Usefulness of occlusal splints

DOI: 10.1051/odfen/2012104 J Dentofacial Anom Orthod 2012;15:204� RODF / EDP Sciences

1

Conflicts of interest declared by author: NONEArticle received: 09-2011.

Accepted for publication: 11-2011.

Usefulness of occlusalsplints

Jean-Francois CARLIER

ABSTRACT

Dentists often use occlusal splints in the management of occlusodonticproblems. Because they are considered to provide non-invasive and reversibletreatment they are therapeutic devices that conform well to the currentphilosophy governing protocols for therapy of the masticatory system. Properdesign and placement of occlusal splints requires that they respond to preciseindications and that practitioners fabricate and maintain them with scrupulouscare to assure that patients benefit from them. Splints help practitionersadjust the relationship between the jaws either by suppressing blockage ofteeth to relax muscles or by repositioning the condyles in the articular fossasto recapture discs or to reduce painful excess intra-articular pressure derivedfrom degenerative diseases.

Occlusal splints are also suitable as diagnostic tools to validate and evaluatecontributions of behavioral, postural, and psychosocial factors to the multi-factorial etiology of malfunctions of the masticatory apparatus. The simpleintroduction into a patient’s mouth of an appliance whose benefits have beenwell described to that patient will serve as a forward step in the psychologicalmanagement of a TMD problem, especially if bruxism is one of its components.

KEY WORDS

Occlusal splint,

Inter-maxillary relationship,

Articular repositioning,

Bruxism.

Address for correspondence:

J.-F. CARLIER,3, rue LeonTassin,02880 [email protected]

Article available at http://www.jdao-journal.org or http://dx.doi.org/10.1051/odfen/2012104

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Published reviews of the literaturefrequently remind readers that accord-ing to the principles of evidence basedmedicine there is no justification fortreating malfunctions of the mastica-tory system, temporo-mandibulardysfunction (TMD) with occlusal equi-libration or rehabilitation. The absenceof EBM documentation demonstratingthe effectiveness of specific, and de-monstrably reversible, treatment mod-alities like ortheses is not, however,proof that they are obsolete. Greenand Laskin7 have shown the impor-tance of understanding the patient’spsychosocial environment and familyrelationships in TMD therapy. The pla-cebo effect, they add, plays a role,pointing out that an orthesis acts, inpart, by manifesting the treatment rolethe practitioner has undertaken.Other, more recent, studies4 have vali-dated the relaxing effect of the block-ing action of an orthesis.

Even if an occlusal splint is not ne-cessarily indicated as the first step in

TMD therapy, it does constitute a re-versible, easy to implement treatmentthat can validate a diagnostic hypoth-esis as well as an etiology-based ther-apeutic device for correction of atemporo-mandibular malady12. Beforeusing it, practitioners must complete acomplete a clinical examination thatsuggests a relationship betweenpathological occlusal relationships andthe appearance of TMD or of muscu-lar or articular pain.

The reversible nature of this appli-ance resides in its innocuous effecton the dental structures that it coversbut does not modify and, above all,by the practitioner’s scrupulous con-trol of its conception, its fabrication,and the way the patient wears it. Asplint can no longer be deemed re-versible if it is based on anteriorteeth or upon right or left posteriorteeth only and is worn for severalmonths because then it will causenoticeable physiological changes ofintrusion or extrusion of teeth.

1 – THE MUSCLE RECONDITIONING SPLINT

A muscle-reconditioning splint be-comes indicated as soon as practi-tioners determine that the pain andmalfunctions affecting patients aremuscular in origin. They should bedesigned to suppress occlusalanomalies and to neutralize the al-terations of form and position ofteeth that cause micro-displacementsof the mandible in the approach tomaximal intercuspation. These displa-cements in the position of occlusalequilibrium are caused by asynchro-nic contractions of the bundles of

elevator and other muscles asso-ciated with achievement of centricocclusion.

For this reason the splint is madewith a flat and smooth surface toavoid creating any obstacle to a pa-tient’s finding centric position for themandible during closure followingcontraction of the muscles of mastica-tion. It is imperative that the splint beconstructed of a material hard enoughto make the forces exerted on period-ontal mechano-receptors as ubiqui-tous as possible. The simultaneous

JEAN-FRANCOIS CARLIER

2 Carlier J.-F. Usefulness of occlusal splints

nature of the contact of the splint’sbase with opposing teeth and theequality of the occlusal forcesthus perceived by the mechano-receptors instead of what they feltfrom varied transmission throughupper tooth to lower tooth contactsreduce and soothe the activity of themuscles of mastication.

The use of a soft and deformablesplint provokes an excess of proprio-ceptive information from musclesand periodontal tissues that intensifycrackling sounds related to munchinghabits. By multiplying incoherent pro-prioceptive information soft splintstend to reduce muscular rest periods.

An orthesis employed in TMDtreatment should create a situation ofanatomic and physiological equili-brium by re-establishing synchroniza-tion of muscular contractions, makingaxial forces symmetrical and welloriented while altering the physiologi-cal status of the patient as little aspossible.

The appliance should be a 1.25 mmthermoformed, semi-rigid bite platecovering the occlusal surfaces and ex-tended to the buccal collars of theteeth to insure maximal retention. Itslingual extension should go no furtherthan 5 mm above the lingual collarsof the teeth. These limitations, whichimprove the splint’s esthetics anddecrease bulkiness, are designed toincrease patient cooperation.

The splint has a flat posterior sur-face and, if necessary, incorporates acanine-to-canine anterior reinforce-ment to guide the mandible into acentric position as it closes and todis-occlude the posterior teeth in ex-cursive movements (fig. 1). Contactswith the teeth of the opposing jaw

should be as widespread as possibleand only the contact points of thesupporting cusps should be pre-served to minimize the stimulation ofperiodontal membranes that pro-vokes muscular hyperactivity.

In choosing which jaw should sup-port the splint, the advantages incomfort of placement on the mand-ible are this site’s lower visibility andits lesser interference with phona-tion11 and the greater access it givesto practitioners in adjusting contactpoints with direct vision. Practitionerswill make their final choice betweenplacement of an orthesis on the max-illa or the mandible by the amount oftooth substance they will have to re-move in occlusal equilibration and bythe extent of maxillary protrusion soas to limit the invasive nature of theappliance (fig. 2).

The neuromuscular reconditioningsplint should be made in the labora-tory on models mounted in centricrelation and with a slight increase invertical dimension on a simple articu-lator.

Figure 1Only the supporting maxillary cusps (blue markings)contact the plastic surface of the splint. The canineguides (in red) assure centric relation.

USEFULNESS OF OCCLUSAL SPLINTS

J Dentofacial Anom Orthod 2012;15:204 3

The thickness of the splint drawnout in the thermo-formation will, onthe average, be .7 mm, just enough toallow for its final surface to beflattened out. The practitioner ortechnician can fill in the occlusal irre-gularities left by the thermo-formingprocess with photo-polymerizableplastic to optimize occlusal stability(fig. 3).

When placing the splint in themouth, it is essential for the practi-tioner to verify its adaptation, its sta-bility, and all tests of comfort forpatients that the thermo-forming pro-cess suits admirably. The under-surface of a thermoformed devicefits far better than plastic plates

made on a plaster models that are in-variably deformed by bubbles orother irregularities, But if a thermo-formed splint displays any initialinstability, the operator can easily cor-rect this defect by heating its basewith a flame and re-seating it in themouth and having the patient bitedown. In this way a defect in thebase of a thermo-formed splint whenit is first inserted actually helps thepractitioner to obtain better retentionwithout giving rise the wedge effectthat would result from a similar man-euver with an acrylic plate.

The operator regulates occlusion ofthe splint by using 40 l articulatingpaper to help in spot grinding to gen-eralize cusp contacts when patients,guided by the practitioner’s hand,close gently along a physiologicallydetermined arc. If operators try tomake these adjustments after pa-tients have closed freely on articulat-ing paper, with no guidance from thedentist, under the voluntary actionof the elevator muscles, they willrisk reproducing the deviated spatial

Figure 3A technician is filling depressions in splint with photo-polymerizable plastic to make a smooth surface.

Figures 2a to 2dThe extent of maxillary protrusion is a major determi-nant in decision to place splint on maxilla or onmandible.



situation of the mandible caused byasynchronic contractions.

TMD splints should be worn pri-marily at night, but in severe cases itis advisable for patients to wearthem in the daytime as well. As mus-

cular strains begin to disappear, prac-titioners should make regularadjustments of splints, which, in anycase, should not be worn for morethan three months.

2 – THE ANTERIOR STOPOn the principle of the Lucia Jig,

which was initially designed to regis-ter centric relation, an anterior stop ismade to constitute a smooth obstacleon the path of a patient’s physiologi-cal closing1, which in disengaging theposterior teeth deprograms afferentproprioceptive messages to periodon-tal receptors that originate asynchro-nic muscular contractions. Whenincisor teeth contact this flat surface,the oral neuro-muscular complex isencouraged to relax, a necessary con-dition for clinical registration.

One of the principle attractions ofthis anterior stop is the ease withdentists can construct it in the mouthduring an emergency appointmentand instantly control pain from crispa-tions of the lateral ptyergoids, and, atthe same time confirm the muscularorigin of the TMD.

To construct the stop, the practi-tioner forms a ball of photo-polymer-izable plastic (Revotek LC�, GC) orthermoplastic paste (ISO Functional�,GC), places it over the maxillary cen-tral incisors, already treated with aseparating solution, and covers theirincisal edges and their palatal sur-faces up to the edge of the hard pa-late in a layer thick enough tokeeping the posterior teeth apartabout 1 mm. The practitioner re-moves the stop from the mouth afterit has hardened and grinds it suffi-

ciently to reduce contact with man-dibular incisors to a single pointwhen patients close on it.

A dentist can make an instantanterior stop simply by cutting a burbox to the width of the two centralincisors, filling it with thermoplastic,and holding it in over the incisors un-til the material sets (fig. 4), thus ac-quiring the required smooth flatsurface with no adjustments neededfor its creating the proper amount ofposterior disengagement.

The anterior stop, or bite block, is in-dicated for short-term treatment andfor cases with acute symptoms invol-ving both muscles and the TMJ, butdentists must be follow it up with aposterior splint or with occlusal equili-bration.

Contra-indications for continuing towear an anterior stop are strict:

– in cases of disc displacement it willaggravate the disorder by increas-ing articular compression in theretro-disc area, especially for pa-tients who have not yet receivedoral behavior counseling on how toreduce muscle crispation;

– for patients whose wearing of theanterior stop has provoked ingres-sion or extrusion of teeth. Theyshould not wear an anterior stop formore than a few days;



– when the device is small and notwell retained, patients should notrisk swallowing it by wearing it atnight.

The transitory character of themuscle relaxation obtained2, the notnegligible risk of aggravating the in-stability of the condylo-disc complex,

and the iatrogenic forces exerted byan anterior splint on the teeth it cov-ers all limit the length of time it canbe worn before the dentist registersinter-maxillary relationships and trans-fers models to an articulator forconstruction of a posterior muscle re-conditioning splint.

3 – THE ARTICULAR REPOSITIONING SPLINT

Disorders of the masticatorysystems are often related to inter-nal derangement of the temporo-mandibular articulation and the painassociated with it are an indication ofthe muscular hyper-activity patientshave adopted in an unconscious ef-fort to maintain the components ofthe TMJ in place. An orthesis canhelp to reposition structures that havebeen displaced by constraints pro-voked by trauma or a loss of posteriorinter-cuspation. Repositioning splints,also called disc recapturing or anteriorrepositioning splints, place the mand-ible in a position that the dentist hasdetermined will re-establish the stabi-

lity of the condylo-disc complex, re-duce overloading of TMJ structures,and eliminate immobilizing muscularcontractions. The dentist makes in-dentations on the splint surface thatwill guide the mandible into a new in-ter-cuspation8 that will encourage atherapeutic TMJ relationship (fig. 5).

This splint, made on a base thermo-formed over a model of the mandible,will have deep indentations or even arepositioning wall that will oblige themandible to close into a therapeuticposition encouraging disc recapture.

Repositioning splints are indicatedin cases of spontaneous reducible

Figure 4The smooth surface of an anterior stop made with a cut-down bur box makes it available forimmediate use with no adjustments.



disc luxation and are most successfulwhen the clicking sounds of openingand closing occur close to the pointof maximal intercuspation.

Dentists can note the limiting zoneof disc recapture when clicking isheard on closure, which is why manyauthors3,5,6 recommend discerningthe correct therapeutic position forthe mandible when it is movingdistally.

To accomplish this, dentists askpatients to open their mouths untilclicking is heard, then to place the in-cisors in edge-to-edge position. Theythen slide their teeth back into maxi-mum occlusion as the mandible isguided by the incisal contact and thediscs are held in place by pressure ofthe heads of the condyles againstthe anterior slope of the glenoidfossa. The practitioner then deter-mines, at what precise dental posi-tion the clicking of return occursindicating the disc displacement ac-companied by a projection click of

the mandible. After helping the pa-tient make several retraction move-ments, the dentist registers thecorrect therapeutic position by takinga three layer posterior hard wax biteMoyco Beauty Pink X (fig. 6) as theanterior teeth are disengaged for theduration of the posterior contact.The interposition of the wax duringthe mandibular retrusion constitutesa resistance that helps the patient tomaintain condylar placement.

The dentist can also determine thepoint of return clicking by axiographicregistrations that indicate on para-con-dylar recording plates the coordinatesof the forward jump that accompaniesthe luxation. The operator determinesthe correct therapeutic position on thearticulator, ahead of the point of returnclicking by blocks placed in the con-dyle box or by regulating the propul-sion screw of the condylar box (fig. 7).The insertion of a 1 mm thick wedgemade by folding the lead paper coverof an intra-oral X-ray film to obtain thenecessary decompression for recap-ture of the disc.

Figure 5Blue marks show the deep indentations defining therepositioning of the mandible.

Figure 6The therapeutic position of disc recapture is registeredas the mandible moves distally.



The operator fabricates the man-dibular splint on models mounted onan articulator in the therapeutic posi-tion provided by the wax bite. It cov-ers the occlusal surfaces of theposterior teeth and its transparentplastic fills the inter-arch space cre-ated by the lowering of condyles inthe disc recapturing forward positionachieved by the wax bite. The inden-tations in the posterior portion of thesplint are about 2 mm deep and con-stitute a guidance cone for each an-tagonistic cusp (fig. 8), encouragingthe mandible to enter the therapeuticposition as it approaches maximal in-tercuspation. The anterior teeth arenot covered so that contact in propul-sive movements will be maintainedand so that proprioception in gui-dance of mandibular movements willbe encouraged.

When the splint is placed in themouth, if the maxillary teeth immedi-ately seek out the indentations in itthis validates the accuracy of its ther-

apeutic position. Patients are usuallyasked to wear repositioning splints atall times except when eating.

In fact it is almost impossible tochew food while wearing splints be-cause the functional schema of mas-tication cannot be established untilthe TMJ and muscular problemshave been resolved. The indentationsare negative imprints of opposingteeth; they are not cusps that cangrind up food particles. At best, pa-tients chewing with a splint in placewill mutilate it and eventually destroyit; at worst they will generate un-controllable constraints on oral struc-tures worse than the occlusaldisturbance the splint was designedto neutralize.

TMD signs and symptoms begin todissipate as the splint progressivelyurges the mandible into a more for-ward position in accordance with therules of occlusal equilibration, thuspermitting the disc to be recaptured ina less anterior position in the glenoidfossa, while conserving the coopta-tion of the TMJ components9. These

Figure 7The propulsion screw maintains the head of thecondyle in a position in advance of the clicking.

Figure 8The indentations in the splint constitute a guidancecone for each cusp of the maxillary posterior teeth.



successive adjustments end up trans-forming the repositioning splint into asplint stabilizing the new therapeutic

articular position that accompanies anew occlusion that is mesial to the pa-tient’s habitual intercuspation.

4 – THE DECOMPRESSION SPLINT

Irreducible disc luxation is charac-terized by a loss of discal cooptationin maximal intercuspation and by lim-itation of mouth opening caused bythe disc’s being tilted forward and in-ward that provokes a painful stretch-ing of the bilaminary zone.

When an occlusal splint is intro-duced into the mouth the space be-tween the head of the condyles andthe surface of the glenoid increases inan amount equal to the splint’s thick-ness thus providing a decompressionof the inflamed TMJ structures.

Technicians can make a simplethermoformed decompression splinton a patient’s mandibular model with-out mounting it on an articulator. Theresultant uniform thickness of the de-vice will lower the heads of the con-dyles and advance the mandible

slightly after the few moments ittakes the patient to adjust to thenew biting surface. Dentists can in-crease the thickness of a splint uni-laterally in a selected area to relievethe pain of capsulitis and limit com-pression caused by edema in the bi-laminary zone (fig. 9). Patients areasked to wear the device at all timesfor a three-week period. As pain de-creases in intensity, dentists can be-gin treatment designed to eliminatethe etiological factors. If the patientcontinues suffer from pain afterwearing a decompression splint forseveral weeks, the dentists shouldadjust it by adding plastic to the oc-clusal surface.

In cases of arthritic degeneration,decompression splints can be used

Figure 9A TMD decompression splint made by adding plastic tothe region of teeth 46 and 47.

Figure 10The stabilization splint re-establishes guidance andblockage of the mandible.



to reduce bone-to-bone contact inthe TMJ to allow tissue repair andavoid development of ankylosis.These splints should be made oftransparent plastic on models moun-ted in centric occlusion on articula-

tors. The splint covers the fullmandibular arch and carries lightindentations to assure stable inter-maxillary relationships for severalmonths (fig. 10)

5 – THE STABILIZING SPLINT

Overall, no matter what its originalobjective may have been, any inter-occlusal splint is destined, after pro-gressive adjustments, to become asplint that stabilizes the mandible inthe desired reference position thathas been obtained.

In this role it establishes a newfunctional occlusal schema, withstructures of guiding, centering, andsolidifying cuspation, that can be vali-dated over a period of several months

until the dentist decides it is appropri-ate to undertake definitive stabilizationtreatment with additive or subtractiveocclusal equilibration, with pros-theses, or with ortho-dontics.

This stabilization can take the formof wearing full arch nighttime occlu-sal protective devices for patientswho have grinding, clenching, orbruxism habits that erode teeth orimperil prosthetic restorations.

6 – THE NOCTURNAL PROTECTION SPLINT

Bruxism is a nocturnal parafunctionthat, in its abrasion of teeth, di-minishes their capacity to guide andstabilize intercuspation and createswear facettes that exacerbate thecondition. We now know that occlu-sion itself does not cause bruxismand that splints cannot stop it. Butthey can serve as a protective shieldsbearing the brunt of erosion in placeof the teeth and must be repaired orreplaced when they become too thinor too fragile to play a preventive role.

Protective splints take the formstabilization splints made on eitherarch (fig. 11) of hard plastic coveringall the teeth. They are made on mod-els mounted in centric occlusion onan articulator where they are equili-

brated before being delivered to thepatient.

Figure 11Nocturnal bruxism protective splint.



7 – CONCLUSION

In this article no attempt has beenmade to present a complete assess-ment of all the ortheses proposed fortreatment of TMD because their num-ber is vast and their numerous authorssupport their proposals with powerfularguments. But at the end of the day,or night, with regard to bruxism, be-cause these appliances are removableit is the patient who determines theirefficacy either because of their unob-trusiveness physically or esthetically,because of the ease of wearing them,and, most important, by the extent ofthe patients’ cooperation with thedentist’s therapeutic efforts.

Even though occlusal ortheses arethe most popular TMD treatmentmodality and the easiest one to fabri-cate and to manage, dentists must

take into account two factors thatreaching the treatment objective re-quires: an accurate diagnosis and aneffective plan of treatment. And,above all, for effective therapy it isimperative that along with deliveringthe appliance dentists must providethe patient with a complete and com-prehensible explanation of what atemporo-mandibular disorder consistsof. And it is equally vital that patientsunderstand what the stakes of thistreatment are and what role they playin its execution.

The occlusal splint, in the final ana-lysis, is one element of a global ther-apy, an instrument, essentially, ofpatients taking personal charge oftheir own therapy10.

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6. Gelb H. Clinical management of head, neck and TMJ pain dysfunction. Philadelphia: WBSaunders, 1977.

7. Greene CS, Laskin DM. Splint therapy for the myofascial paindysfunction (MPD)syndrome: a comparative study. J Am Dent Ass 1972;84(3):624-8.

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Usefulness of occlusal splints