RCPO Functional

155Clin. Pesq. Odontol., Curitiba, v.2, n.2, p. 155-163, out/dez. 2005

Contribuição especial Functional occlusion and orthodontics: a contemporary approach

FUNCTIONAL OCCLUSION AND ORTHODONTICS:A CONTEMPORARY APPROACH

Oclusão funcional e ortodontia: uma abordagem contemporânea

Marco A. L. Feres 1

Marines Q. Portella 2

Renata C. L. Feres 3

AbstractThe authors have undertaken a deep review on funcional occlusion, from historical to contemporaryconcepts. Also the interrelationship between occlusion and orthodontic treatment was described, proposingobjectives that should be achieved to establish good harmony with the stomatognatic system.Keywords: Functional occlusion; Orthodontics; Treatment goals.

ResumoO primeiro objetivo deste trabalho foi realizar uma revisão de literatura sobre oclusão estática e dinâmica,revisando desde conceitos históricos até os conceitos mais aceitos atualmente. O segundo objetivo foi unirestes conceitos com o tratamento ortodôntico, definindo, a partir daí, como o ortodontista deve tratar seuscasos, assegurando a harmonia de todo o aparelho estomatognático.Palavras-chave: Oclusão funcional; Ortodontia; Objetivos de tratamento.

1 Professor Adjunto, Disciplina de Oclusão, PUCPR; Disciplina de Ortodontia, UFPR; Título de Notório Saber em Ortodontia, UFPR. Endereço: Rua Imaculada Conceição, 1.155 - Prado Velho - Curitiba, PR2 Especialista em Ortodontia; Mestre em Morfologia Aplicada/DTM3 Mestre em Ortodontia.

156 Clin. Pesq. Odontol., Curitiba, v.2, n.2, p. 155-163, out/dez. 2005

Marco A. L. Feres; Marines Q. Portella; Renata C. L. Feres

Evolution of a concept

The word “occlusion” comes from the la-tin expression occludere which means “ to close”.According to Galvão (1) this term is related to theestatic or dynamic arrangements that exist betwe-en opposed teeth. Occlusion also means the func-tional relationships of all components of the mas-tigatory system, such as bone, TMJ, muscles andsupporting tissues.

Other authors (2,3) state that the initialconcept of occlusion was related to fixed relationsof the jaws, but a correct analysis has to take intoconsideration all tissues involved, including theTMJ, as well as all stimuli that derives from theoclusal contacts like curve of Spee, cusps height,condilar guidance and the occlusal plane.

Primary studies on occlusion include thearea of prosthodontics (4, 31) because early speci-alists needed to know how teeth should get incontact. Therefore the development of the con-cepts of occlusion are directed related to the evo-lution of articulators. Since Phillip Pfaff in Germanyin 1756 (1) has “registered the bite” thus obtainingplaster models, many other pioneers studied den-tal contacts through the use of articulators (4,5),including parameters to the position of the condy-les into the fossae and the concept of “balancedocclusion” .

As time occurred, some of early conceptsbecame tested principles thus originating philoso-phies, the main ones consisting of the “balance”and the “non-balanced” occlusion. The first follo-wed principles of Bonwill (5),Monson (6), Wa-dsworth (7), Gysi(8) and others, and its main foun-dation included multiple contacts of opposing tee-th both in centric as well as excentric mandibularmovements.

In 1926 a new and organized school ofocclusion was criated, the Gnatological Society ofCalifórnia (9, 10), defining gnatology as the scien-ce that treats the biology of the masticatory “appa-ratus” . This masticatory system should be consi-dered as a functional unit, thus providing: 1. thecoincidence between centric relation (CR) and cen-tric occlusion (CO); 2. a well balanced occlusionduring slidind movements, with bilateral multiplebalanced contacts (11).

In 1950 (12), opposed to the “gnatologi-cal principle”, eroded the concept of the “longcentric” (12), which would mean freedom of man-

dibular closure, both in CR or CO, consisting onthe Pankey-Mann Philosophy of Occlusal Reabili-tation.

Ramjord and Ash (13) proposed the “func-tional occlusion” approach meaning an individualattention to the demands of each patient, empha-sizing the health of the masticatory system overany specific occlusal configuration.

Dawson (14) stablished criteria for an idealocclusion running from selective grinding to com-plete occlusal reconstruction. He recommendeddisoclusion in the balance side as well as groupfunction in the working side.

“Normal” and “ideal” occlusion

Normal occlusion has referenced diag-nosis and treatment planning in Orthodontics,but many times this concept has been misun-derstood with ideal occlusion. This late aspect isseldom seen, thus Profit and Ackermann (15)prefer the term “imaginary ideal” meaning theone that provides all physiological functions ofthe masticatory system while preserving the he-alth of all structures related. According to Ashand Ramjord (17), the perfect idea of 138 occlu-sal contacts of all 32 teeh is rarely founded. Inother study (18) the same authors state that theconcept of normality in any biological systempresupposes a physiological “break” for adapta-tion around those values that are considerednormal.

Angle (19) has set the normal occlusi-on conditions with emphasis on the first molarrelationship, stating that the mesiobuccal cuspof the upper first molars should occlude on theocclusobuccal groove of the lower first molars.Graber (20) and Moyers(21) stated that normalocclusion includes oclusal contacts, teeth align-ment and good relationship to the bony structu-res.

Beyron (22) refers to ideal or optimumincluding function, health and confort, not onlyesthetics and anatomy.

When summarizing most author’s opi-nions we come o the conclusion that an “ideal”occlusion shall pursuit :

• neuromuscular harmony• oclusal stability

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• health periodontium• accepted esthetics• good masticatory function• normal phonetics• absence of parafunctional habits• no TMJ pathological evidence• oclusal loads distributed along the ver-

tical axis of teeth.• adequate anterior guidance• good bilateral balance• minimum muscular tension plus ma-

ximum efficiency.• minimum dental wearing

During all functions of the masticatorysystem, the mandible assumes a variety of posi-tions from centric to excentric movements. Inorder to analyse all the aspects involved weshould consider occlusion from maximum inter-cuspation to all mandibular movements.

Maximum Intercuspal Position (MIP)

According to Lee (23) this position isreached over 5000 times a day during the mas-ticatory cycle, with occlusal forces varing in-dividually. Okeson (24) states that total forceloaded daily during chewing and deglutitionmay reach 8600 kg, decreasing at night.

Orthlieb e Laplanche (25) describesMIP as the oclusal position with the greatestinterarches contacts with maximum intensityof isometric contractions. It is important to em-phasize that such independs on the positionof the condyles into the glenoid fossae.

Ash and Ramjord (17) describes MIPas a tooth to tooth relationship, guided by itsocclusal surfaces. This position may vary ac-cording to changes in these oclusal surfaces.The same authors refer to MIP as “intercus-pal”,” dental”, “acquired centric” or simply“habitual centric”. It is important to emphasi-ze that the expression Centric Occlusion (CO)became elected in the literature when refer-ring to MIP.

Authors (25) focus on the fact that allteeth should participate of these contacts, whilefailure in achieving so may be caused by mus-cular habits, eruption problems of skeletal im-balance.

Centric Relation (CR)

It is a key reference to analyse andreconstruct the masticatory system. It is aposition that is achieved when the operatortakes the condyles and disc to the anteriorwall of the fossae. Such position is disc ori-ented and is a very useful reference to che-ck or modify interarches relationships.

According to Ash (17) MIP rarely co-incides with CR. For some authors (16,26,27)the best condyle-fossa relationship is theone achived in CR . During many years, RCwas describe as the most retruded positionof the mandible, from which lateral move-ments could be undertaken (28, 29, 30, 31).

After laminagraph studies (32) thisconcept changed dramactically, with outli-ned condyles well seated into the fossae.Later on, Dawson (33) defined CR as theupper position that could be reached by yhecondyles into the mandibular fossae.

Eletromiografical studies (34, 35) re-lated that the physiological position of thecondyles, determined by musculature, is su-perior and anterior, against the posterior slo-pe of the articular eminence. Okeson (37)refers to the ideal position of the condyleinto the fossae as “orthopedic stability ofthe mandible” or “muscular – skeletal stabi-lity” .

Authors (38) founded great stabilityin condyles when in this upper/anterior po-sition, in close contact with the disc. Underthese circunstances, the compression forcesproduced by muscles are well tolerated oncethe disc is basically formed by dense cola-genous tissue with no innervation or irriga-tion in the central zone. On the other hand,continuos forced derived to other areas ofthe disc may result in damage of the tissu-es involved.

Masticatory forces should be distri-buted along the vertical axis of teeth, thusbeing well tolerated by all periodontal tis-sues while involving a maximum number ofhorizontal and oblique fibers. Through thisapproach the impact of masticatory loads isuniformed distributed along all supportingtissues. (22,18)

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Mandibular movements

During ideal mandibular movements twofactors are of umost importance : freedom of mo-vement and “economy” of muscular energy. Theseconditions are provided by anterior guidance inprotrusive movements and by canine protectionor group function in lateral excursions.

According to Fantini (39) one mustdifferenciate total from partial group function, thelatest meaning that not all teeth in the workingside are involved with the disoclusion process.Neverthless, many patients include only the cani-nes and bicuspids in such gnatological approach.

In “ideal” occlusions anterior guidanceorients mandibular movements and shall be ableto provide MIP without articular or neuromuscularaccommodation, which by all means represents“economy” in muscular energy .

According to Kahn (40), canine guidanceis the main mechanism to disoclude posterior teehfrom the working side. On the other hand, the keyfactor for disoclusion in the balance side is thesliding movement of the condyle through the pos-terior slope of the articular eminence. The canineprotected occlusion concept (41,42,43) is basedupon the fact that the canine tooth is the mostappropriate element to guide mandibular lateralexcursion due to crown morphology, root andperiodontal strength plus superior proprioceptivemechanism.

Other authors (44) did some eletromio-grafical studies on elevator muscles relating themto group function or canine protection. Resultsdemonstrated in group function there was a clearreduction in muscle action when compared to in-tercuspal position, mainly to the temporal musclefrom the balance side. When analyzing canine pro-tected occlusions, reduction in muscle activity wasgreater than in group function.

According to Lee (23) canine guidance isoptimum to :

• avoid excentric lateral interferences ofposterior teeth.

• provide freedom of condilar move-ments.

• orient mandibular closure in a morevertical pattern.

According to Roth (35), incisal guidan-ce should be established by all six upper and

eight lower anterior teeth, thus dividing protrusi-ve load. Smooth anterior guidance are vital notonly to appropriate function during mandibularexcursions but are strongly related to occlusal sta-bility after orthodontic treatment. He stresses thatexcessive lateral load on the canines may result inlingual movement of the lower cuspids with sub-sequential anterior crowding.

Ideal occlusion and orthodontics

Proper adaptation of all concepts of opti-mun occlusion into modern orthodontic therapydemands basic atitudes related to diagnosis, treat-ment planning, mechanics, finishing and retenti-on. As widely known, orthodontic treatment hasa very close relationship with all components ofthe masticatory system, therefore the specialistneeds to be expertise in all aspects of functionalocclusion. The Angle’s classification is a good wayto start with, but in no way offers adequate para-meters for defining treatment goals. Many occlusi-ons presenting solid class I relationship may pre-sent several pathological aspects.

In order to achieve proper parameters,Andrews (46) studied positions and interarch rela-tionships of all crowns of 120 models presenting“optimum” occlusions, which he called “The SixKeys to Normal Occlusion” . His method allowsone to assess all pertinent aspects of the occlusionfrom the labial and occlusal surfaces. These sixkeys are :

• 1 – Anteroposterior relationship• 2 – Crown angulation• 3 – Crown inclination.• 4 – No rotations• 5 – Solid interproximal contacts• 6 – Presence of Curve of Spee.

Yet according to Andrews (46), the sixkeys are independent elements of the structuralsystem and consist in solid foundation for occlusalassesment and treatment goals for most patients.

The modern concept of occlusion in or-thodontics includes all TMJ components (49). Be-fore aplliances removal it is essential to observemandibular movements and check for interferen-ces. Testing the working side with canine guidan-ce or group function thus providing no contacts in



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the balance side, as well as smooth anterior con-tacts in protrusive is of utmost importance to achie-ve good functional occlusion (50).

Case presentation

A15-year-old oriental boy was referred byhis general dentist for evaluation of crowding, ar-

chform assimetry, anterior aesthetics and some di-fficulty in chewing. There was no significant me-dical history. His oral hygiene was good and hehad received routine dental care since early chil-dhood. Despite presenting some interferences nosignificant signs or symptoms of temporomandi-bular joint were related.

Fig. 1 – Pre treatment photographs

Fig. 2 – Pre treatment models

Diagnostic and etiology

The patient showed a harmonic andsimetric face both from frontal and lateral,with a slight convex profile. The occlusal re-lationship presented a Class I molar relati-onship, deep overbite, crowding in the inci-sal area . The upper arch showed a constric-ted “V” shape, with midline deviation to theleft. The following occlusal problems werelisted :

a) Too long and deep incisal guidance,thus leading to an excessive anterior condilar dis-placement in protrusive; b) Contacts on the upper

lateral incisors in working side; c) Some interfe-rences in the balance side, right and left.

Treatment objectives

Treatment objectives were primarily den-toalveolar, improving dental positions, midlinecorrection, overbite correction and a very accurateinterarch coordination. This last procedure is a keyfactor to achieve a good functional occlusion, na-mely proper incisal guidance, desoclusion by ca-nines in lateral movements and a final reciprocalprotected occlusion.



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Treatment progress

Maxillary and mandibular .022” pre-ajusted Edgewise mechanism / Roth prescripti-on was placed. Initial alignment and levelingwere achieved with a sequence of thermoacti-vated niti wires. Vertical control and deep-bitecorrection was achieved by using one set ofreverse Curve of Spee arches. After a sequenceof round stainless steel arches, proper arch formand coordination was reached through rectan-gular .019” x .025” SS arches, with individualtorque control plus finishing detailing.

Appliances were removed after 22 mon-ths of active treatment. The patient was instruc-ted to wear upper and lower Hawley retainers

full time in the first year, changing to partial timeuse after that.

Treatment results

The observed dentoalveolar alterations areseen in postreatment figures. Little skeletal modifi-cations occurred, as expected. Good teeth positi-ons were achieved, with proper overjet and over-bite, midline correction and nice upper and lowerarch forms. Important to note the solid intercuspalrelationship obtained as well as adequate incisalguidance. The key factor in eliminating posteriorinterferences was the strong canine contact in theworking side, sufficient enough to provide goodguidance and protection in lateral movements.

Fig. 3 – Finishing procedures

Fig. 4 – Post treatment photographs



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Conclusions

Good functional occlusion was achievedin a moderate crowed Class I malocclusion, withgood patient cooperation. Timely and contempo-rary orthodontic procedures based on solid gnato-logical principles changed a poor functional oc-clusal environment into a nice, pleasant and func-tional interarch relationship, probably preventingmany potential problems in the years to come.

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Fig. 5 - post treatment lateral movements



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Recebido em 20/8/2005; Aceito em 19/9/2005

Received in 8/20/2005; Accepted in 9/19/2005.



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