary

anterior teeth) and the posterior determinants(articular eminence, head of the condyle,condylar disc and other associated soft tissues).Figures 1 and 2 show these movements. Notethat these movements are paired: a rightlaterotrusion (teeth) and a left mediotrusion(condyle) are the result of the same movement.In the occlusal design concept the laterotrusiveside guidance (canine) will cause themediotrusive side to disclude. This protectionof the mediotrusive side is significant becausethis is the side where the condyle is translatingdown the eminence. Any mediotrusive contactcan cause significant deflections of the condyle,potentially leading to derangement of thetemporomandibular joint.

The advantage of working with full-archmodels that are facebow mounted is that theanterior guidance components are present andthus can be used to more accuratelyapproximate the movements of the patient’smandible. Having the guidance componentsfrom the right side is critical for simulating themediotrusive movement on the left side.

Figure 1. Mediotrusive, laterotrusive, andprotrusive movements of the mandible and teethsuperimposed.

Figure 2. Mediotrusive and protrusive movementsof the mandible.

ROTSAERT

Anterior guide tables on articulators can helpwhen the anterior guidance is missing orincomplete. Ideally correct sagittal condylarinclinations can be recorded usingcondylography.

Figure 3 illustrates the pathways of theopposing cusp tips on the right side of thediagram; on the left side the colour coding ofthe teeth represents the parts of the occlusalsurfaces that are significantly influenced bythe specific movement.

Figure 4 takes the view of the occlusalcompass to the individual first molars. Thepatterns illustrate the waxing sequence forthe development of the occlusal surfaces. Bywaxing the occlusal morphology cusp by cuspwe are able to focus on the specific pathwaysthat influence the morphology of each cusp.

The stamp cusps that land in the center of theopposing teeth have the greatest influence onthe occlusal morphology. In the example ofan Angle Class I occlusal scheme it is themiddle buccal cusp of the lower molar (thestamp cusp) that drives the occlusalmorphology of the upper molar. The key todeveloping the occlusal morphology islocating the occlusal stop on the occlusaltable. In this example a single stop is waxedand based on its position it is connected toone of the triangular ridges. The cusppositions are then sketched in (Figure 5). Thetwo buccal shear cusps of the upper molar arepositioned so that the middle buccal cusp ofthe lower molar moves between them in thelaterotrusive movement (Figures 6 and 8).The mesiolingual cusp of the upper molar ispositioned in the central fossa area of thelower molar so that the cusp moves betweenthe two lingual shear cusps of the lower molarin laterotrusion (Figure 7). It is veryimportant to verify the mediotrusiveexcursion (Figure 9) and modify the positionso that there are no contacts in this excursivemovement.


Figure 3. A and B, Illustration of pathways of the opposing cusp tips on the right side of the diagram: onthe left side, the colour coding of the teeth represents the parts of the occlusal surfaces that aresignificantly influenced by the specific movement.

Figure 4. A and B, View of the occlusal compass to the individual first molars.

Figure 5. Occlusal view of cusp sketches. Figure 6. Buccal view maximum inter-cuspalposition.

Figure 7. Lingual view maximum inter-cuspalposition

Figure 8. Buccal view laterotrusion.

Figure 9. Lingual view mediotrusion.

Figure 10. A and B, Development of the cusp morphology of the upper molar.

A B

A B

A B


OCCLUSAL FUNCTION AND THE SINGLE CROWN

Once the cusp tips have been located, theprocess of developing the morphology ofeach cusp can begin (Figure 10).

The mesiobuccal cusp of the upper molar isgreatly influenced by the lateroprotrusivemovement; thus the yellow colour coding(Figure 11A and B). Care must be taken notto make this cusp too tall, and it is importantto ensure that the triangular ridge issomewhat flat. This shape is needed so thatthe lower cusp can move from the holdingstop without contact in the entire range ofmovement from protrusion to laterotrusion.Once the triangular ridge is completed, therest of the cusp can be formed including themesial marginal ridge (Figure 11C).

The distal buccal cusp is more influenced bythe laterotrusive movement (blue; Figure 12Aand B). The height of this cusp can be higher

than the mesial cusp and the form of thetriangular ridge can be much higher as well(Figure 12C). This cusp will also tie into thedistal aspect of the mesial lingual cusp toform a transverse ridge. The addition of thesmall lobe mesial from the main body of thetriangular ridge creates the larger volumecharacteristic of this cusp. The mesial anddistal aspects of the cusp are filled in tocomplete the cusp form as well as the distalmarginal ridge.

This completes the buccal shear cusps; notethe differences in the forms as generated bythe influence of the two dominantmovements.

The mesial lingual cusp is most influenced bythe mediotrusive movement in the occlusaltable (Figure 13A and B). The lingual side ofthis cusp is influenced by the laterotrusivemovement where it will pass between the

lingual cusps. The mediotrusive movement isfrom the holding stop moving mesially andlingually. This requires the surfaces in thisdirection to be clear of obstructions. Thedistal aspect can be much higher and createdwith greater volume as there is minimalopposing tooth structure in this area (Figure13C). The triangular ridge is very shallow andas it develops toward the central fossa itdiminishes in size. The small auxiliary ridgeradiates from the central fossa and progressesout to the mesiodistal of the occlusal table.This creates a groove that tracks themediotrusive movement acting as a sluicewayfor food during mastication.

The distolingual cusp is almost anafterthought as it may or may not occludewith the opposing tooth. In some patientsthis cusp is minimal or missing on secondand third molars. It is not significantlyinfluenced by a major opposing cusp and is

Figure 11. A–C, Mesiobuccal cusp of the upper molar.

Figure 12. A–C, Distal buccal cusp of the upper molar.

Figure 13. A–C, Mesial lingual cusp of the upper molar.

A B C

A B C

A B C

ROTSAERT

thus assigned the colour grey (Figure 14). InAngle Class II cases there will be more of aninfluence from the middle buccal cusp of thelower molar. A small triangular ridge and adistal ridge define the form of this cusp.

This completes the forming of the lingualstamp cusps and the occlusal form of theupper molar. The development of theocclusal morphology using this methodshould generate a form that is withoutexcursive contacts and blends with the

adjacent dentition.

The development of the occlusal morphologyof the lower first molar follows a similarsequence (Figure 15).

Again, the first step is to locate the positionof the holding stop of the mesiobuccal cuspof the upper molar. The cusps are sketched intaking into account the excursive movements.The heights and position of the two lingualshear cusps are established by thelaterotrusive movement of the mesial lingualcusp of the upper molar passing betweenthem. The main stamp cusp (middle buccalcusp) reaches for the central fossa of theupper molar. The laterotrusive andmediotrusive movements are checked forinterferences. The mesial buccal cusp ispositioned so that it contacts the mesialmarginal ridge of the upper molar (Figure16). There are no significant movementsassociated with this cusp. It is important tosee that none of the basic cusp forms contactany of the opposing teeth in the excursions.

The distolingual cusp is the shear cusp mostinfluenced by the lateroprotrusive movementand will have similar attributes to themesiobuccal cusp of the upper (Figure 17Aand B). This cusp is smaller and flatter whencompared to the mesiolingual cusp (Figure17C). When observing natural dentition, thiscusp will often exhibit a greater degree ofwear when compared to the mesiolingualcusp.

The mesiolingual cusp is most influenced bythe lateral movement; hence colour codedblue (Figure 18A and B). This cusp is largerin size and the triangular ridge is larger andhigher in the occlusal table when comparedwith the distolingual cusp (Figure 18C).


Figure 14. A and B, Distolingual cusp of the upper molar.

Figure 15. A and B, Development of the cusp morphology of the lower molar.

Figure 16. Mesial buccal cusp positioned so that it contacts the mesial marginal ridge of the upper molar.

Figure 17. A–C, Distolingual cusp of the lower molar.

A B C

A B

A B


OCCLUSAL FUNCTION AND THE SINGLE CROWN

This completes the lingual shear cusps of thelower molar: note the similarities with thebuccal shear cusps of the upper molar (Figure19).

The middle buccal cusp of the lower firstmolar is influenced by the mediotrusivemovement and is assigned the colour green(Figure 20A and B). Given the large size ofthis cusp and the mesiolingual cusp of theupper molar care must be taken to allow forsufficient room for the mediotrusivemovement. The movement follows thedistobuccal disectional groove. The height ofcontour of the triangular ridge is towards themesial side of the cusp (Figure 20C). In thisocclusal scheme there is a small auxiliaryridge running to the mesial. This produces a

relatively simple form for this large cusp.The mesiobuccal cusp is not significantlyinfluenced by the mediotrusive movement asthe only cusp that would affect it is the lingualcusp of the upper second premolar (not alarge cusp). This cusp can be developedalmost like the buccal cusp of the secondlower premolar with the cusp tip occludingon the opposing marginal ridge.

The distobuccal cusp is like the upperdistolingual cusp; small and rarely having anocclusal contact. If not for the disectionalgroove, it could be considered an extensionof the middle buccal cusp (Figure 21).

This completes the forming of the buccalstamp cusps and the occlusal form of the

Figure 18. A–C, Mesiolingual cusp of the lower molar.

Figure 19. Lingual shear cusps of the lower molarshare similarities with the buccal shear cusps ofthe upper molar.

Figure 20. A–C, Middle buccal cusp of the lower molar.

Figure 21. A and B, Distobuccal cusp of the lower molar. Figure 22. Lower molars: indirect restoration (crown)on the 36, a direct restoration on the 37, and anatural tooth on the 38.

A B

A B C

A B C

ROTSAERT

lower molar. The development of the occlusalmorphology using this method shouldgenerate a form that is without excursivecontacts and blends with the adjacentdentition.

ConclusionThe most restored teeth are the molars, so asa technician it is important to be able tofabricate molar restorations that arefunctionally correct. The occlusal compass isa powerful tool that we can use to develop theocclusal morphology. Whenever we see anocclusal surface that has a large cuspcontacting somewhere within that tooth’socclusal table, the occlusal compass will helpguide us in the development of cusppositions and forms. In restoring theposterior anatomy the adage form followsfunction is of paramount importance. Bydeveloping the occlusal forms one cusp at atime with the occlusal compass in mind weare able to recreate natural anatomic formsthat will function in harmony with thepatient’s occlusal determinants. The carefulobservation of the wear pattern of the teethadjacent to the tooth being restored gives usan idea of the excursive pathways for eachpatient. These wear facets are a guide to theangles and direction of the patient’s habitualmovements that we then us to individualizethe occlusal compass.

In the example of the lower molar we have anindirect restoration (crown) on the 36, adirect restoration on the 37. and a naturaltooth on the 38. We have used the waxingscheme and the occlusal compass to attemptto replicate the natural morphology found inthe 38 in the 36 crown (Figure 22).

The replication of nature in form andfunction is an ideal worth striving for. Theconcepts outlined here using wax can beapplied to all restorative materials includingamalgam, composite, gold, and porcelain.

ConflictsNone declared.

BibliographyDe Vreugd RT. The Occlusal compassconcept: A practical approach to posteriormorphology. Available at:http://idseminars.com/articles/QDT_Article_1997.pdf.

Douglass GD, De Vreugd RT. The dynamicsof occlusal relationships. In: McNeill C (ed).Science and Practice of Occlusion. Chicago:Quintessence; 1997.

Polz MH. Inlay-und Onlay Teckniken.Dental-Labour, Documentation 2. Munich:Verlag Neuer Merkur; 1987.

Slavicek R. The Masticatory Organ. AnnArbor: Needham Press; 2003.


OCCLUSION

Apractical approach to dental care involvesconceptualizing the final result or, in other

words, having a game plan. One way toapproach the patient’s stomatognathic systemis to conceptualize the final occlusalrelationship between the maxillary andmandibular arches. A recommended approachis the 10 essential steps for occlusal evaluation(Table 1).

Table 1. 10 Essential Steps for OcclusalEvaluation

1. Chief Concern2. Facially Generated Treatment Planning3. “Thinking Wax”4. “CR”/ Vertical Dimension5. Sagittal 1st6. Coronal 2nd7. Occlusal Plane8. Tooth Anatomy9. Materials10. Maintenance/Orthotics

1. Chief ConcernPatients attend dental practices for manyreasons with various expectations including achief concern. An important consideration forthe dental team to appreciate is what could gowrong post treatment with the patient’s chiefconcern and why? Distilled down, the answerfalls into three main areas: diet, hygiene, andparafunction.1 All three of these etiologies arepatient preventable only. The dental teamtherefore act as the facilitators of dentaleducation and patient oral care. That is whyexcellent communication and rapport areessential before embarking on treatment. Anon-compliant patient will doom the dentalteam’s efforts.

A patient that refuses to participate in effectivepersonal and professional oral hygiene care willundoubtedly have future problems orcompromises with their oral health such asroot caries, periodontal issues, and esthetics(e.g., staining) to mention a few. Diet isanother source for failure; specifically, sweets

intake. Patients need to be educated on therelationship between sweets and caries and thesignificance of the frequency and volume ofconsumption. The patient also needs toappreciate that sweets are more than justchocolate and candies. There are many sourcesof sugars that the patient might not realize thatare damaging such as fruits or sports beverages(sweet/food breakdown product “acid” attacksor acidic substances).2 Age and the associateddecline in salivary flow also requireexplanation. Strategies to offset lifestyledecisions can then be formulated.

The third and most significant reason for post-treatment failure is parafunction, betterdescribed as bruxism.3 Patients’ teeth are nevertogether unless they are chewing orswallowing.4 Patients teeth might touch for asplit second when they chew or they mighttouch when they swallow. The dental teammust educate patients to keep their teeth apart.For patients that brux at night or who justwant to protect their dentition while they sleep,


Dental Occlusion Evaluation: 10 Essential StepsÉvaluation de l’occlusion : 10 étapes essentielles

By Dr. Michael Racich

About the Author

Dr. Racich is a 1982 graduate from University of British Columbia with a general practice in downtownVancouver emphasizing comprehensive restorative dentistry, prosthodontics and TMD/ orofacial pain. Dr.Racich is a member of many professional organizations including the Canadian Academy of RestorativeDentistry and Prosthodontics, the Pacific Coast Society for Prosthodontics, and the International Associa-tion for the Study of Pain. He is a Fellow of the Academy of General Dentistry, the International Congressof Oral Implantologists, and the American College of Dentists as well as a Diplomate, American Board ofOrofacial Pain. Dr. Racich has published in peer-reviewed scientific journals such as the Journal of Pros-thetic Dentistry and the Canadian Dental Journal and lectured nationally and internationally on subjectsrelating to patient comfort, function and appearance. He currently mentors the didactic/clinical F.O.C.U.S.(Fundamentals Of Creating a Uniform Stomatognathic system) study clubs in British Columbia.

ABSTRACTA frequently asked question by dental practitioners is: “What are the essentials for assessing a patient’s occlusion?” There are manyschools of thought when addressing this question but when one distils down the various philosophies there are a few fundamentalconsiderations that emerge. The following brief essay will lay out 10 basic steps for dental occlusal evaluation.

RÉSUMÉUne question souvent posée dans la pratique dentaire est la suivante : « Qu’est-ce qui est important de vérifier lors de l’évaluation del’occlusion d’un patient? ». Il existe plusieurs écoles de pensée à ce sujet mais lorsqu’on examine de près les diverses philosophies, onconstate qu’il y a quelques aspects fondamentaux à considérer. Le bref compte rendu suivant vous révèlera les 10 étapes essentielles àl’évaluation de l’occlusion.

RACICH

fabrication of a full coverage hard acrylicmaxillary or mandibular orthotic isaccomplished.

Diet, hygiene, and bruxism. Make all patientsaware of these three vices. Failure to properlyeducate and monitor these three etiologiesmakes for post-treatment untoward sequelae.

2. Facially Generated Treatment PlanningHaving a systematic, thorough approach todiagnostic planning that intimately involvespatient input is critical. Facially generatedtreatment planning helps co-ordinate thedental team and patient objectives as “wemeet the person, then the face, the mouth,and finally the teeth.”5–8

Facially generated treatment planning beginsafter the dental team has met the patient(objectives, expectations, bias, etc., realized)and then they thoroughly assess the face. Theface is assessed both from the lateral (sagittal)viewpoint as well as the frontal (coronal).Basic common sense applies as the dentalteam gauges the lateral view for Angleclassification and for any soft tissueabnormalities (e.g., nose profile). Lateralcephalometric analysis can be useful at this

point to locate hard tissue (e.g., the teeth)landmarks as well as soft tissue (e.g., theesthetic plane) landmarks.9 From the frontalperspective we can assess facial proportion,the so called rule of thirds, for evennessbetween the upper, middle, and lower face(Figure 1).10

Meeting the mouth the dental team assessestooth display at rest (repose) as well as in fullsmile.11 The dental team can next assesswhether or not the arch form is too narrowrelative to the face and anterior toothposition. The rule of opposites can beapplied. The rule of opposites suggests that ifsomething is narrow (the face for example)then subtly widening an associated feature (inthis case the arch form) will let the faceappear wider and the anterior teeth smaller(Figure 2).

Evaluation of occlusal plane form (generallyit should “appear” parallel to the horizon)and overall intra and inter-tooth proportionsis also spied. Direct mock-ups with eithernon-adhesively bonded composite or whiteperiphery tray wax while utilizing a black feltmarking pen for block outs yield real-timevirtual evaluation which can then betransferred appropriately for in-office or

laboratory assessment (Figure 3).

Lastly, the teeth and their structural integrityare scrutinized utilizing basic restorative andoperative dental diagnostic criteria. Theperiodontal status must also not be neglected.

3. “Thinking Wax”When single tooth dentistry is practiced, theprocess is visualized by the practitioner.Removal of pre-existing restorations andcaries, cavity preparation and toothfoundation design, restorative material choiceand placement, finalization of the project areall in the operators mind before the hand-piece is picked up. The more thorough theconceptualization of the final result the finerthe outcome and the smoother the sequenceof treatment runs; relatively simpleprocedures such as these happensubconsciously and is effortless. This is notthe case with more complex undertakings. Apractitioner, especially in the formative years,is being extremely foolish if they believe theycan take on complex rehabilitative effortswithout having a clear, concise idea of the endresult. In their minds eye the practitionermust have the final design concept mastered.One excellent method of facilitating thisconceptualization process is “thinkingwax.”12 Thinking wax is the process wherebythe practitioner goes through theconceptualization exercise with complete waxdentures in mind. The “thinking wax” goalis to therefore answer the question: “Whatwould be done for this patient if completedentures were being fabricated given thepresent circumstances?” Depending on theskeletal jaw relationships and facialproportions, soft tissue contours, arch andtooth size considerations, or patient’s desiresand expectations would it not be nice to be


Figure 1. The Rule of Thirds showing wellproportioned facial featuresImaged reprinted with permission from Racich MJ.The Basic Rules of Oral Rehabilitation.

Figure 2. Narrow buccal corridor and longish frontteeth offset an oval face.Imaged reprinted with permission from Racich MJ.The Basic Rules of Oral Rehabilitation.

Figure 3. Direct mock-ups utilizing wax and blackfelt pen allow the patient to quickly visualizeesthetic or cosmetic changes to their dentition.Imaged reprinted with permission from Racich MJ.The Basic Rules of Oral Rehabilitation.


DENTAL OCCLUSION EVALUATION: 10 ESSENTIAL STEPS

able to be able to move the teeth and bone toa conceptualized relationship just like whichcan easily be done with wax denture set-ups?Along with other record taking efforts, suchas charting, radiographs, and mounted studycasts, diagnostic wax-ups can be producedwhich can be further utilized to consult withpatients or other interdisciplinary teammembers.

When conceptualizing the final result or“thinking wax” an overall concept such as amutually protected occlusal scheme shouldbe ascertained (Figures 4 and 5).3,13

Ideally all the posterior teeth should contactevenly and down their long axes.14 The moreposterior teeth that are in even contact themore that any clenching forces can bedistributed. Anterior teeth should touchminimally if at all when the arches aretogether.4 Williamson and others have alsoshown that if the anterior teeth are in contactduring excursions then less force is in themasticatory system (due primarily to elevatormuscle relaxation).15,16 The anterior teeth arealso at a better mechanical advantage towithstand lateral forces due the class III leverprinciples involved.

Thus, ideally during clenching activities theposterior teeth are “protecting” the anteriorteeth and during parafunctional activitiessuch as bruxing the anterior teeth are“protecting” the posterior teeth from anyexcessive lateral forces. Nature has set-upquite an efficient machine by making theposterior teeth not only the chewing workhorses but also the intermaxillaryrelationship stabilizers while allowing theanterior teeth to be the food knives andposterior stabilizer protectors.

4. Centric Relation/Vertical DimensionExtensive restorative dental/ prosthetic workrequires a starting point. Traditionally, thishas been centric relation (CR).3 A look at theGlossary of Prosthodontic Terms, however,shows seven different definitions. CR thusbecomes the Confusing Relation.Furthermore, some clinicians advocate otherstarting positions such as MyoCentric.17 Thisonly leads us to more Confusion. What then,is the practitioner to do? Who is right? Whois wrong? The truth is that it is not so muchwhat the starting point is but howreproducible and stable the starting positionis.18 CR, therefore, is a ConsistentlyReproducible position.

The health of the temporomandibular joint(TMJ) must be delineated early in treatmentplanning. Lack of inflammation anddiscomfort must be present and can bereadily verified by examination and tests suchas joint loading, functional resistance, andpalpation.19 Although TMJ noises (e.g.,clicking in disc displacement with reduction)can be troublesome for patients, in theabsence of pain and dysfunction thepractitioner can accept this situation as stablesince the TMJ tissues have the capacity for

remodelling and repair.20 Once again, this canbe evaluated (joint loading, functionalresistance testing, palpation). Treatment withthe condylar head in the glenoid fossa with(“adapted centric relation”21) or without TMJnoises is not only practical but alsophysiologic.4 When the opposing dentitionsocclude in CR we have centric occlusion(CO) (which may or may not coincide withmaximum intercuspation or habit bite).3

Most importantly, Consistency andReproducibility of this position is desirablewhen extensive treatment has beenperformed for long-term maintenancefacilitation.

Occasionally it is necessary to rehabilitatewith the condyles in a relatively forwardposition in the glenoid fossa. This can occurin such situations as when the retrodiscaltissues cannot withstand loading, thepractitioner wants to treat “on the disc”, orperhaps the patient is a skeletal class II andwants their final occlusal treatment positionto be brought forward (a class II that wantsto be a class I).22 Some practitioners actuallyfavour this relationship, especially those inthe MyoCentric camp.17 The main issue hereis not whether this is bad or good or who’sright or wrong but instead how consistentlyreproducible and stable is the relationship ofthe TMJs, especially when the teeth occlude.18

Another consideration when analyzing thestarting position or “CR” is to take intoaccount vertical dimension. Occlusal verticaldimension is defined as: “the distancemeasured between two points when theoccluding members are in contact” while therest vertical dimension is: “the distancebetween two selected points measured whenthe mandible is in the physiologic restposition.” The vertical dimension of speechis: “that distance measured between twoselected points when the occluding membersare in their closest proximity during speech.”3

It is important to note that the maximumvertical dimension that is physiologicallyacceptable is the latter, i.e., speech determinesthe maximum permissible.10 Therefore, withthe aid of facially generated treatmentplanning and conceptualizing the final result(thinking wax) guesstimation of the occlusalvertical dimension can be made at aconsistently reproducible position (CR) thatthe practitioner can work with (Figure 6).

Figures 4 and 5. Mutually protected occlusion.Posterior teeth protect anterior teeth inmaximum intercuspation while anterior teethprotect posterior teeth in excursive functioning.Imaged reprinted with permission from RacichMJ. The Basic Rules of Oral Rehabilitation.

Figure 6. CR and CO. The teeth occlude when theTMJs are in a Consistently Reproducible positionwhere the condyles are in the anterior superioraspect of the glenoid fossa at an acceptableocclusal vertical dimension.Imaged reprinted with permission from RacichMJ. The Basic Rules of Oral Rehabilitation.

RACICH

5. Sagittal 1stThe Glossary of Prosthodontic Terms definessagittal as: “situated in the plane of the cranialsagittal suture or parallel to that plane” andthe sagittal plane as: “any vertical plane …that divides a body into right and leftportions.”3 Knowing where the maxillary andmandibular central incisors are in the sagittalplane allows the practitioner to optimizepatient function.23–25 The envelope offunction (“the three-dimensional spacecontained within the envelope of motion thatdefines mandibular movement duringmasticatory function and/ or phonation”3) isrespected.26 Undesirable tooth contacts such

as anterior fremitus (“… a vibration palpablewhen the teeth come into contact”3) can beeliminated (Figure 7).

6. Coronal 2ndCoronal 2nd is better known as Smile Design101 or Smile Design Du Jour. Setting orconceptualizing where the anterior teeth needto be positioned facially really is no moredifficult than doing a wax denture try in(thinking wax)!27–29 The interesting article byWaliszewski et al.30 substantiates thesecontentions nicely. The authors created threedifferent denture set-ups for six differentpatients and asked a group of people whichthey preferred. Did they prefer the naturallook, the supernormal look, or the denturelook (Figures 8–10)? The results showed that55% preferred the natural look while 26%preferred the denture look! Surprisingly, only19% favoured the supernormal look which isso prevalent in today’s Western World. SmileDesign Du Jour is truly in the eyes of thebeholder.

7. Occlusal PlaneThe occlusal plane is defined by the Glossaryof Prosthodontic Terms as “the average planeestablished by the incisal and occlusalsurfaces of the teeth. Generally, it is not aplane but represents the planar mean of thecurvature of these surfaces.”3 Themandibular occlusal plane usually can bevisualized when the mandible is at rest as arelatively flat plane with the posterior buccal

cusp tips and the incisal edges parallel to thehorizon. The occlusal plane anatomicallyruns from approximately half way up theretromolar pad to slightly below thecommisures of the lips. This can be verifiedwith cephalometrics.31 The maxillary occlusalplane similarly parallels the horizon with theposterior buccal cusp tips co-incident andnot canted. If the practitioner so chooses, fora patient with a pleasing smile this can bereadily confirmed by placing a maxillary caston a bench top. The buccal cusps bilaterallyshould touch the surface evenly (with theincisal third of the maxillary central incisorsperpendicular to the horizon).32 Patientsobviously do not want to walk about post-treatment with sloped dentitions when theysmile or speak.

8. Tooth AnatomyWhen dentistry is practiced that recreatesnatures design, then esthetic and functionalresults are achieved. Tooth anatomyrestoration is thus an integral part of occlusalrehabilitation or stabilization for mastery ofthe stomatognathic system.

To refresh the practitioner’s memories abouttooth anatomy there are many excellenttextbooks available.33,34 Not only do thesetextbooks provide superb diagrams, the morerecent publications have graphic programsthat can be loaded onto computers. Toothimages can be rotated, teeth sectioned, andocclusal inter-relationships evaluated. Teeth


Figure 7. Excessive anterior tooth contact canresult in tooth, periodontal, and restorative/prosthodontic trauma.Imaged reprinted with permission from RacichMJ. The Basic Rules of Oral Rehabilitation.

Figure 8. Natural look. Image courtesy Dr. MichaelWaliszewski.

Figure 9. Supernormal look. Image courtesy Dr.Michael Waliszewski.

Figure 10. Denture look. Image courtesy Dr.Michael Waliszewski.


DENTAL OCCLUSION EVALUATION: 10 ESSENTIAL STEPS

have many planes, angles, grooves, tips, and

fossa. Sharp cusp tips into well constructedfossa facilitate occlusal equilibration whilediffering facial planes on a maxillary centralincisor diffuse and reflect light to entertainthe observer’s eyes (Figures 11 and 12).

There are some basic, distilled down rules tofollow with tooth anatomy and inter-toothrelationships35:1. Facial and lingual contour

a. height of contour on the facial and lingual of all in the gingival third except on the lingual of mandibular bicuspids and molars where it is the middle third.

b. height of contour extends from the cementoenamel junction (CEJ) on the facial and lingual of all teeth except on the lingual of mandibular bicuspids andmolars where it may extend 1 to 1.5 mmabove the CEJ.

2. Proximal contact areasa. are in the occlusal (incisal) third of all

teeth except between the maxillary molarcontacts where it is at the junction of theocclusal and middle third.

b. viewed from the occlusal/ incisal the proximal contacts always are facial to thecentral fossa except between Mx molar tomolar contacts where it is on the centralfossa line.

3. Proximal surface from the contact area facial-lingually and occlusal/ incisal-cervically is flat or slightly convex.

4. Marginal ridges are at the same height regardless of the presence or absence of occlusal contact.

5. Curve of Wilsona. mandibular premolar buccal cusps are

higher than lingual cusps by up to 1–1.5 mm.

b. maxillary molar buccal cusps are shorterthan lingual cusps by up to 1–1.5 mm.

6. There are four embrasures:a. occlusal/ incisal, gingival, lingual, facialb. with the lingual > facial and the gingival

> occlusal/incisal

9. MaterialsDental materials are continuously beingintroduced into the marketplace and henceto the dental practitioner. The whole issue ofchange at first appears daunting. However,approached in an evidenced-based mannerit’s not as difficult as it appears at first glanceespecially if we treat patients similar to whatthe dental team would like to be treated like,i.e. not experimental specimens. Evidence-based dentistry involves that rich blend ofpatient values, practitioner expertise and bias,and what the reported literature has to sayabout a device, technique or product (Figure13).36

When new techniques or materials areintroduced, a go low, go slow approach ispractical. Practitioners might wish to try

different products but might also want to doso under as controlled an environment aspossible such as taking hands-on continuingeducation programs (where products can beused in real time [i.e., intraorally]) or byselectively incorporating a technique orproduct in a routine, low risk situation wherethere is a high probability of successregardless what is employed (e.g., a newdental cement for a well designed castcrown). Also, conferring with peers withregards to their experiences is another usefultool. The practitioner can then distil andevaluate relative to personal experiences andbiases and the specific clientele that seeks thedental team’s services. Ultimately, as long asthe dental materials are appropriately selectedfor the right dental environment, i.e., thepatient’s milieu (their occlusal scheme andlong-term commitment/ownership), thenprognosis can be reasonably stated.

10. Maintenance/ OrthoticsUpfront business practices and cooperativewell delineated patient relationships allowlong-term work warranties andmaintenance.37,38 Occlusal observations atrecare hygiene appointments, for example,can be routinely done.39 Reinforcement ofnocturnal occlusal protection in the form ofdental orthotics can also be exercised.40 Thereare many uses for dental orthotics with themost practical being simple, straight-forwardocclusal protection and hence, occlusionstabilization (Table 2).41,42

Table 2. Considerations for Dental Orthoticusage:1. Vertical dimension changes2. Occlusion optimization3. Occlusal protection4. TMJ unloading5. Mandibular repositioning6. Influence growth7. Altered sensory input8. Cognitive awareness9. Placebo10. Expectations11. Regression to the mean

Concluding Remarks and Recommen-dations1. Patient expectations (knowledge of),

education and long-term commitment requisite.

2. Conceptualization of end product is

Figures 11 and 12. Cusps, fossas, tooth planes arenot only function but highly esthetic.Imaged reprinted with permission from RacichMJ. The Basic Rules of Oral Rehabilitation.

Figure 13. Evidence-based dentistry. The greenzone represents the ideal synergistic result whenthe evidence, clinician bias, and patient values arerespected.Imaged reprinted with permission from RacichMJ. The Basic Rules of Oral Rehabilitation.

RACICH

prudent before treatment initiation. 3. A sequential, consistent treatment

approach is advised.4. Optimization of oral anatomy and

physiology routinely should be strived for.

5. An evidence-based approach to restorative and prosthodontic materials is today’s standard of care.

6. Ongoing maintenance care is always facilitated.


References1. Racich MJ. The basic rules of oral

rehabilitation. Markham, ON: Palmeri Publishing; 2010, 13–15.

2. Lussi A, Hellwig E, Zero D, Jaeggi T. Erosive tooth wear: diagnosis, risk factorsand prevention. Am J Dent 2006;19:319–25.

3. The glossary of prosthodontic terms. J Prosthet Dent 2005;94:1–92.

4. Lundeen H, Gibbs C. Jaw movements andforces during chewing and swallowing and their clinical significance. In: Advances in occlusion. Boston: John Wright PSG; 1982, 2–32.

5. Aucoin K. Face forward. Boston: Little, Brown & Co.; 2000.

6. Mack MR. Perspective of facial esthetics in dental treatment planning. J Prosthet Dent 1996;75:169–76.

7. Rifkin R. Facial analysis: a comprehensiveapproach to treatment planning in aesthetic dentistry. Pract Periodontics Aesthet Dent 2000;12:865–71.

8. Romano R. ed. Art of the smile. Chicago:Quintessence; 2005.

9. Bergman RT. Cephalometric soft tissue facial analysis. Am J Orthod DentofacialOrthop 1999;116:373–89.

10. Mack MR. Vertical dimension: a dynamicconcept based on facial form and oropharyngeal function. J Prosthet Dent1991;66:478–85.

11. Hasanreisoglu U, Berksun S, Aras K, Arslan I. An analysis of maxillary anteriorteeth: facial and dental proportions. J Prosthet Dent 2005;94:530–8.

12. Racich MJ. The basic rules of oral rehabilitation. Markham, ON: Palmeri Publishing: 2010; 80–2.

13. Lundeen HC, Gibbs CH. The function of

teeth. L and G Publishers LLC; 2005.14. Schuyler CH. The function and

importance of incisal guidance in oral rehabilitation. 1963. J Prosthet Dent 2001;86:219–32.

15. MacDonald JW, Hannam AG. Relationship between occlusal contacts and jaw-closing muscle activity during tooth clenching: part I. J Prosthet Dent 1984;52:718–28.

16. Williamson EH, Lundquist DO. Anteriorguidance: its effect on electromyographicactivity of the temporalis and masseter muscles. J Prosthet Dent 1983;49:816–23.

17. Jankelson B. Neuromuscular aspects of occlusion: effects of occlusal position onthe physiology and dysfunction of the mandibular musculature. Dent Clin N Amer 1979;23:157–68.

18. Racich MJ. Oral rehabilitation for the asymptomatic patient: what starting position should I choose? J Can Dent Assoc 2003;69:457–8.

19. Okeson JP. Management of temporomandibular disorders and occlusion. 5th ed. St. Louis: Elsevier; 2002, 111,151–9.

20. Eriksson L, Westesson PL. Condylar anddisk movements in fissected TMJ sutopsydpecimens. University of Lund, 1985.

21. Dawson PE. Functional occlusion: fromTMJ to smile design. St. Louis: Mosby; 2007.

22. Simmons HC, Gibbs SJ. Initial TMJ diskrecapture with anterior repositioning appliances and relation to dental history.J Craniomandib Pract 1997;15:281–95.

23. Thuer U, Grunder J, Ingervall B. Pressurefrom the lips on the teeth during speech.Angle Orthod 1999;69:133–40.

24. Runte C, Lawerino M, Dirksen D, Bollmann F, Lamprecht-Dinnesen A, Seifert E. The influence of maxillary central incisor position in complete dentures on /s/ sound production. J Prosthet Dent 2001;85:485–95.

25. Runte C, Tawana D, Dirksen D, Runte B,Lamprecht-Dinnesen A, Bollmann F, Seifert E, Danesh G. Spectral analysis of /s/ sound with changing angulation of the maxillary central incisors. Int J Prosthodont 2002;15(3):254–8.

26. Posselt U. Studies on the mobility of thehuman mandible. Acta Odontol Scand 1952;10(suppl):1–160.

27. Chiche GJ, Aoshima. Smile design: a

guide for the clinician, ceramist, and patient. Chicago: Quintessence; 2004.

28. Parekh S, Fields HW, Beck FM, Rosenstiel SF. The acceptability of variations in smile arc and buccal corridor space. Orthod Craniofac Res. 2007;10:15–21.

29. Golub-Evans J. Unity and variety: essential ingredients of a smile design. Curr Opin Cosmet Dent 1994;2:1–5.

30. Waliszewski M, Shor A, Brudvik J, Raigrodski AS. A survey of edentulous preference among different denture esthetic concepts. J Esthet Restor Dent 2006;18:352–69.

31. Grummons D, Ricketts RM. Frontal cephalometrics: practical applications, part 2. World J Orthod 2004;5:99–119.

32. Keough B. Occlusion-based treatment planning for complex dental restorations:part 2. Int J Periodontics Restorative Dent2003;23:325–35.

33. Scheid RC. Woelfel’s dental anatomy: itsrelevance to dentistry. 7th ed. Baltimore:Lippincott Williams & Wilkins; 2007.

34. Ash MM, Nelson SJ. Wheeler’s dental anatomy, physiology, and occlusion. 9th ed. Philadelphia: Saunders; 2009.

35. Racich MJ. The basic rules of oral rehabilitation. Markham, ON: Palmeri Publishing; 2010, 119.

36. Sackett DL, Rosenberg WM, Gray JA, etal. Evidence-based medicine: what it is and what it isn’t. Brit Med J 1996;312:71–2.

37. McKenzie S. Provide a service ... then getpaid. J Indiana Dent Assoc 2001;80:16–17.

38. Wasoski RL. Stress, professional burnoutand dentistry. J Okla Dent Assoc 1995;86:28–30.

39. Gray HS. Occlusion and restorative dentistry. N Z Dent J 1993;89:61–5.

40. Klineberg I. Occlusal splints: A critical assessment of their use in prosthodontics.Aust Dent J 1983;28:1–8.

41. Dao TT, Lavigne GJ. Oral Splints: The crutches for temporomandibular disorders and bruxism? Crit Rev Oral Biol Med 1998;9:345–61.

42. Racich MJ. Predictable fabrication and delivery technique for full-coverage hardacrylic non-sleep-apnea dental orthotics.J Can Dent Assoc 2006;72:233–6.



OCCLUSION

Anterior Guidance: What Does It Mean To You?Guidance antérieure : Qu’est-ce que cela signifie pour vous?

By Dr. Kim Parlett, DDS, MSc

About the Author

Dr. Kim Parlett, DDS, MSc, is in private practice in Bracebridge, Ontario

ABSTRACTAnterior guidance is thought to be well understood by most dentists; however, a distilling process has reduced our current practice toa rather mechanistic approach to therapy which lacks understanding and rationale. The author reviews what we know about anteriorguidance and what we may have forgotten and provides evidence for a more individualized treatment concept when altering ante-rior guidance through our therapies.

Three basis occlusion philosophies have dominated dental teaching and research for the past decade: bilateral balanced occlusion,group function occlusion, and canine or mutually protected occlusion. Each therapeutic approach has its own applications but noneis appropriate for every patient. The individuality of each therapy must be understood. Through careful review of the literature werecognize several advantages to designing therapies that favour canine protected occlusions. This type of occlusion has several ad-vantages over the other concepts. First, masticatory muscle activity is reduced with this guidance system as opposed to group or bi-lateral balance; second, lateral forces directed off the long axis of teeth from parafunction are reduced; and third a mechanicaladvantage of a class 3 lever is imparted to the stomatognathic system.

Anterior guidance is misleading because it suggests that all anterior teeth have a disclusive function. The anterior teeth are consid-ered a functional unit but the central incisors are not part of any laterotrusive control. They are dominant in proprioception for deter-mining the frontal area of the masticatory cycle and speech. Lateral incisors are highly variable in position and are more dominantduring mixed dentition through maturation. The relationship of the cuspid and bicuspid is poorly understood by a static dental clas-sification. It is a dynamic relationship where control of immediate protrusive disocclusion can be affected. The ultimate goal of all oc-clusal schemes and therapy should be to provide primary stability in maximum intercuspation and disocclusion of all posterior teethin incursive and excursive function and parafunction. This disocclusion of posterior teeth is highly dependent on the relationship ofanterior guidance and posterior condylar guidance. This relationship has been well documented in the literature but it has also beenshown that it is highly individualized. Measuring functional condylar movements can help us to set the other parameters of anteriorguidance, occlusal plane and cusp inclination to create an efficient chewing apparatus that minimizes destructive forces on our den-tal restorations.

RÉSUMÉLa plupart des dentistes pensent bien comprendre la guidance antérieure; toutefois, par un processus d’épuration, notre pratiquecourante s’est vue transformer en une méthode thérapeutique plutôt mécaniste qui manque de compréhension et de justification.L’auteur passe en revue ce que nous connaissons déjà au sujet de la guidance antérieure et ce que nous avons peut-être oublié etmontre un concept thérapeutique plus individualisé lorsqu’il s’agit de modifier la guidance sur les dents antérieures.Trois philosophies de base sur l’occlusion ont dominé l’enseignement et la recherche en médecinet dentaire depuis les dix dernièresannées : occlusion bilatéralement équilibrée, occlusion unilatéralement équilibrée (fonction de groupe) et occlusion mutuellementprotégée (fonction canine). Chaque méthode thérapeutique possède ses propres applications, mais aucune ne convient à chaque patient.Il faut bien comprendre le caractère individuel de chaque traitement. Après un examen minutieux de la documentation, nousreconnaissons plusieurs avantages de concevoir des traitements qui favorisent la fonction canine. Ce type d’occlusion comporte plusieurs

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avantages par rapport aux autres concepts. Premièrement, l’activité des muscles masticatoires est réduite avec la guidance parrapport à l’équilibration occlusale bilatérale ou à la fonction de groupe; deuxièmement, les forces latérales dirigées du grand axedes dents de la parafonction sont réduites; troisièmement, un avantage mécanique d’un levier de classe 3 est concédé au systèmestomatognatique.

La guidance antérieure peut induire en erreur car elle suggère que toutes les dents antérieures ont une déviation. Les dentsantérieures sont considérées une unité fonctionnelle mais les incisives centrales ne font pas partie du contrôle du mouvementlatéral de la mandibule. Elles sont dominantes à la proprioception pour déterminer la partie frontale du cycle masticatoire et del’élocution. La position des incisives latérales est très variable et ces dernières sont plus dominantes au stade de la dentition mixtejusqu’à la dentition permanente. On comprend mal la relation entre la canine et la prémolaire selon une classification dentairestatique. Il s’agit d’une relation dynamique dans le cas où le contrôle de la déviation avec problème protrusif peut être affecté. Lebut ultime de tous les systèmes occlusaux et du traitement doit être de permettre la stabilité primaire d’intercuspidation maximale,le rétablissement de l’occlusion de toutes les dents postérieures et la correction des parafonctions. Le rétablissement de l’occlusion des dents postérieures est fonction de la relation de la guidance antérieure et de la guidancepostérieure condylienne. Cette relation a été bien documentée, mais il a été démontré aussi qu’elle est très individualisée. La mesuredes mouvements fonctionnels du condyle peut nous aider à définir les autres paramètres de la guidance antérieure, le plan occlusalet l’inclinaison des cuspides pour créer un appareil de mastication efficace qui réduit les forces destructrices sur les restaurationsdentaires.


“Anterior guidance” is a term that is instantlyrecognizable to most dentists. It is a term weheard repeatedly through dental school andone that is referenced, in one way or another,in every lecture since then. It is inherentlyunderstood by all dental specialties and isvoid of the ambiguity and confusion thatcomes from a term such as “centric relation”which has seven current definitions in theGlossary of Prosthodontic Terms. So, what doesthe term anterior guidance mean to you? It ismy hope that this article will in some wayhelp our readers to understand and utilizetheir own therapeutic, anterior guidanceconcept.

From my personal observations over the pastdecade there appears to have been a declinein our profession’s interest in the details ofocclusal study. With this has come a rathermechanistic approach to anterior guidancewhich includes duplication of existing lingualcontacts and contours using custom incisalguide tables (Figure 1), trial and errormethodology with “in the mouth”equilibration of temporary crowns andarbitrary settings for adjustable incisal guidetables that reference standardized norms, andmy personal favourite, “let the laboratorytechnician work it out!”

What happened to the science? Major M. Ash,Head and Face Medicine 2007;3:1 wrote thatthe paradigm shift to evidence baseddentistry (EBD) that relates to occlusaltherapy (OT), selective occlusal adjustment

(OA), and stabilization splint (SS) therapy forTMDs has had an unfavourable impact onthe teaching of many of the importantaspects of occlusion needed in daily dentalpractice. The teaching of occlusion haspractically been abandoned in our dentalschools because of EBD inducedcontraindications for OA and SS. He arguesthat it is important to bring a clinical realityback into the dental curriculum bysystematically teaching all aspects of occlusalmanagement. This article will review what wedo know about anterior guidance offeringevidence-based research to support it. Thereis some evidence to suggest a more scientificapproach will allow us to treat our patients toa more individualized, functionally efficientoutcome. The important questions we needto review when considering anteriorguidance is: What therapeutic concept is rightfor our patient? Does anterior guidanceprovide any benefits to the stomatognathicsystem? What teeth are involved in lateral andprotrusive guiding movements? Whichsurfaces of teeth are involved? How steepshould the anterior guidance be? How muchanterior guidance is too much? What is ourtherapeutic concept when we have noanterior guidance, (class 2, div.1, and class3s)? (Note: Review of the literature suggeststhat the distribution of skeletal classificationfor the current North American andEuropean populations is skeletal class 1:37.2%; skeletal class 2: 57.2%, and skeletalclass 3: 11.0%)

Figure 1A. Sam Articulator with adjustable incisalguide table. 1B. Gerbach programmed incisalguide table for sequential wax-up teeth #3-6. 1C.custom incisal guide table from patients existinganterior guidance contours.

A

B

C


ANTERIOR GUIDANCE: WHAT DOES IT MEAN TO YOU?

First let us clear up the semantics. Caninedominant occlusion does not equal canineprotected occlusion (Figure 2). Canineprotected occlusion is a therapeutic concept!Canine dominance is an evolutionaryphenomena consistent from the great apes tomodern man. With brain lateralization,development of speech and posturaluprighting the canine has regressed into thedental arches. Nevertheless the function ofcutting and tearing food has remainedprimarily the same for more than 3 millionyears!1–2

There have been three therapeutic guidanceconcepts developed since the late 1800s.These theorems were developed by theleaders in dentistry of the time and becamethe object of great occlusion debate anddivision through the 1900s. The threeconcepts were (1) bilateral balancedocclusion, (2) group function occlusion, and(3) canine protected occlusion (also knownas mutually protective occlusion) (Figure 3).

All three philosophies were developed astherapeutic concepts to aid the practitionerwith his/her treatment goal. Thisphilosophical debate continued to divideorganized dentistry into the late ’70s. Theproponents of each occlusion concept havingan uncompromising belief that theirparticular concept could be applied to allpatients whether dentate or fully edentulous!

Today, there is widespread general agreementthat anterior guidance is a good thing toprovide in our therapies. It means posterior

teeth don’t touch during incursive orexcursive movements (especially duringparafunction). The benefits to themasticatory organ include decreasedmasticatory muscle activity,3–6 minimizedlateral forces, and subsequent decreasedincidence of dental disease on posteriorteeth,7 and a mechanical advantage to thesystem by lowering the forces on the anteriorteeth through the physics of a class 3 leversystem.8,9

It has been clearly stated in the literature thatmasticatory muscle activity increases as thenumber of guidance surfaces increases fromanterior to posterior.3–6 Most recently, Tamakishowed the effect of changing the guidancesystem from canine guidance to variablegroup function of 2–5 contacts onmasticatory muscle activity as illustrated inFigure 4.10

Several authors have shown significant effectsof occlusal discrepancy on periodontaldisease.7 Goldstein showed significantreduction in mean periodontal scores withcanine protected occlusions.7 Greenconducted an extensive literature review andfound significant reduction in periodontaldisease with occlusal therapy (specificallyequilibration). Burgett found a significantincrease in attachment width after two yearswith equilibration before surgery comparedto no equilibration. Bernhardt cross sectionalstudy of 4,310 patients demonstrated astatistically significant relationship betweennon-working contacts, attachment loss, andincreased probing depths. Svanberg showedthat occlusal trauma accelerates attachmentloss in periodontitis. Moozeh found thatreduction in mobility was significantlygreatest in the group that had non-workinginterferences completely removed comparedto the group that had them left in “harmony.”Harrel and Nunn in a comprehensive studycompared treated and untreated patients forocclusal discrepancies. Their study showsstrong evidence of an association betweenuntreated occlusal discrepancies and theprogression of periodontal disease! Severalstudies by Japanese authors includingOhmori and Tamaki have shown evidence ofincreased severity of periodontal disease withgroup function occlusions and bilateralbalance occlusions compared to canine

Figure 2. Canine dominant occlusion does not equalcanine protected occlusion. With posturaluprighting, brain lateralization and speechdevelopment, the canine has regressed into thedental arches.

Figure 3. The ultimate goal of any anteriorguidance concept should be, to disoccludeposterior teeth during lateral or protrusivemovements. Canine guidance (CG) describescomplete bilateral posterior disocclusion withlateral guidance the sole responsibility of thecuspid. Group function (GF) describes balancingside disocclusion with multiple guidance surfaceson the working side. Balanced occlusion (BO)describes bilateral occlusal contacts during lateralexcursions.

Figure 4. EMG data from study shows lowest levels of muscle activity with canine guidance with similarresults for sequential contacts including first and second bicuspids. There is a significant (2×) increasein the EMG activity when the group function includes the 6s and 7s. Adapted from Tamaki et al.10

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guided occlusion (Figure 5).

The third and least discussed advantage ofanterior guidance is the mechanicaladvantage imparted to the stomatognathicsystem by a class 3 lever.

The further the guidance system is from thetemporomandibular joint (TMJ) the lowerthe level of work/force exerted for a givenpower/load. This concept is importantbecause it acknowledges that despite the factthat no occlusal system can be without lateralforces, they can be reduced as we move awayfrom the joint.18 In clinical practice thisphenomena is frequently seen as, the anteriorteeth with their small conical roots and lackof periodontal support are often the last teethin the mouth to be lost. The canine is ideallysuited for this dominant role in lateralguidance because of its position in the dentalarch relative to its distance from the TMJ, itsanatomy and its proprioceptive capacityrelative to other dental structures (Figure 7).19

The term, anterior guidance is misleadingbecause it suggests that all the anterior teethhave a disclusive function. The anterior teethare considered a functional unit, however, thecentral incisors are not part of anylaterotrusive control. They are actuallyavoided during mastication. They do,however, play a dominant role inproprioceptive signalling and are adeterminant in the frontal area end point ofthe masticatory cycle and speech.20,21

The lateral incisor has a highly variableposition in the dental arches relative to itsverticality and rotation. It has somelaterotrusive control function primarily


Figure 5. B-1 canine guided, B-2 group Function, B-3 bilateral balance. In the population studiedOhmori classified the study group with slight,moderate, and severe inflammation according toLindhe and found there was an even distributionof occlusal patterns in the mild inflammationgroup. There was no significant differencebetween cuspid guidance and the group functionguidance in the moderate inflammation groupbut a significant increase in periodontal diseasewith bilateral contact occlusion. With the severeinflammation group there was a significantincrease in periodontal disease with occlusalschemes that have multiple lateral contacts.Adapted from Ohmori et al.17

Figure 6. A class 1 lever is the most efficient and does the most work with the least applied force. Ideallythe jaw lever functions as a class 3 lever. The temporomandibular joint is the fulcrum (F), the massetermuscle, temporalis muscle, and medial pterygoid muscle provide most of the force (P) near the fulcrum,and the work (W) is done by the teeth along the dental arches.

Figure.7 Patient showing severe anterior wear.Anterior guidance that is not in harmony withposterior occlusion, occlusal plane, condylarpathways, creating a class 1 lever. If during aprotrusive movement there is a heavy contact ofposterior teeth, the molars overpower the TMJ asthe fulcrum (F), the power is supplied by themuscles behind theses teeth (P) and a muchgreater work/load is transmitted to the anteriorteeth as a class 1 lever system.

Figure 8. Sequential class 1 wax-up showing protrusive guidance inclines of lower first bicuspid and thedistal marginal ridge incline of the upper cuspid (blue wax incline on cuspid).



during maturation of the developingdentition. It then becomes part of theanterior functional unit along with the canineafter maturation. In a class1 dental situationimmediate disocclusion of posterior teethcomes from contact of the lower firstbicuspid with the distal marginal ridge of theupper cuspid during protrusive movements(Figure 8).

Posterior disocclusion resulting fromcondylar movement is the other dominantcomponent. The interrelationship betweenanterior guidance and posterior guidance willbe discussed later in the article. Furtherdisocclusion comes from the contact of thelower incisors with the lingual contact of theupper incisors. This typically is not thedeepest concavity of these teeth but theprominent marginal ridges (Figure 9).

The functional unit illustrated in green inFigure 10 is not the primary disocclusive unitin protrusion. This unit normally functionsas a proprioceptive control for mandibularmovement and speech when the posteriorocclusion and joint dynamics are in harmony.

Now that we have discussed what anteriorguidance is, our next topic is to develop atherapeutic rationale for how much of it weneed? Is there a normal value that we can usefor our therapies or is it highly variable? Whatif we have too steep a guidance system? Whatif it is too shallow? Slacicek, Sato, andMcHorris, measured the lingual concavityangle of orthodontic normals, relative to theaxis orbital plane.8,9,20 Research by Slavicek,Sato, and McHorris, of non orthodonticnormals showed a consistent disocclusionangle for the lingual concavity of each tooth,even among different populations.

Why can’t we use these norms to apply to ourtherapy? Like most of the research that hasbeen done on occlusion and its associationwith TMD, the answer is complicated!

This research further looked at condylarfunctional movement tracings and showed ahigh correlation between the disocclusionangle and condylar guidance angle for thecanine (Figure 13).20,8 However, when we tryto apply this data into the general dentalpopulation, the individual variability makesit impossible to establish clinically usefulnorms that yield consistent results. Therefore“clinical application must be assessed on anindividual basis.”22

Remember, the ultimate goal is disocclusionof posterior teeth. Anterior control is onlyone of the variables. As therapists we need tounderstand the role of each variable in orderto provide optimal treatment for ourpatients. It is beyond the scope of this articleto address all of these parameters; however,we must consider the effect of (1) anteriordisclusive angle (CI); (2) posterior condylarguidance angle (HCI); (3) cusped teethversus flatter teeth; and (4) occlusal planeinclination (OPI).

These four variables will determine theamount of disocclusion for every patient. As

Figure 9. McHorris, noted that disclusive lingualsurface angle is most often the mesial and distalmarginal ridges. There can be as much as a 35�differential between the concavity and themarginal ridge.

Figure 10. The functional unit illustrated in green.

Figure 11 and 12. Slavicek, Sato and McHorris measured the lingual concavity angle relative to the axisorbital plane on three different populations and found similar trends in steepness of angle, sequentialdecrease in angle from anterior to posterior and length of guidance contact surface. (Adapted fromSlavicek R. Okklusionkonzepte, IOK 3-4/1982; Slavicek R. Die Functionellen Determinanten desKauorganes, 1984)

Figure13. Relationship of anterior disocclusionangle and functional condylar guidance ledresearchers to assert that the anterior guidanceangle should be within a range of 0 to 10 degreesof the condylar guidance angle. (Adapted fromSlavicek R. Okklusionkonzepte, IOK 3-4/1982;Slavicek R. Die Functionellen Determinanten desKauorganes, 1984)

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therapists we are able to change or modify thedental structures to accommodate thefunctional condylar anatomy to disoccludeposterior teeth for optimal efficiency. Toolittle disocclusion during functionalmovements may cause interferences duringparafunctional loading. Too muchdisocclusion creates excess separation of

posterior teeth during functional movementsand will be inefficient for chewing. Slavicekfelt that considering parafunctional loadingand mandibular deformation the idealamount of disocclusion for maximumefficiency would be in the range of 6–8degrees.20

Dr. Martin Mai, (Vienna Austria personalcommunication) developed this conceptfurther and coined the phrase “FunctionalGeometry” where he illustrated the impactthat changing these variables will have on theamount of disocclusion or interferencecreated by our therapeutic design concept(Figures 14 and 15).

The last question is “What if anteriorguidance is too steep?” Anyone who has everplaced anterior crowns recognizes the clinicalsignificance of interfering with this delicatebalance of adaption and harmonization. Thisis not a case of “if a little anterior guidance isgood, more will be better!” Severalresearchers have shown that for harmony,Anterior guidance should be equal to orgreater than posterior condylar guidance.23

The literature reports a range of 0–10degrees.

What if we err on the side of ”moredisocclusion is better?” What if we increaseor steepen our therapeutic anterior guidancebeyond 10 degrees? Several researchers haveshown that artificially steepening canineguidance will alter muscle activity. One of themost novel research protocols on this topic isan experimental design by Tamaki where he


Figure 14. Axis orbital plane (AOP) is used as the reference plane as it corresponds to most commonlyused articulator systems. Horizontal condylar inclination (SCI) is patient specific and derived fromcondylar tracking device. Anterior guidance angle (IGI) is variable component and can be used/changedby therapy. Occlusal plane inclination (OPI) is defined as a plane from tip of lower central incisor to tipof distobuccal cusp of lower six year molar. The intersection of the IGI and SCI with the occlusal planecreate relative incisal guidance angle (RIGI) and relative condylar inclinations (RCI), respectively.

Figure 15. This figure illustrates how functional geometry concepts can be used to predict and designtherapies that will provide the appropriate amount of posterior disocclusion. Assuming a 33° cuspinclination (CI) and a known horizontal condylar inclination (HCI) of 45° it is clear how altering onlyone parameter can have a significant impact on the amount of posterior disocclusion! For example:HCI-OPI=RCI, RCI-CI= amount of disocclusion. 45°�12°=33°, RCI-CI=0 no disocclusion available(contactsinevitable)! 45°�2°=43°, RCI-CI=10° adequate disocclusion available (good function). 45°�(�6)°=51°, RCI-CI=18° too much disocclusion! (inefficient chewing).

Figure 16. The anterior teeth could be consideredthe guardians of the posterior teeth during anyeccentric bruxing attempts. If they are properlycoupled all bruxing forces become theresponsibility of the anterior teeth, and all frictionto include possible wear, becomes their burden.This amount of friction can be controlled howeverto insure their integrity by providing a disclusiveangle that is identical to the condylar disclusiveangle (1:1 ratio). Anterior disclusion significantlyreduces the electrical activity of the powerfulmasseter and pterygoid musculature. Anteriorteeth disclusion allows the mandible to workwithin a class 3 lever principle (Adapted fromMcHorris23).



artificially induced increasing canineguidance through cast gold lingual onlaysprovisionally cemented on dental students.He altered their guidance system, startingwith a canine guidance that was equal tocondylar guidance and then steepening theguidance in 5-degree increments. He thenlooked at the effect this had on condylarmovement pathways and on muscleactivity.10

At 10 degrees and greater the condylarmovement pathway showed a definiteretrusive, surtrusive movement on theworking condyle. Clinically this would not beapparent but one can hypothesize that thistype of movement has the potential to be verydestructive to the retrodiscal component ofthe disc-condyle assembly. This phenomenawas also mentioned by Coffee, Mahan andGibbs in 1989.24

They felt that this effect of tooth guidance oncondylar movement was an unexpectedfinding and warranted further research to seeif there was a correlation with TMD! Parlettfound a high correlation between theseretrusive and surtrusive condylar movementson the working side condyle and theincidence of internal dearangement.25

In 1981, Kirveskari wrote, “that negligiblefunctional tooth wear has brought aboutchanges to the form-function harmony of thestomatognathic system exemplified by thepersistence of cusps and vertical overbite ofanterior teeth. It appears that the presence ofcusps can be easily tolerated provided thattheir form is accommodated to the jointfunction. However, anterior guidance isusually necessary for this requirement to bemet.”26

Treatment strategies should be based not onthe original heavy masticatory function buton the present day condition whereparafunction is the new enemy of our dentalrestorations. Anterior guidance in harmonywith the cusps of teeth and the TMJ will helpto decrease masticatory muscle activity,minimize lateral forces on posterior teeth,and create a mechanical advantage to thesystem of the lowering of forces on theanterior teeth by insuring a class 3 leversystem. Harmonizing all of these components

will allow you to create a therapeutic conceptindividualized for each patient that optimizesfunction, muscle efficiency and maximumprotection from the pathologic levels of forceconsistent with parafunction.


References1. D’Amico A. J Prosthet Dent 1961;(2):5. 2. Beyron H. Occlusal relations and

mastication in Australian Aborigines. Acta Odontol Scand 1964;22:597–678.

3. Manns A, Chan C, Miralles R. Influenceof group function and canine guidance on electromyographic activity of elevatormuscles J Prosthet Dent 1987;57:494–501.

4. Moller E. Action of the muscles of mastication. Frontiers of Oral PhysiologyVol. 1. Farmington, CT: S. Karger; 1974,121–58.

5. Shupe RJ, Mohamed SE, Christensen LV,Finger IM, Wienberg R. Effects of occlusal guidance on jaw muscle activity.J Prosthet Dent 1984;51:811–18.

6. Williamson EH, Lundquist DO. Anteriorguidance; its effect on electromyographicactivity of temporal and masseter muscles. J Prosthet Dents 1983;49:816–23.

7. Huffman RW, Regenos JW, and Taylor RR. Principles of occlusion, laboratory and clinical teaching manual (2nd ed). Columbus, OH: H&R Press; 1969.

8. McHorris WH. Occlusion with particular emphasis on the functional and parafunctional role of anterior teeth:Part 1. J Clin Orthod 1979;13(9):606–20.

9. McHorris WH, Occlusion with particular emphasis on the functional and parafunctional role of anterior teeth:Part 2. J Clin Orthod 1979;13(10)684–701.

10. Tamaki K. A thesis submitted in partial fulfillment of the requirements for the degree of Masters of Science in Dental Sciences. Donau University, Krems, Austria: August 5, 2004.

11. Green MS and Levine DF. Occlusion andthe periodontium: a review and rationalefor treatment. J Calif Dent Assoc 1996;24(10):19–27.

12. Burgett FG, Ramford ST, Nissle RR, et al.A randomised trial of occlusal

adjustment in the treatment of periodontitis patients. J Clin Periodontol1992;19:381–88.

14. Goldstein. JPD. 1979.13. Bernhardt O, Gesch D, Look JO, et al.

The influence of dynamic occlusal interferences on probing depth and attachment level: results of the study of health in Pomerania (SHIP). J Periodontol. 2006;77(3):506–16.

15. Svanberg G, et al. Occlusal considerations in periodontology. Perio2000 1995;9 106–17.

16 Moozeh MB, Suit SR, Bissada NF. Toothmobility measurements following two methods of eliminating nonworking sideocclusal interferences. J Clin Periodontol1981;8(5):424–30.

17 Harrell SK and Nunn ME. The effect of occlusal discrepancies on periodontitis I.Relationship of initial occlusal discrepancies to initial clinical parameters. J Periodontol 2001;72(4):485–94.

18 Ohmori et al Japan J Periodont 1995.19. Levy JH. Ultrastructural deformations

and proprioceptive function in human teeth. Thesis. New York University College of Dentistry: New York; 1995.

20 Slavicek.R.,Die functionellen Determinanten des Kauorgans, Habiltationsschrift, Wien 1982.

21. Gibbs et.al. A Comparative study in complete denture wearers and natural dentition subjects. JPD 1985.

22. Pelletier LB and Campbell SD. Evaluation of the relationship between anterior and posterior functionally disclusive angles. Part II: Study of a population J Prosthet Dent 1990;63(5):536–40.

23. McHorris WH. Focus on anterior guidance. J Gnathology 1989;8:3–13.

24 Coffey JP, Mahan PE, Gibbs CH, WelschBB. A Preliminary study of the effects oftooth guidance on working side condylarmovement. J Prosthet Dent 1989;62(2):157–62.

25. Parlett KG. A thesis submitted in partialfulfillment of the requirements for the degree of masters of science in dental sciences. Donau University, Krems, Austria; August 5, 2004.

26. Kirveskari P. Anterior guidance in stomatognathic function. Proc Finn Dent Soc 1981;77:73–78.

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OCCLUSION

Brief History of Occlusion in the 19th and 20th CenturiesUne brève histoire de l’occlusion aux 19e et 20e siècles

By Dr. Ian W. Tester DDS, MSc

About the Author

Dr. Ian Tester graduated from the University of Toronto with a DDS degree in 1982 and a master’s of sciencein dental sciences degree from Donau University in Krem’s Austria in 2004 with the major emphasis on thetreatment of the complicated patient utilizing orthodontics, prosthetic dentistry, physical therapy and med-ical intervention. Dr. Tester practices general dentistry in St. Catharines, Ontario with a focus on multidisci-plinary treatment of the complex dental patient. Dr. Tester lectures in the US. and Canada on the topics ofTMD, function and dysfunction, esthetic and restorative dentistry, occlusion, and prosthetics.

ABSTRACTThe preponderance of literature reviews and lack of new basic research in North America emphasizes the need to reflect on the his-tory of the science of occlusion so that we can design appropriate evidence-based studies. The ultimate goal must be a consensusthat is backed by sound scientific research. A review of the evolution of the term occlusion throughout the late 19th and 20th centuryreveals a history marked by much dogma and controversy. Careful study also reveals some excellent research that should provide aframework for future studies as well as a good deal of useful information that can be applied in our therapies today. This paper offersa brief overview of the history of occlusion and temporomandibular dysfunction research.

RÉSUMÉLa prépondérance des analyses documentaires et l’absence de nouvelle recherche fondamentale en Amérique du Nord font ressortir lebesoin de tenir compte de l’historique de la science de l’occlusion afin de pouvoir concevoir des études factuelles adéquates. Le butultime est d’obtenir un consensus qui est appuyé par une recherche scientifique solide. Un examen de l’évolution du terme occlusionvers la fin du 19e siècle et au 20e siècle révèle une histoire marquée de dogmatisme et de controverse. Un examen minutieux révèleégalement une recherche excellente qui devrait fournir la structure pour les prochaines études ainsi que beaucoup d’informations utilesqui peuvent être appliquées aux traitements actuels. Cet article donne une brève vue d’ensemble de l’historique de l’occlusion et de larecherche sur la dysfonction de l’articulation temporomandibulaire.

Albert Einstein (1879–1955) wrote that“truth is what stands the test of

experience.” The study of occlusion and itsimportance to health and restorative successcannot be overemphasized. The polarization ofclinicians into the broad categories of“occlusionists” and “non-occlusionists” hasdone little to foster current research intodiagnostic and therapeutic modalities relatedto occlusion. The preponderance of literaturereviews and lack of new basic research in NorthAmerica emphasizes the need to reflect on thehistory of the science of occlusion so that wecan design appropriate evidence-based studies.The ultimate goal must be a consensus that isbacked by sound scientific research. A reviewof the evolution of the term occlusionthroughout the late 19th and 20th centuryreveals a history marked by much dogma and

controversy. Careful study also reveals someexcellent research that should provide aframework for future studies and a good dealof useful information that can be applied inour therapies today. The years 1870 to 1970 sawmuch of the groundwork laid for our currentunderstanding of occlusion. In addition, muchof the perceived controversy revolving aroundthe science of occlusion dates back to mythsperpetuated from this period.

The complexity of the stomatognathic systemand challenges faced in studying such anintricate structure are made even more difficultby the terminology that is used. The currentunderstanding of the word “occlusion” ishistorically inaccurate and the term is moreappropriately defined as “articulation of theteeth and temporomandibular joints.” A study

of the history of occlusion requires abroadening of the scope to include a review ofthe history of gnathology. Gnathology asdefined in The Journal of Prosthetic DentistryGlossary of Prosthodontic Terms is “thescience that treats the biology of themasticatory mechanism as a whole: that is, themorphology, anatomy, histology, physiology,pathology, and the therapeutics of the jaws ormasticatory system and the teeth as they relateto the health of the whole body, includingapplicable diagnostic, therapeutic, andrehabilitation procedures.”1 The termgnathology was originally suggested by HarveyStallard in 1924 and is a combination of theGreek terms “gnathos” meaning jaw and“ology” meaning the study of early history.2

Early understanding of the function of the

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temporomandibular joint dates back to thefirst edition of Gray’s Anatomy which waswritten and published by Henry Gray inEngland in 1858. Gray recognized that thetemporomandibular joint was capable ofboth hinge as well as sliding action. Hetermed this a “ginglymo-arthrodial joint.”Earlier, Balkwell (1824) of England noted thesliding action of the joint; however, thisresearch was largely ignored in NorthAmerica until the time of Bonwill (1858)who believed the transverse movements werein a straight line forward. He was a proponentof balanced occlusion and believed that a fourinch distance existed between the condylesand the distance from each condyle to thelower incisor was also four inches. Thistriangular theory led to the development ofthe Bonwill articulator. Other notable 19thcentury contributions were made by Snow(development of the facebow for transfer ofthe hinge axis), Sigmund (1870) andFerdinand Graf von Spee of Kiel, Germanywho described the correlation between thecurved arrangement of the occlusal planes ofteeth and the curves of condylar paths(1890).2–18 Finally, W.E. Walker (1897)modified Bonwill’s earlier articulator toreflect the fact that the condylar path was notparallel to the occlusal plane. The Walker-Bonwill articulator which later evolved intothe Walker physiological articulator was usedin combination with anatomical teeth thatWalker based on his evaluation of the naturaldentition. This created a more accuratetransference from articulator to the mouthwith respect to function. In addition, Walkerdeveloped the facial clinometer whichallowed measurement of the direction of thecondylar paths and occlusal plane relative tothe facial plane. It is clear that the principlesof jaw movement were well defined by theend of 19th century.2–7

1900–1950Alfred Gysi of Zurich, Switzerland (1865–1957) was responsible for many importantdevelopments including recordings of thehinge axis and the development ofanatomical teeth that were based on a 33degree condylar inclination (Trubyte teeth).Gysi also discussed grinding these teeth tocreate a mortar and pestle effect (laterdescribed as lingualized occlusion throughthe work of Brenner and Payne – 1940). Gysi

graduated from the University of Geneva in1886 and opened his own practice in 1891 inZurich. In addition to significantcontributions to the fields of photography,botany, and histology he conductedimportant research in the fields ofProsthodontics and occlusion after the turnof the century.4

Norman Bennett originally described theBennett Movement (side shift of the rotatingcondyle) in 1908 using instrumentationcalled a gnathograph. Monson developed thespherical theory of occlusion which wasbased on a combination of Bonwill’s fourinch triangle; Von Spee’s compensating curveand Balkwell/Christensen’s condylarmovements in three dimensions. Hanau(1923) disagreed with Monson anddeveloped the Hanau articulator to producebilateral balanced occlusion with articulatormovements designed to reflect mandibularmovements. Meyer (1933) proposed using afunctionally generated path to produce afunctional occlusion.3,8

Pankey and Mann (Pankey-Mann system)combined the Monson four inch sphere andMeyer’s functionally generated path toproduce bilateral balanced occlusion. Later,Schuyler’s influence allowed the developmentof the Pankey, Mann, Schuyler system (PMS)which was a combination of incisal guidance,long centric and posterior separation of teethin excursions.2

B.B. McCollum formed the GnathologicalSociety in 1926 and proceeded to guide thisorganization in refining research intomandibular movement. Initially he modifieda Snow facebow which he rigidly attached tothe mandibular teeth with compound. Using

small pencils he demonstrated the presenceof a distinct rotational hinge axis. Afterconfirming the existence of the hinge axisMcCollum lead the Gnathological Society ofCalifornia to investigate the work begun byBalkwell, Walker, Gysi, and others usinginstrumentation similar to Gysi’s andWalker’s that was rigidly fixed to themandible and more precise. In addition theydeveloped a functional clutch that could befixed to the mandible without interferencewith intercuspation during the studies. Dr.McCollum was a proponent of balancedocclusion which had been popularizedthrough previous complete denture studies.His laboratory technician, Everitt Paynedeveloped the incremental wax builduptechniques used today to create the balancedocclusion. Dr. Charles Stuart, anothermember of the gnathological society teamedup with Dr. McCollum to produce the firstsemi-adjustable articulator deemed theMcCollum Gnathoscope in 1930 and theMcCollum gnathograph in 1934. Thisinstrument recorded mandibular movementon extra oral plates.5

Harvey Stallard is credited with defining andpostulating the “structural and functionalunit” which was the term used to define theanterior teeth working to produce a mutuallyprotected occlusion (disocclusion of theposterior teeth). As a member of theGnathologic Society this created two distinctbelief systems within the group. Stallard andStuart were proponents of anterior guidance(Mutually protected occlusion or cuspidprotection) while McCollum and Payne werein favour of balanced occlusion.

The years prior to 1950 were ultimately aperiod that could be termed “The Dawn of


Figure 1. Alfred Gysi. Figure 2. McCollum gnathoscope.


A BRIEF HISTORY OF OCCLUSION IN THE 19TH AND 20TH CENTURIES

Gnathology.” Many concepts wereintroduced that emphasized excellence andprecision with respect to reconstruction. It isimportant to note that much of the literaturefocused on an “inside-out” movement of themandible. A paradigm shift occurred in the1950s when research began to look at“outside-in” mandibular movement that wasmore representative of function. Theconcentration on the posterior determinantsof occlusion (temporomandibular jointcondylar inclination and Bennett movement)was also lessened with anterior guidancetaking a prominent place in the literature.

1950–TodayIn the second half of the 20th century, Gerberand the Swiss school popularized lingualocclusion. This was one of four dogmaticocclusal theories being promoted. Groupfunction (Byron and later Pankey, Mann),cuspid guidance (Stuart and Stallard) andbalanced occlusion (McCollum, Payne) wereall purported to be the best occlusal scheme.

The 1950s and 1960s provided a wealth ofinformation about mandibular movementand stomatognathic function. Posselt (1952)in his classic gnatho-thesiometer studies wasable to identify the habitual and extremepositions of mandibular movement.10–12

Posselt’s research recognized the envelope offunction which Ahlgren (1966) verified.Moller19 (1966) used electromyography tostudy the actions of the muscles inmastication further adding to the literaturebase that emphasized function.

McCollum and Stuart published their classic“Research Report” in 1955 whichsummarized the philosophy of capturingmandibular movements, accurate transfer ofcasts and the use of an Arcon typearticulator.2,6 Stuart fabricated the Stuartarticulator with gnathological settings thatallowed use of accurate transfer of modelsand articular movements. Subsequently,Guichet designed the Denar pantograph fordetermining condylographic movements andarticulator settings and many practitionersadopted the Denar articulator system forroutine prosthetic dentistry.3,20

Woefel (1957) provided electromyographicevidence supporting the mandibular hinge

axis theory. Using needle electromyographyhe identified a lack of external ptyregoidactivity during initial hinge opening followedby contraction during protrusive movements.13

Brotman further developed hinge axistheory.14 The stage was set for the 1960s asresearch attempted to expand on the theoriesdeveloped to date. Centric relation and itsdefinition dominated much of the research.

Granger21 (1960) reiterated the necessity ofproper hinge axis location and transferencewhile Cohen22 (1960) noted that centricrelation occurred at the only point inmandibular position where the mandibleunderwent pure rotation. Cohen alsodescribed three different slopes of the glenoidfossa. He felt that the shallowest fossa was themost tolerant to aberrant closure patternswhich caused the condyle to seat improperly.The steeper eminence led to the most lateralstrain on the teeth and pathology in the joint.Hinge axis location was deemed necessary todetermine if centric occlusion was inharmony with centric relation. In addition,vertical dimension changes on the articulatordid not affect the centric relation position ifthe hinge axis was correctly recorded. Theaxis of rotation of the ginglymoid part of thejoint was described as being 5 mm below thecenter of each condyle by Naylor23 (1962).Boucher24 (1962) discussed growth anddevelopment of the articular eminence. Thefossa is shallow at birth and graduallydeepens thereafter. The eminence starts toform at age 7 to 9 years. This developmentaccelerates during the 10th and 11th years. Bythe 13th year the articular eminence hasusually attained adult proportions. Slightflattening occurs after the age of 40.

D’Amico25 (1961) reviewed the function ofnatural teeth reporting to the Academy ofRestorative Dentistry in Chicago. Heconcluded that the study of the evolution ofnatural teeth of the primate family did notsupport von Spee’s observations or thetheory of balanced occlusion. His attritionstudies on pre-white California Indians notedthat the heavy attrition recorded was dietrelated and not an evolutionary response. Hefurther illustrated the role that the cuspidsplayed in avoidance of deleterious lateralforces. Periodontal failure due to occlusalforces was reduced by the elimination of

traumatic antagonist tooth forces.

Schuyler26 (1963) in a classic article onanterior guidance noted its importance asequalling or surpassing the temporo-mandibular joints (TMJs) in influence on thefunctional occlusion of the dentition. Theincisal guidance does not have the flexibilityof the TMJs for adaptation. Schuyler notedthat the condylar pathways had littleinfluence on the incisal guidance; conversely,the incisal guidance did have an influence onthe development of the glenoid fossa. Hestressed that an improper anterior guidancecould produce an abnormal movementpattern of the condyles. Mounted diagnosticcasts were used to establish the pre-existingincisal guidance. In combination with thefunctionally generated path technique andproper anterior guidance a “freedom incentric” ensured a non-locked posteriorocclusion.

Lucia27 (1964) defined centric relation as theintersection of the centers of vertical arcingand lateral motion in each condyle when theyare in the most posterior terminal position inrelation to the maxilla. The need to removethe proprioceptive influence of the teeth thatleads to muscle programming was describedby Guichet.20 Okeson termed thisprogramming “muscle engrams.” Lucia feltthat removal of muscle engrams dictated bytooth contact would allow a perfect hinge axisclosure in centric relation. Glickman (1966)defined CR as the most retruded position ofthe mandible to which the mandible could becarried by the patient’s own musculature.Graber (1966) defined it as an unstrainedneutral position of the mandible neitherdeviating to the left or right nor protruded orretruded. Goldman, Cohen (1968) believedcentric relation to be the most posteriorrelationship of the mandible to the maxillafrom which lateral excursions could bemade.21 In 1969 Jankelson reported on thestimulation by Myomonitor of cranial nervesV and VII as a method of producing a“physiologic rest” position of the muscleswhich became the basis of neuromuscularocclusion.15 Subsequent research by Remeinand Ash refuted this position as it was non-reproducible and created an anterior-inferiorcondylar position from CR.16

TESTER

Long28 (1973) described the use of a leafgauge to seat the condyles through the use ofthe elevator muscles. This gauge consisted ofmultiple leaves 0.5 inches wide and 0.01inches thick. The effect of anteriordeprogramming and the production of aclass three lever braces the condyle against thearticular disk on the posterior slope of theeminence. Williamson’s29 technique beganwith 10 leaves being placed between theupper and lower incisors. Leaves wereremoved until the teeth initially contacted.One leaf was added sequentially until thepatient felt no posterior contact when bitingfor 5 minutes. This time period was based onJarabak’s work that aberrant neuromuscularelectromyography recordings returned 5minutes after splint removal.30 The last leafwas removed and the bite registration wastaken ostensibly in a centric relation position.

Celenza8 (1973) described centric relation asthe most important spatial relationship of themandible to the maxilla. He defined thisposition as the most retruded position of themandible and stated that it must berepeatable and consistent. Guided andunguided gothic arch techniques and guidedbiting point methods were used. No statisticaldifferences were noted between all threetechniques. Lundeen31–34 described centricrelation as the most superior posteriorposition of the condyles.

Weinberg (1975) used transcranialradiography to study condylar position withrespect to TMD. He recognized the multi-causality of the condition and believed thatlateral transcranials radiographs that wereanatomically aligned would identify condylarmisalignment created by deflective occlusalcontacts. Concentric 2-dimensional positionwas the goal.2,35 Williamson35 (1978) notedthat tomographs provided superiordiagnostic information to transcranialswhich he used to substantiate Dawson’s37

hypothesis that centric relation was asuperior position of the condyles bracedagainst the posterior slope of the articulareminence. In a paper published in 1983Gilboe38 described the posterior limitation ofcondylar movement as dictated by the intra-articular tissue and the eminence, not by theconcept of condyle-fossa spatial relationship.He defined centric relation as “the most

superior position of the mandibular condyleswith the central bearing area of the disk incontact with the articular surface of thecondyle and the articular eminence.” Gilboedescribed the bimanual manipulationtechnique of Dawson as creating a posteriordirected force on the mandible with asimultaneous superoanterior force created bythe elevator muscles positioning the condyleagainst the eminence and disk. He felt thatanterior deprogrammers created a similarforce vector however Guichet’s chin pointguidance technique pushed the condyles tooposterior away from the eminence. Thecapsular ligament was noted to be responsiblefor maintaining the central bearing area ofthe disk against the condyle. Thetemporomandibular ligament limitsposterior movement of the condyle pivotingit against the eminence when maximallystretched.

Lundeen, Shyrock and Gibbs39 (1979) studiedmandibular border movements using plasticblocks engraved by air-turbine drills. Theyconcluded that patients with excessiveBennett movement (3.5mm +) and little orno anterior guidance were the mostchallenging to restore as the elimination ofeccentric cusp interference was extremelydifficult. A fully adjustable articulator wasrecommended with condylar recordingsincluding Bennett movement. Patients withminimal Bennett movement (.75 mm or less)had molar cusp heights that were steeper andreflected the anterior guidance and non-working condylar pathway (posteriordeterminant). These patients could berestored adequately on a semi-adjustablearticulator. The study of 163 subjects notethat 80% had a Bennett movement of 1.5 mmor less with the average being .75 mm.

Williamson and Lundquist17 (1979)concluded that if posterior teeth wereseparated by a leaf gauge the temporalmuscles remained active while the massettermuscles showed minimal electromyographicactivity. In excursive movements when theposterior teeth were kept from touching (i.e.,anterior guidance) a marked reduction ofmassetter and anterior temporalis on themediotrusive side and reduction of massetteractivity on the laterotrusive side was noted. Ifthe anterior guidance was eliminated muscle

activity in excursions was not reduced. It wasalso stated that the absence of lateral forceson the posterior teeth was desirable whichagain supported anterior guidance.

McHorris40,41 discussed occlusal schemes andthe functional role of teeth emphasizinganterior determinants that are coordinatedwith appropriate occlusal plane angles as wellas posterior determinants. He described cuspfossa and cusp embrasure occlusions andnoted that steep eminences allow steeperanterior teeth slideways while shalloweminences require shallow front toothslideways.

Mahan and Gibbs (1984) identified theactions of the external ptyregoid superior andinferior heads during opening and closingmovements. The superior head was found tocontract on closure stabilizing the articulardisc while the inferior head was active duringtranslation laterally and protrusively.2,42

Woods43 (1988) further described centricrelation as a border position that may berelated to the horizontal hinge axis. Thisposition was described as a repeatable,anatomical and physiologically stablerelationship of the condyle maximally bracedagainst the thinnest part of the disk againstthe eminence. The centric relation positionwas commonly not coincident with theintercuspal position of the teeth. Woodsemphasized that centric relation is a referenceposition used by the dentist to accuratelytransfer pantographic tracings and thepatient’s models to an articulator. Roth44,45

combined deprogramming with a bimanualmanipulation technique using Delar wax(Delar Corp.). By chilling three thicknesses ofwax placed on the anterior teeth after centricregistration the patient was instructed to bitehard into soft wax placed on the posteriorteeth. In this way the elevator musclesprovided a superior anterior force whichproved to be an accurate and repeatablemethod of taking a centric relation record ina normal patient group. Carr46 failed to findany physiologic basis for the use of a leafgauge to deprogram muscles usingelectromyography after 15 minutes of leafgauging.

Jensen26 (1990) described the effect of jaw size




on occlusion terming it the “5th factor.” Withclass II and class III malocclusions theanterior determinants of occlusion werereduced or eliminated from the guidancescheme. Using a hypothetical mandibularmodel he illustrated the various strains thatcould occur in tooth to tooth contact as thearches widened and narrowed. In addition,the increasing importance of posteriordeterminants in the absence of anteriorguidance as well as the need to create a propergroup function guidance mechanism usingthe bicuspids and first molar were discussed.The increasing potential for production of aclass III lever system was reported.

Kinderknecht et al.47 (1992) used an Axiotronto study terminal hinge axis location anddeprogramming. Their conclusion was thatin healthy subjects the amount of positionalchange in the TTHA after 12 hours ofdeprogramming with a custom anteriordeprogrammer made out of stent materialand orthodontic resin was not statisticallysignificant. In addition, they concluded thatthe Axiotron was a valid tool for in vivo studyof the terminal transverse hinge axis.Numerous other authors have reported onthe validity of using electroniccondylography to describe condylarposition.11,23,48–51 In a normal healthyindividual the repeatability of the maximumintercuspation position can be verified.

Dawson52 (1995) recognized that somestructurally deformed TMJs functionadequately and are comfortable in cranialloading despite the fact that they could notmeet the requirements of a true centricrelation position. He termed their position asadapted centric posture (ACP). Slavicek53 hasused the terms reference position (RP) andderanged reference position (DRP) in placeof CR and ACP. RP is defined as the retralborder position of the mandible with thejoint structures unstressed. DRP is thereference position of a joint that has aderanged disc.

Wiskott and Belser54 (1995) reviewed thehistory of various occlusal schemes andproposed a simplified scheme for occlusaldesign in restorative dentistry. Observationsof natural dentitions revealed (1) occlusalcontacts (OC) were fewer and less ideally

placed relative to ideal schemes; (2)functional and parafunctional forces werenot directed along the long axes of teeth only;(3) the terminal hinge axis is neitherabsolutely stable nor absolutely reproducible;(4) unstrained lateral movements have asmaller envelope of motion than strainedmovements; and (5) position of teethdepends on forces of low intensity and longduration and tooth stability is mostlyindependent of occlusal relationships. Asimplified pattern of OC should follow theseguidelines and allow adequate function,esthetic demands and be applicable to smalland large restorations ensuring stability. Theprimary characteristics outlined by theauthors were (1) anterior guidance; (2) atleast one buccal cusp of a mandibular toothoccludes with the central fossa of a maxillary tooth neutralizing eruptive force; (3) proximal contacts are necessary tostabilize the teeth mesiodistally; (4) OC mustbe designed to allow room for variability inTMJ movement; and (5) cusp to fossa contactshould be a definite bearing surface asopposed to a point to reduce the force persurface area and reduce wear. They furtherconcluded that immediate side shift (ISS)would create concave internal slopes of cuspsin parafunction and thus cusp anatomyshould reflect this freedom to avoidinterferences. The authors suggested thatocclusal surfaces should reflect a “worst case”scenario as more room for posterior toothmovement in excursions could create noharm.

This brief review of the period 1950–2000recognizes that much of the research wasdevoted to function as well as identifying andrecording the hinge axis, and defining centricrelation (CR). A brief review of the evolutionof CR definitions reveals two major beliefs.The tolerant gnathologists (Ramjford, Wirth,Lauritzon, and Slavicek) recognized thatmuch of the argument of different CRdefinitions was over a less than a .6 mmdifference of condyle position. Gerber andothers argued for a more dogmatic definitionrequiring tripodism of contacts and a pointspecific CR position. (PersonalCommunication – Dr. R. Slavicek July 2010).All gnathologists agreed that a definedreference point was necessary to practiceclinical dentistry.

No review of history would be completewithout emphasizing the contributions of Dr.Harry Lundeen and Dr. Charles Gibbs whocompleted comprehensive research onfunction and dysfunction throughout the60s, 70s, and 80s beginning at Case WesternUniversity and continued after moving to theUniversity of Florida. They preacheddiagnostics as a priority with canine guidanceand 1:2 occlusion ideal.14 In addition, Dr.Robert Lee developed his concept ofbiological occlusion (bioesthetics) during the1960s and 1970s. He was a pioneer in jawtracking and axiopantography and alsorecommended a 1:2 occlusal scheme withcuspid guidance. This concept fit well withthe “tolerant” gnathology as described bySlavicek.

Dental Implants and Occlusion.The unique interface with which implants areintegrated to bone has led to muchconjecture on the best occlusal treatment toensure success. Taylor et al.55 completed anextensive literature review and concludedthat non-axial loading had no effect on theintegrity of the osseointegrated surfacealthough these forces could have a deleteriouseffect on screws and joints. The cylindricalshape, surface coating and threadcomponents of implants make it impossibleto load an implant with just compressiveforces. Tension and shear forces will betransferred to bone at the same time.Progressive loading of implants has beenpromoted as a method of progressivelyincreasing bone mass about implantsthrough graduated application of stress. Theauthors concluded that there was no evidenceto support graduated loading and indeed theconcept was clinically extremely difficult toachieve due to the variety of functional andparafunctional forces involved. Similarly,occlusal overload of implants in animalmodels does not produce a direct cause-effectwith respect to failure of the integration.Finally the authors noted the presence of socalled “osseoperception” that allows properfunctioning of implants without anassociated periodontal ligament. This form ofproprioception comes from the combinedefforts of other stomatognathicproprioceptors.

A second review of occlusal considerations in

TESTER

implant therapy completed by Kim et al.56

emphasized that occlusal overload causesmechanical complications with screws,prosthesis fractures, and implant fractures;however, the effect on integration was notconclusive. They reported that some authorsbelieved that peri-implant bone loss wasprimarily associated with biologiccomplications such as peri-implantitis. Thebasic principles of implant occlusion mayinclude (1) bilateral stability in centricocclusion; (2) evenly distributed occlusalcontacts and force; (3) no interferencesbetween retruded position and centricocclusion; (4) wide freedom in centricocclusion; (5) anterior guidance wherepossible; and (6) smooth, even lateralexcursive movements without working/non-working interferences. The authors discussedvarious occlusal schemes suitable forocclusion on full arch fixed prostheses,overdentures, posterior fixed prostheses, andsingle implant restorations and concludedthat the objectives of implant occlusion wereto minimize overload to the implantprosthesis and interface and to provide longterm stability. This is best accomplished byminimizing force magnification, improvingforce direction and increasing support area.

ConclusionSo where are we today? The dogma of thepast will inevitably be replaced by excellentevidence-based research that can assistclinicians in making proper diagnostic andtreatment decisions. An understanding of thepath that research has taken should lead tobetter experimental designs in the future.Consensus must be established so thatclinical guidelines can be written. A briefreview of the history of “occlusion” is a goodstarting point.

AcknowledgementsThe author gratefully acknowledges thevaluable suggestions offered by Oliver C. PinHarry DDS., graduate resident inprosthodontics, University of North Carolinain the preparation of this manuscript.

References1. 8th edition of glossary of prosthodontic

terms. J Prosthet Dent 2005;94(1). 2. Pokorny P, Wiens JP, and Litvak H.

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historical perspective of the gnathological influence. J Prosthet Dent2008;99:299–313.

3. Becker C, Kaiser D. Evolution of occlusion and occlusal instruments. J Prosthodont 1993;2(1):33–434.

4. Furnace J. In memoriam: Gysi. J ProsthetDent 1958;8(1):5–7.

5. McCollum B, Fundamentals involved inprescribing restorative dental remedies,J Prosthet Dent 1960;10(3):428–35.

6. McCollum SC. A research report. SouthPasadena, CA: Scientific Press; 1955.

7. Sonstebo H., Walker’s improvements ofBonwill’s system. J Prosth Dent 1961;6(11):1074–79.

8. Isaacson D, A clinical study of the Bennett movement. J Prosth Dent 1957;8(4):641–49.

9. International College of Gnathology American Section. Available at: http://www.gnathologyusa.org/History.html.

10. Posselt U. An analyzer for mandibular positions. J Prosthet Dent 1957;7(3):368–74.

11. Posselt U. Registration of the condyle path inclination: Variations using the Gysi technique. J Prosthet Dent 1960;10(2):244–47.

12. Posselt U. Movement areas of the mandible. J Prosthet Dent 1957;7(3):375–85.

13. Woefel J, Hickey J, and Rinear L. Electromyographic evidence supportingthe mandibular hinge axis theory. J Prosth Dent 1957;7(3):361–67.

14. Brotman D. Hinge axes. Part1: the transverse hinge axis. J Prosth Dent; 1960:10:436–40.

15. Jankelson B. Neuromuscular aspects ofOcclusion. Effects of occlusal position on the physiology and dysfunction of the mandibular musculature. Dent ClinNorth Am 1979;157–68.

16. Remien J C, Ash M Jr. Myo-monitor centric: an evaluation. J Prosth Dent 1979;31:137–45.

17. Lundeen H. Mandibular movements recordings and articulator adjustments simplified. Dent Clinics North Am 1979;23(2);231–41.

18. McCollum B. The mandibular hinge axisand a method of locating it. J Prosth Dent 1960;10(3).

19. Møller E. The chewing apparatus. An electromyographic study of the action ofthe muscles of mastication and its correlation to facial morphology. Acta Physiol Scand 1966;69:(Suppl. 280)1–29.

20. Guichet N. Procedures for occlusal treatment, a teaching atlas. Anaheim: Denar Corp.; 1969.

21. Ahlgren J. Mechanism of mastication. Aquantitative cinematographic and electromyographic study of masticatorymovements in children with special reference to occlusion of teeth. Acta Odont Scand 1966;24(Supp):44.

22. Cohen R. The hinge axis and its practicalapplication in the determination of centric relation. J Prosth Dent 1960;10(2):248–57.

23. Naylor J. A scientific concept of temporomandibular articulation. J. Prosthet Dentistry 1962;12(3):476–85.

24. Boucher L. Anatomy of the temporomandibular joint as it pertainsto centric relation. J Prosthet Dent 1962;12(3):464–472.

25. D’Amico A. Functional occlusion of thenatural teeth of man J Prosthet Dent 1961;11(5):899–915.

26. Schuyler C. The function and importance of incisal guidance in oral rehabilitation J Prosthet Dent 1963;13:1011–29. Reprinted: J of Prosthet Dent 2001;86(3):219–32.

27. Lucia V. A technique for recording centric relation. J Prosthet Dent 1964;14:492505.

28. Long J. Locating long centric with a leafgauge. J Prosthet Dent 1973;29:608–10.

29. Williamson E. Leaf gauge technique. Facial Ortho Temporomandib Arthro 1985;2(1):11–14.

30. Jarabak JR. An electromyographic analysis of muscular and temporomandibular joint disturbances due to imbalances in occlusion. Angle Orthod 1956;26:170–99.

31. Lundeen H, Shryok E, and Gibbs C. Anevaluation of mandibular border movements: their character and significance J Prosthet Dent 1978;40:44252.

32. Lundeen H. Mandibular movements recordings and articulator adjustments simplified. Dent Clin North Am 1979;23(2):231–41.




33. Lundeen H, Gibbs C. Jaw movements and forces during chewing. Advances inocclusion. J Prosth Dent 1982;41(1):1–32.

34. Lundeen H. Centric relation records: The effect of muscle action. J Prosth Dent 1974;31:244–51.

35. Weinberg L, Anterior condylar displacement: its diagnosis and treatment. J Prosthet Dent 1975;34:195–207.

36. Williamson E. The effect of bite plane use on terminal hinge axis location. Angle Ortho 1977;47:2533.

37. Dawson P. Centric relation: Chapter 4. Evaluation, diagnosis, and treatment ofocclusal problems. St. Louis: Mosby; 2955.

38. Gilboe D. Centric relation as the treatment position. J Prosthet Dent 1983;50:68589.

39. Lundeen H, Shyrock E, and Gibbs C. Anevaluation of mandibular border movement: Their character and significance J Prosthet Dent 1979;40(4):442–452.

40. McHorris W. Occlusion with particularemphasis on the functional and parafunctional role of anterior teeth Part1. J Clin Orthod 1979;13(9):606–20.

41. McHorris W. Occlusion with particularemphasis on the functional and parafunctional role of anterior teeth Part2. J Clin Orthod 1979;13(10):684–701.

42. Gibbs C, Mahan P. EMG activity of the superior belly of the lateral ptyregoid inrelation to other jaw muscles. J ProsthetDent 1984;51:691–702.

43. Wood DP, Korne PH. Estimated and truehinge axis: A comparison of condylar displacements. Angle Ortho 1992;62(3):167–75.

44. Roth R. Functional occlusion for the orthodontist: Part 1. J Clin Orthod 1981;15:3251.

45. Roth R. Functional occlusion for the orthodontist: Part 2. J Clin Orthod 1981;15:10023.

46. Carr A, Donegan SJ, Christensen LV, andZiebert GJ. An electrognathographic study of aspects of deprogramming of human jaw muscles. J Oral Rehab 1991;18:14348.

47. Kinderknecht K, Wong G, Billy EJ, and Shou Hua Li. The effect of a deprogrammer on the position of the terminal transverse horizontal axis of the mandible. J Prosthet Dent 1992;68:12331.

48. O’Leary TJ Shanley DB, Drake J. J Prosthet Dent 1972;27(1):21–25.

49. Piehslinger E, Celar A, Celar R, Jager W,and Slavicek R. Reproducibility of the condylar reference position. J OrofacialPain 1993;7:68–75.

50. Slavicek R. Clinical and instrumental functional analysis for diagnosis and treatment planning. Part 9: Removable

splint therapy. J Clin Ortho1989;23(2):9097.

51. Weinberg L. Role of condylar position inTMJ dysfunction-pain syndrome. J Prosthet Dent 1979;41:63643.

52. Dawson P. New definition for relating occlusion to varying conditions of the temporomandibular joint. J Prosthet Dent 1995;74(6):619–26.

53. Slavicek R. the masticatory organ: functions and dysfunctions 2002. GAMMA Medizinisch.

54. Wiskott H. and Belser U. A rationale fora simplified occlusal design in restorativedentistry: Historical review and clinicalguidelines J Prosthet Dent 1995;73:169–83.

55. Taylor T, Wiens J, and Carr A. Evidenced-based considerations for removable prosthodontic and dental implant occlusion: A literature review JProsthet Dent 2005;94:555–60.

56. Kim Y, Oh T-J, Misch C, and Wang H-L.Occlusal considerations in implant therapy: clinical guidelines with biomechanical rationale Clin Oral ImplRes 2005;16:26–35.

57. Osborn JW. The temporomandibular ligament and the articular eminence as constraints during jaw openings. J OralRehab 1989;16:323–33.

58. Granger E. The temporomandibular joint in prosthodontics. Prosthet Dent 1960;10(2):239–42.

OCCLUSION


Simplified Muscle Reconditioning Splint Construction:Rationale, Fabrication, and Case Report

Réalisation simplifiée de plaques occlusales pour lereconditionnement de la musculature : principe, fabrication et

rapport de casBy: Dr. Preeti Satheesh Kumar, BDS, MDS; Dr. Satheesh Kumar,BDS,MDS; Dr. Ravindra Savadi, BDS, MDS

About the Authors

Preeti Satheesh Kumar, BDS, MDS, (far left) is an assistant professor in the Department of Prosthodontics, The OxfordDental College & Hospital, Bangalore, India.

Satheesh Kumar, BDS ,MDS, (middle) is an assistant professorin the Department of Prosthodontics, The Oxford Dental Col-lege and Hospital, Bangalore, India. He can be contacted at:[email protected].

Ravindra Savadi, BDS, MDS, (left) is a professor in the Depart-ment of Prosthodontics, The Oxford Dental College & Hospital, Bangalore, India.

ABSTRACTThe management of temporomandibular disorders (TMD) appears to hold an uncommon fascination for clinicians of many disciplines.Any therapeutic approach must be used carefully, for a normalization of the function rather than a pseudo structural ideal.TMD is reversible if caught in time and treated with bite plane therapy in phase I (reversible treatment) and with appropriate phase II therapy(additive or subtractive occlusal therapy, restorative dentistry, orthodontics) to restore balance from/to the CR position. Occlusal splints,which have the advantage of being noninvasive, constitute one of the most therapeutic responses used in the treatment of TMD.

Presented here is an in-office procedure for simplified fabrication of a muscle reconditioning splint/stabilization splint to decrease delayin starting treatment and the time needed for adjustment of the device in the mouth.

RÉSUMÉLe traitement des troubles de l’articulation temporomandibulaire (ATM) semble fasciner les cliniciens de plusieurs disciplines. Touttraitement doit être utilisé avec soin, pour une normalisation de la fonction plutôt que pour un idéal pseudo-structurel. Les troubles del’ATM sont réversibles s’ils sont identifiés à temps et traités par une plaque occlusale à la phase I (traitement réversible) et par untraitement approprié à la phase II (traitement occlusal d’addition ou de soustraction, dentisterie restauratrice, orthodontie) pour rétablirl’équilibre (relation centrée). Les plaques occlusales qui ont l’avantage d’être non invasives constituent l’une des réponses thérapeutiquesutilisées pour le traitement des troubles de l’ATM.


SIMPLIFIED MUSCLE RECONDITIONING SPLINT CONSTRUCTION

The management of temporomandibulardisorders (TMD) is often confusing

because the etiopathogenic phenomenacomplex is multi-factorial. The masticatoryapparatus is not a simple mechanical systembut a complex biological entity, multi-functional, in direct touch with itsenvironment and strongly influenced by theindividual psychosocial aspects. Anytherapeutic approach must be used carefully,for a normalization of the function ratherthan a pseudo structural ideal. Occlusalsplints, which have the advantage of beingnoninvasive, constitute one of the mosttherapeutic responses used in the treatmentof TMD.1,2

This article reports a clinical situation inwhich a combination of physical andodontologic resources followed by oralrehabilitation were used to treat limitedmandibular movements and painfulsymptoms of the muscles of the face.

Clinical ReportA 35-year-old female reported to The OxfordDental College and Hospital with a history ofpain and difficulty in opening the mouthwide. The patient complained of generalizedmuscle soreness in the right side of the face.She had symptoms of pain in the face andears, headaches, and limited functional

mandibular movements. Clinical examinationverified the presence of acute muscular painand tenderness in the right masseter, sterno-cleidomastoid and temporalis muscle, limitedopening, and difficulty in protruding themandible. Intraorally 16, 26, and 46 weremissing, causing drifting and supraeruptionof the adjacent teeth and interferences in themesial and palatal inclines of the mesiobuccalcusp of 27, and the distal and buccal inclinesof distobuccal cusp of 36 resulting in lateralshifting of the mandible from themusculosketally stable position (CR) of thecondyles (Figure 1). The history revealed thatthe symptoms were related to stressfulepisodes at home related to personalproblems.

Here factors related to the development ofTMD include the loss of posterior occlusalsupport, (Angle’s class I) occlusal relation,muscular hyperactivity, emotional stress, andpossibly oral habits.

Treatment PlanThe patient was made aware of therelationship between her emotional stress,parafunctional activity and the symptoms shewas experiencing. Given the clinical findings,this patient was referred to physical therapybefore beginning the odontologicalprocedures. Physical therapy includedcounselling, patient education (habit reversaltechniques and proper use of the jaw), thermotherapy, auto-massage, and stretchingexercises. Behavioural therapy is generallyconsidered as a first conservative approach forthe treatment of TMD patients. The rationalefor choosing behavioural therapy arises fromthe idea that parafunctional activity andpsychosocial factors play a role in thepathogenesis of musculoskeletal pain. Theobjectives of education are to reassure thepatient, to explain the nature, the aetiologyand the prognosis of the problem, to reducerepetitive strain of the masticatory system(e.g., daytime bruxism), to encouragerelaxation and to control the amount of themasticatory activity. Exercise therapy is thecornerstone of rehabilitation of regionalmusculoskeletal disorders. The programsuggested for TMD patients with muscle painand/or limited mouth opening includesrelaxation exercises with diaphragmaticbreathing, auto-massage of the masticatory

muscles, application of moist heat pads on thepainful muscles, stretching, and co-ordinationexercises including proprioceptive trainingand posture.

After the initial physical therapy, specificodontologic procedures began by obtainingmaxillary and mandibular casts, which weremounted on a semi-adjustable articulator anda stabilisation splint was fabricated for nightwear. She was also informed that her occlusalcondition was not stable and might becontributing to her complaints. After allsymptoms had resolved, the significance ofrehabilitating the dentition was discussed.

Rationale of Using a Muscle Reconditioning SplintA Muscle Reconditioning Splint (MRS) is alsocalled the muscle relaxation or stabilizationappliance because it is primarily used toreduce muscle pain and to treat musclehyperactivity. Studies have shown thatwearing it can decrease the parafunctionalactivity that often accompanies periods ofstress. Thus, when a patient has a TMD thatrelates to muscle hyperactivity such asbruxism, a stabilization appliance isconsidered. This appliance can help minimiseforces to damaged tissues, thus permittingmore efficient healing. The treatment goal ofthe stabilization appliance is to eliminate anyorthopedic instability between the occlusalposition and the joint position, thus removingthe instability as the etiologic factor in theTMD.3,4

Allowing the Condyle to Seat in Centric RelationNo report on splints would be completewithout an understanding of the role ofcentric relation (CR) on the healthystomatognathic system. Centric relation is theoptimal arrangement of joint, disk, andmuscle. Splint therapy must use CR as theultimate treatment position. For the condyleto completely seat under the disk in thisanterosuperior position, the lateral pterygoidmust completely relax because of itsattachment to the disk through the superiorbelly. If this muscle stays contracted afterhyperactivity, the disk will be pulledanteromedially (along the direction of themuscle origin) and will not seat completelyover the condyle. When the disk is loaded in aFigure 1. Preoperative intraoral view.

KUMAR ET AL.

power bite or through parafunctionalactivities, the disk, attached muscle, condylarhead, condylar ligaments, and retrodiscaltissues can sustain excess force loads and bedamaged if the condyle/disk assembly is notproperly related to the fossa. Chronic andacute overloading of the condyle/diskassembly when it is out of its normalphysiologic position contributes greatly to thecatch-all term temporomandibular disorder.5

Locating the Musculoskeletally StablePosition/Centric RelationFor muscle relaxation splint to be optimallyeffective, the condyles must be located in theirmost musculoskeletally stable position, whichis centric relation. Two techniques havebecome widely used. The first used thebilateral manual manipulation technique withthe discs properly interposed between thecondyles and the mandibular fossae. In theother technique a stop is placed on theanterior region of the appliance that allowsseparation of the posterior teeth immediatelyprior to centric relation record fabrication.This results in the patient “forgetting”established protective reflexes that arereinforced each time the teeth come together,making mandibular hinge movements easierto reproduce.6–8

Anterior Deprogramming Device FabricationVarious techniques to separate the posteriorteeth include positioning cotton rolls betweenthe incisors, use of a plastic leaf gauge, or asmall anterior deprogramming device madeof autopolymerizing acrylic resin (DPI-RRCold Cure Acrylic Material). The resultinganterior stop acts as a fulcrum, allowing the

directional force provided by the elevatormuscles to seat the condyles in a superiorposition within the fossae.8 The technique isas follows:

1. Clear acrylic resin (DPI-RR Cold CureAcrylic Material) was mixed and adapted tothe maxillary central incisors, ensuringcoverage of the lingual surfaces while foldingit over the incisal edges, slightly extend thematerial onto the facial surface of the teeth(Figure 2). Shape the lingual portion tominimize the amount of contact with themandibular incisors.

2. While it is still soft guide the patient intoclosure until incisal contact occurs on thedevice and the posterior teeth are about 2 mmapart and slight mandibular incisorindentations occur. Cool with an air-waterspray for approximately 10 seconds until thematerial sets hard and confirm that there is noposterior occlusal contact.

3. Trim excess material until there is nointerference during closure .Once the materialhas hardened, using it as a template, a suitablebite registration material (3M ESPE ImprintBite Registration Material Dental Products,D-82229 Seefeld Germany) can be placedbetween the posterior teeth (Figure 3).

How Should an Occlusal Splint be Designed?Maxillary or Mandibular?Presumably it is possible to obtain the sameresults regardless of the situation of theocclusal splint but the choice of the individualsituation of the occlusal splint depends on afew basic principles. It is essential to always

focus on the biggest toothless arch to increasethe stabilizing effect by the creation ofadditional occlusal contact points.1 All teethare in contact in CR on a maxillary appliance.A mandibular appliance often will havecuspid-to-cuspid contact in CR, with themaxillary anterior teeth not touching. Themaxillary appliance is an attractive choice fornight wear, as all of the teeth are in contactwith equal intensity.5 The maxillary applianceis usually more stable and covers more tissue,which makes it more retentive and less likelyto break. It is also more versatile allowingopposing contacts to be achieved in all skeletaland molar relationships. Other reasons for thechoice of one arch over the other include archirregularities, the patient’s profession, and thepotential for gagging.

Should the Occlusal Splint Be Hard orSoft?Since 1942, Mathews recommended the useof soft occlusal splints, which are stillcurrently used.9 However, behind theirsimplicity of utilization, soft splints shownumerous disadvantages. Okeson showedin198710 that the soft occlusal splint couldencourage muscle hyperactivity. Also softocclusal splints deteriorate more quickly bythe simple fact of their nature and it seemsimpossible to equilibrate a soft occlusal splintwhich generates an uncontrolled inter-maxillary relation. The hard occlusal splintthus appears more effective in the reductionof the muscular hyperactivity than the softocclusal splint.1,11

Should the Occlusal Splint Be Complete or Partial?The partial occlusal splint can causeirreversible dental migration (extrusion,intrusion, and laterotrusion) resulting fromthe absence of stabilization with theantagonist arch. For the small pieces, duringsleep the risk of inhalation is not zero. Thefull-arch occlusal splints are thereforerecommended.1

The Occlusal Splint Should Be Smoothor Indented?All splints are classified as eitherpermissive1,5,10 or nonpermissive. A permissivesplint allows the teeth to move on the splintunimpeded, which in turn allows the condylarhead and disk to function anatomically. The


Figure 2. Posterior occlusal contact has beeneliminated while mandibular incisor contactoccurs on anterior deprogramming device.

Figure 3. Centric relation record made withregistration material interposed betweenposterior quadrants while mandibular incisorcontact occurs on anterior deprogrammingdevice.



smooth occlusal splints are represented byanteriorbite splint1 and the smooth full-archocclusal splint by the muscle reconditioningsplint or stabilization splints. A nonpermissivesplint1,5,12 has a ramp or “indentations” thatposition the mandible inferiorly andanteriorly and secure it there. An example ofa nonpermissive splint is anteriorrepositioning appliance.

Historically, treatment of the patient withTMD has been divided into phase I and phase2 therapy. Phase 1 therapy seeks to alleviatepain and improve function and often involvesreversible therapy. This therapy mostcommonly includes physiotherapy,pharmacotherapy (antidepressants), andpsychological therapy (cognitive behaviouraltherapy) and palliative home care. Phase 2therapy involves treatment such as occlusaltherapy (occlusal appliances), surgicalintervention, orthodontic modification, orprosthodontic rehabilitation, and it is oftenirreversible.13 The muscle reconditioningsplint has been indicated in the second placein all cases of persistent TMD despitepreliminary treatment but also in the presenceof acute musculoskeletal pain, significantmalocclusions established and/or majorparafunctions . It is used for its effect on themuscular reconditioning and also to reinforcethe personal responsibility of the patient.1,3,10,14

Therefore it was decided to fabricate a full-arch, hard, permissive maxillary musclereconditioning splint presented here is an in-office procedure for a device to decrease delayin starting treatment and the time needed foradjustment of the device in the mouth.

A face bow transfer is done, next interocclusalrecords are made and the maxillary andmandibular casts are mounted on asemiadjustable articulator in centric relation(see Figure 2 and 3). Undercuts in themaxillary arch are blocked out, and theappliance is developed in wax.

Wax (DPI Modelling Wax) is well adaptedover the teeth on the maxillary cast. While thewax is still warm, close articulator to itsoriginal position established. The thickness ofthe wax will dictate the thickness of thebruxing device.(Figure 4).

The wax must be adjusted in articularreference position (centric relation [CR]),with equal intensity stops on all theantagonistic teeth. The CR represents aposition of reference of mandibular centringin transverse direction ensuring amusculoskeletally stable position for eachcondyle.

Next it must have an anterior guidepermitting the immediate posteriordisocclusion without generating any posteriorinterference Canines must provide a smoothand gentle disocclusion of the posterior teeth.Any contacts on the posterior teeth are causedby eccentric interferences and ought to beremoved. Eccentric contacts of themandibular central and lateral incisors alsomust be eliminated so that the predominantmarks are those of the mandibular canines.During protrusive movement, guidance bythe maxillary canines, not the mandibularcentral and lateral incisors, is the goal.3Wax isadded and or removed wax to achieve this15

(see Figure 4).

Next an occlusal index is made on this waxwith polyvinyl siloxane silicone impressionmaterial (Aquasil Putty and XLV, Dentsply,USA) and the articulator is closed so that theindentations by the mandibular teeth act asan orientation guide (Figure 5).

After applying separating medium to the castand index, the wax is removed from the puttyindex and a mix of clear acrylic resin is loadedinto the putty index until it is approximatelylevel full (Figure 6).Figure 4. Canines provide a smooth and gentle

disocclusion of the posterior teeth.

Figure 5. Putty index is made on this wax, next wax is removed from the index and acrylic resin is loadedinto it.

KUMAR ET AL.

The articulator is closed so that maxillary castis seated in the clear acrylic resin (DPI -RRCold Cure Acrylic Material). The twomembers of the articulator are lockedcarefully and the resin is allowed to set. Afterwhich it is trimmed and polished and checkedin the patients mouth (Figure 7 and Figure 8).

Instructions and AdjustmentsThe patient is instructed to use the applianceat night. She is monitored at regular intervals.As muscles relax and symptoms resolve, asuperoanterior position of the condyle may beassumed. This change must be accompaniedby adjustments of the appliance to optimumfunctional occlusion. Wearing must not

exceed a few months because, with herparafunctional habits, the patient gets used tothe occlusal splint and a negative dependencecan be created. So that the patient is awarethat her TMD is correlated with stressfulsituations such as her children’s examinationsor sporting events, episodic daytime wearingmay be advisable during these periods orduring activities.

DiscussionIf a patient rapidly becomes comfortable witha splint, it may be an indication that thedisorder is muscular. If symptoms worsenwith permissive splint wear, this may indicatean internal derangement (disk) problem or anerror in the initial diagnosis. In and of itself,this information has limitations. However,with a thorough TMD and occlusalexamination, such information can be aninvaluable piece of the diagnostic puzzle.5

The stabilization splint or the musclereconditioning splint does not cure thepatient, but could improve during sleep, theunconscious behaviour. It protects thestructures and perhaps re-educates musclesand joints.1 But especially, when it is necessary,it reinforces the personal implication of thepatient, which is, in fact, the essentialtreatment. The wearing should be precededfor about 1 or 2 months of treatment withbehavioural rehabilitation (emotional stresstherapy) only to induce the patientawareness.16 Behavioural therapy is generallyconsidered as a first conservative approach forthe treatment of TMD patients. Apsychotherapist can help the patient deal withthese extreme stressful conditions butultimately patients do best when clinicianstake the time to fully inform them about theircondition. This contributes to reduce the fear,the depression and the anxiety that arecharacteristic of chronic pain patients. Thismeans that enforcing patient responsibilitiesand thereby addressing psychosocial factors(like coping and locus of control) can be apowerful tool for successful rehabilitation.16

The patient has to be reassured by explainingthe problem, the supposed etiology and thegood prognosis of this benign disorder.Patients require good information to assistthem in making choices, overcomingunhelpful beliefs, and modifying behaviour.

The relationship between chronic pain andpsychosocial distress should also be stressed.The rationale for choosing behaviouraltherapy arises from the idea thatparafunctional activity and psychosocialfactors play an important role in thepathogenesis of musculoskeletal pain.16–19

Normal jaw muscle function has to beexplained, stressing to avoid overloading ofthe masticatory system, which could be themajor cause of the complaints. The patientshave to pay close attention to the jaw muscleactivity, to avoid bad oral habits and excessivemandibular movements. In acute conditions,they have to avoid hard food and/or cut hardand tough food in small pieces, chew withback teeth on both sides, and avoid chewinggum. Later in the rehabilitation programtraining of restrictive activities of daily livingis part of the procedure in order to return tonormal, or desired, levels of activity andparticipation, and to prevent the developmentof chronic complaints. Behaviourmodification strategies such as habit reversalare commonly used. Although many habitsare abandoned when the patients becomeaware of them, changing persistent habitsrequires a structured program. Patientsshould be aware that habits do not changespontaneously and that they are responsiblefor the change.16

Advantages regarding tooth replacement werediscussed and the patient elected to accept thetreatment. Permanent alteration of theocclusal condition is indicated for tworeasons. The first and most common being toimprove the functional relationship betweenmaxillary and mandibular teeth and thesecond may be as a treatment goal toeliminate TMD. Here the patient had missingteeth which caused orthopedic instability.Therefore the occlusal interferences wereeliminated first. If occlusal prematurities existin the preoperative situation and typicalsimple-to-complex restorative procedures areaccomplished without removal of occlusalprematurities, the new restorations mayincrease occlusal disharmonies andsubsequent occlusal problems. An analogy isa dirt road with deep ruts in it. Driving out ofthe ruts is difficult or sometimes impossible.20-22

Similarly, if occlusal prematurities are presentin the preoperative state, the new restorationsmust adapt to the incorrect occlusion, and any


Figure 6. Stabilization splint realized at themaxillary arch.

Figure 7a. Left laterotrusive movement guided bythe left maxillary canine.

Figure 7b. Right laterotrusive movement guided bythe right maxillary canine.



subsequent attempts at occlusal equilibrationare more difficult.20 Wearing of thestabilization splint and subsequentimprovement of the condition was significantevidence to support that the occlusalcondition was the causative factor related toTMD. Restoration of posterior teeth has beensuggested to decrease or eliminate the painassociated with TMDs. The patient wasrehabilitated with metal ceramic restorationsand has been symptom free following theocclusal therapy (Figure 8). The treatmenteffect has been attributed to stabilization ofthe occlusion, redistribution of occlusalforces, and reduction of joint loading.21

ConclusionTo conclude, the occlusal splint fabrication is,today, an act proposed mainly as a second-phase of treatment after a first initialtreatment phase: psychotherapy, behaviouraleducation, physiotherapy, and homeexercises.1 The clinician is faced with the needto provide therapy that has some reasonabledegree of objective and/or subjective impacton the effects of a disorder. The therapyshould do no harm; be acceptable in terms ofpatient’s criteria for success; be in keepingwith the need to balance costs, benefits, andrisks; and be consistent with the standard ofcare determined by the dental profession.

From the standpoint of clinical reality, theeffects of occlusal equilibration on functionand parafunction is one of the majortreatments for occlusally oriented diseases.The occlusal splint is, mainly, a means ofreinforcing the auto-management of thepatient; it offers him the opportunity tocontrol dysfunctions by himself. But thepractitioner must imperatively explain the useof the occlusal splint installation, because it isessential that the patient understands theprinciple and its implications on thetreatment.

DisclosureNo conflicts declared.References1. Ré JP, Perez C, Darmouni1 L., et al. The

occlusal splint therapy J Stomat Occ Med2009;2:82–86.

2. Gray RJ, Davies SJ Occlusal splints and temporomandibular disorders: why, when, how? Dent Update 2001;28(4):194–99.

3. Okeson JP. Management of temporamandibular disorders and occlusion, 6th Edition. New York; Moseby Yearbook Inc. 1998, 468–94.

4. Yap AU Effects of stabilization applianceson nocturnal parafunctional activities inpatients with and without signs of temporomandibular disorders. J Oral Rehabil 1998;25(1):64–8.

5. Dylina TJ. A common-sense approach tosplint therapy J Prosthet Dent 2001;86:539–45.

6. Urstein M, Fitzig S, Moskona D, CardashHS. A clinical evaluation of materials used in registering interjaw relationships.J Prosthet Dent 1991;65:372–77.

7. Hunter BD II, Toth RW. Centric relationregistration using an anterior deprogrammer in dentate patients. J Prosthodont 1999;8:59–61.

8. Land MF, Peregrina A. Anterior deprogramming device fabrication usinga thermoplastic material J Prosthet Dent2003;90:608–10.

9. Wright EF. Using soft splints in your dental practice. Gen Dent 1999;47:506–10.

11. Okesson JP. The effects of hard and soft occlusal splint on nocturnal bruxism. J Am Dent Assoc 1987;114:788–91.

12. Turp JC, Komine F, Hugger A. Efficacy of

stabilization splints for the managementof patients with masticatory muscle pain:a qualitative systematic rewiew. Clin OralInvestig 2004;8:179–95.

13. Dawson P. Evaluation, diagnosis and treatment of occlusal problems. 2nd ed. St. Louis: Mosby; 1989. 183–205.

14. Temporomandibular Disorder Prosthodontics: Treatment and Management Goals Report of the Committee on Temporomandiular disorders of the Am Coll Prosthodont J Prosthodont 1995;4(1):58–64.

15. von Krammer RK. Constructing occlusal splints J Prosthet Dent 1979;41:105–108.

16. Austin D and Attansio R. Procedure for making a bruxism device in the office. J Prosthet Dent 1991;66: 266–69.

17. Michelotti A, Steenks D, and Farella M.Home-exercise regimes for the management of non-specific Temporomandibular disorders J Oral Rehabil 2005;32;779–85.

18. Stohler CS, Zarb GA. On the management of temporomandibular disorders: a plea for a low-tech, high-prudence therapeutic approach. J OrofacPain 1999;13:255–61.

19. Michelotti A, Steenks MH, Farella M, et al. The additional value of a home physical therapy regimen versus patient education only for the treatment of myofascial pain of the jaw muscles: short-term results of a randomized clinical trial. J Orofac Pain 2004;18:114–25.

20. Okeson JP, Hayes DK. Long-term resultsof treatment for temporomandibular disorders: an evaluation by patients.J AmDent Assoc 1986;112:473–78.

21. Christensen G. The major part of dentistry you may be neglecting JADA 2005;136(4)497–99.

22. Tallents RH, Macher DJ, Kyrkanides S, etal. Prevalence of missing posterior teethand intraarticular temporomandibular disorders J Prosthet Dent 2002;87:45–50.

Figure 8. Completed prosthesis.


An abnormally small oral orifice is definedas microstomia.1 It may result from

surgical treatment of orofacial neoplasm, cleftlip, maxillofacial trauma, burns, Plummer-Vinson syndrome, scleroderma, radiotherapy,or certain systemic and developmentaldiseases.2,3 Conservative management ofmicrostomia has been described in literatureand includes the use of microstomia orthosesto expand the oral opening.4,5 Prosthodontictreatment, however, is more complex due toreduced oral opening. Making the impression

represents the initial difficulty in prostheticrehabilitation.

Luebke described a sectional impressionprocedure for dentulous patients by using twoplastic sectional impression trays assembledwith Lego building blocks and autopolymerizing resin.6 Whitsitt and Battleintroduced a procedure for obtaining theprimary impression of edentulous arches usingputty silicone as flexible tray then washingwith light-body silicone to obtain more detail.7

Heasman et al. modified a procedure formaking final impressions of edentulous archby using two sectional acrylic resin impressiontrays joined together with two fins.4

Moghadam advocated a practical procedure toobtain maxillary primary casts of edentulouspatients. Two identical perforated stock traysare cut symmetrically, leaving their ownhandles attached. The trays are cut minimallyin width to allow their insertion into oralcavity with ease.7 McCord et al. described asimplified technique for joining the final

CLINICAL FORUM / FORUM CLINIQUE

Simplified Impression Procedure for A Patient with MicrostomiaUne empreinte simplifiée pour un patient avec microstomie

By Dr. Praveen G, MDS; Dr. Swatantra Agarwal, MDS; Samarth Agarwal, MDS; Saurabh Gupta, MDSc; Atul Bhardwaj, post-graduate student.

About the Authors

Dr. Praveen G., Dr. Swatantra Agarwal, Samarth Agarwal, Saurabh Gupta, and Atul Bhardwaj are all with the Department of Prosthodontics; Kothiwal Dental College and Research Centre, Moradabad, Uttar Pradesh, India.

ABSTRACTMicrostomia may result from surgical treatment of orofacial neoplasms, cleft lip, maxillofacial trauma, burns, Plummer-Vinson syndrome,scleroderma, radiotherapy, or certain systemic and developmental diseases. Making the impression represents the initial difficulty inprosthetic rehabilitation of such patients because of the abnormally small oral orifice. Sectional impression trays for both the primaryand final impression of maxillary edentulous arches where microstomia exists have been introduced by other authors. This article pres-ents a simplified impression procedure for obtaining an accurate impression by modification of sectional plastic stock trays to obtaina single full arch impression.

RÉSUMÉLa microstomie peut être le résultat d’une chirurgie de néoplasmes de la sphère orofaciale, de becs-de-lièvre, de traumatisme maxillo-facial, de brûlures, du syndrome de Plummer Vinson, d’une sclérodermie, de radiothérapie ou de certaines maladies systémiques etd’anomalies du développement. L’orifice buccal anormalement petit de ces patients rend la prise d’empreinte difficile. Les porte-empreinte par sections pour la première empreinte et l’empreinte finale des arches édentées du maxillaire en présence de microstomieont été introduits par d’autres auteurs. Cet article présente une prise d’empreinte simplifiée pour obtenir une empreinte exacte enmodifiant les porte-empreinte par sections en plastique pour une empreinte de l’arche au complet.


A SIMPLIFIED IMPRESSION PROCEDURE FOR A PATIENT WITH MICROSTOMIA

impression by using a sectional tray in whichone section locks into other section in keyedrecess.8 Baker et al. used sectional lockingcustom trays for making an accurateimpression.9 Al-Hadi describes a three-section tray for a preliminary impression anda final impression10 followed again by a two-section tray to make more accurate finalimpression.

This article describes a simplified impressionprocedure for obtaining an accurate impressionby modification of sectional plastic stock traysto obtain a single full arch impression fordentulous microstomic patients.

Technique Two perforated sectional stock trays, rightand left side are selected (Figure 1). The rightside tray is checked for buccal and lingualextensions, then the tray is trimmed andadjusted (Figure 2). This tray will record theimpression of the dentulous area on theentire right side along with the anterior teethon the contralateral side. A trough is made onthe external surface of the handle on this tray. The left-side tray is checked for buccal and

lingual extensions. The labial and lingualflanges in the tray are trimmed, but only inthe anterior region without trimming theocclusal surface (Figure 2). The impressionmade in this tray will overlap the right-sidetray only in the anterior region and willrecord the posterior dentulous area of theentire left side. Nick and notch is made on thetissue surface of the handle on this tray. Thehandle of this tray is then lubricated withpetroleum jelly.

A green tracing stick is softened over a flameand placed in the trough made on the handleof the right-side tray. Before the green tracingstick hardens, both the trays are placed intra-orally, oriented together, and stabilized untilthe green tracing material hardens (Figure 3).Green tracing material in the trough of theright tray will record the nick and notchmade on the tissue surface of the handle onthe left tray (Figure 4). This record helps toorient the trays during and after theimpression, enabling the registration of a fullarch single impression.

Alginate is mixed according to the

manufacturer’s instruction and loaded on theright-side tray, placed in the mouth andstabilized till the material sets. This tray iskept in mouth undisturbed till the entire archimpression is completed (Figure 5). Theimpression made in this tray will record thedentulous area of the entire right side alongwith the anterior teeth on the other side.

Alginate is again mixed and loaded on the leftside tray, placed in the mouth and orientedaccurately with the help of nick and notchthat is recorded by the trough and stabilizedtill the alginate sets (Figure 6). Theimpression made in this tray will overlap theright side tray only in the anterior region andwill record the posterior dentulous area of theentire left side.

After the impression material sets, the lefttray is removed first and then the right tray isremoved (Figure 7). Both of the impressionsare washed to remove any salivary debris, aredisinfected, and are then oriented accuratelywith the nick and notch extra-orally to obtaina single full-arch impression (Figure 8).

Figure 1. Selected right and left sectional stocktrays.

Figure 4. Nick and notch made on the handlerecorded by trough with a green tracing stick.

Figure 2. Modified flanges of right and leftsectional stock trays.

Figure 5. Right-side tray loaded with alginate andplaced intra-orally.

Figure 3. Tray positioned intra-orally and stabilizedfor recording nick and notch.

Figure 6. Left-side tray loaded with alginate placedintra-orally, oriented accurately to right tray bynick and notch and stabilized until alginate sets.

PRAVEEN G. ET AL.

DiscussionThe rehabilitation of a patient suffering frommicrostomia is challenging to a prosthodontistbecause of the patient’s clinical condition. Thiscondition often complicates and compromisesthe prosthodontic treatment plan. For suchpatients, a prosthodontist encounters certainproblems during treatment such as: difficultyin insertion of full-size stock trays, trauma toperi-oral tissue due to lack of flexibility of oraltissue, and improper tissue manipulation dueto fibrous bands.

A modification of conventional impressionprocedure is therefore required for recording

an accurate impression. The approach toimpression making have been numerous andthe literature describes a number of sectionalimpression techniques using split custommade impression tray for both primary andsecondary impression. Various pins, bolts,and Lego pieces have been used for thelocking mechanism of sectional impressiontrays fabricated for patients with limited oralopening.3,6,11

The technique described here is simplifiedand cost-effective as compared to Leubkesmethod by utilizing Lego plastic buildingblock for joining the two halves. The materialused in this technique is easily available.

Less time is required for modification ofsectional plastic stock trays as compared toBakers technique in which additional timeand labour was required for customfabrication of a sectional tray. Also, with thistechnique, tray manipulation and impressionmaking is simpler, as compared to the Al-Hadi technique in which three sections oftrays were made for preliminary impressionand final impression. With this proposedtechnique, the buccal mucosa is nottraumatized and the patient is comfortablewhile utilizing less chair-side time.

ConclusionImpressions can be made for patients withreduced mouth opening with a sectionalimpression tray that can be assembled anddisassembled in the mouth and thenreassembled outside the mouth. This articledescribes an impression technique forpatients with limited mouth opening, usingsectional impression trays to obtain full archimpression.


References1. Academy of Prosthodontic. The Glossary

of prosthodontics terms. 8th ed. J Prosthet Dent 2005;94:10–92.

2. Whitsitt JA, Battle LW. Technique for making flexible impression trays for themicrostomic patient. J Prosthet Dent 1984;52:608–9.

3. Cura C, Cotert HS, User A. Fabrication of a sectional impression tray and sectional complete denture for a patientwith microstomia and trismus. a clinicalreport. J Prosthet Dent 2003;89:540–43.

4. Heasman PA, Thomason JM, Robinson JG. The provision of prostheses for patients with severe limitation in opening of the mouth. Br Dent J 1994;26;171–74.

5. Benetti R, Zupi A, Toffanin A. Prostheticrehabilitation for a patient with microstomia: A clinical report. J ProsthetDent 2004;91:322–7.

6. Luebke RJ. Sectional impression tray forpatients with constricted oral opening. JProsthet Dent 1984;52:135–37.

7. Moghadam BK. Preliminary impressionin patients with microstomia. J ProsthetDent 1992;67:23–5.

8. McCord JF, Tyson KW, Blair IS. A sectional complete denture for a patientwith microstomia. J Prosthet Dent 1989;61:645–47.

9. Baker PS, Brandt RL, Boyajian G. Impression procedure for patients with severely limited mouth opening. J Prosthet Dent 2000;84:241–44.

10. AL-Hadi LA, Abbas H. Treatment of edentulous patient with surgically induced microstomia: A clinical report. J Prosthet Dent 2002;87:473–76.

11. Dhanasomboon S, Kiatsiriroj K. Impression procedure for a progressive sclerosis patient: A clinical report. J Prosthet Dent 2000;83:279–82.


Figure 7. Disassembled impression of right and leftside removed.

Figure 8. Left- and right-side impressionsassembled extra-orally to obtain a single full-archimpression.

iPad advances digital dentistry.When new patients enter Dr. JonathanFerencz’s thriving prosthodontics practice inmidtown Manhattan, they’re greeted with asmile – and an iPad.

For Dr. Ferencz, the latest technology hasalways driven quality patient care. As an earlyiPad adopter, Dr. Ferencz knew the devicecould launch a new era in digital dentistry.

iPad has become central to all aspects of thepractice. In addition to simplifying patientforms and record-keeping, iPad enables Dr. Ferencz to show his clients photos oftreatment options. And his technicians refer todigital images on iPad to create perfect-lookingdental prosthetics.

Painless Patient RecordsiPad simplifies the record-keeping process forboth patients and staff. Rather than designing,filling out, scanning, and then shredding paperforms, Dr. Ferencz and his staff have created afast, efficient system using iPad.

Patients complete their intake forms directlyon iPad using the Adobe Ideas app, and caneven sign the form using a stylus on the iPadscreen. From there, a member of his staffemails the forms into the practice’s database.There’s no paper and nothing to file. “It’sefficient,” Dr. Ferencz says. “With iPad, we saveso much time – and space.”

Putting iPad into patients’ hands also helpsemphasize Dr. Ferencz’s commitment to thelatest and best dental practices. “It conveys asubliminal message that this office is up-to-date technologically,” he says. “So they knowthat we’re up-to-date in our dentistry as well.”

Visual ConversationsWhen patients enter the treatment room, iPadtakes on another role: communication tool.

Prosthodontics deals with aesthetic andreconstructive dentistry, such as crowns andveneers. Dr. Ferencz’s challenge is to getpatients to see what he sees, and to show themwhat he can do. With iPad, he can effortlesslydisplay photographs and radiographs topatients during consultations. And using theAdobe Ideas app, he can annotate the imagesonscreen while pointing out areas of interest.

“iPad is ideally suited to this kind of visualconversation,” he says. “The patient and I canflip through the radiographs and clinicalphotos together, and I can illustrate my pointsas we go.”

Because the patient has a visual idea of theprocedure and a sense of what the outcomewill look like, the result is a directimprovement in care. “With iPad, I can greatlyenhance patient acceptance of my proposedtreatment,” Dr. Ferencz says.

iPad in the LabDr. Ferencz’s iPad use doesn’t end inthe treatment room. Immediately aftera discussion with a patient using iPad, Dr. Ferencz might bring the device tohis in-house lab to demonstrate anissue to one of his technicians.

“On a dental restoration, the mosteffective way to make a correction is toshow the photograph to my technicianand say, ‘Here’s how I’d like you toreshape it,’” he says. “That way, we’rehaving a conversation about a clinicalphotograph, not a drawing or adiagram.”

A Business of TrustiPad is also a powerful, persuasive wayto share images during doctor-patientconversations about treatment options.“On our first day with iPad, I used it

three times to show patients radiographs and photographs of clinical conditions,” Dr. Ferencz explains. “And in each case thepatient booked the procedure immediately.”

When he asked the patients whether thepresentation on iPad had an impact on theirdecisions, one of them said, “I trust Dr. Ferencz, and I would have done what hesaid, but the way the images appeared was justamazing. I had to schedule the procedureimmediately.”

And this is just the beginning. “I think we’vejust begun to scratch the surface with iPadapplications,” he says. “It really is totallyrevolutionary.”

http://www.apple.com/ipad/business/

INDUSTRY NEWS


iPad in Business

“With its high resolution and ease of use, iPad has the ability to make a major impact on oral health care.”

Jonathan L. Ferencz, D.D.S.NYC Prosthodontics

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Occlusion Dr. Harry Rosen: Dentist and Sculptor/Dentiste et sculpteur