Making Occlusion Work: 2. Practical Considerations A.J. MCCULLOCK

Transcription

1 R E S T O R A T I V E RESTORATIVE D E N T I S T R Y DENTISTRY Mking Occlusion Work: 2. Prcticl Considertions A.J. MCCULLOCK Astrct: In the first of these two rticles, occlusl terminology, techniques for exmining the occlusion, rticultors nd interocclusl records were discussed. Here the uthors consider some of the prcticl pplictions. Dent Updte 2003; 30: Clinicl Relevnce: A prcticl knowledge of occlusion is required for successful plcement of the smllest nd lrgest restortions. stle mxillomndiulr reltionship should e developed to llow reproduciility of the jw registrtion nd stility of restortions nd teeth. The retruded position is the only reltively reproducile position of the mndile tht is physiologiclly cceptle. When the reorgnized pproch is indicted, nd this is in smll numer of ptients, the new ICP is estlished y: R estortions must e plnned nd designed to fit hrmoniously with the complexities of the neuromusculr control system, the temporomndiulr joints (TMJs) nd supporting structures of the teeth without introducing occlusl interferences. A stle posterior occlusion with smooth uninterrupted protrusive nd lterl movement of the mndile is necessry. Once the occlusion hs een ssessed, which my require rticulted study csts, the decision must e mde s to which type of occlusl scheme should e used for the restortions. TO CONFORM OR REORGANIZE? Before emrking on tretment the prctitioner must decide whether to provide restortions within the existing occlusl scheme (the conformtive pproch) or to chnge it deliertely (the reorgnized pproch). If the entire A.J. McCullock, BDS, MSc, FDS RCS, MRD, MRD RCS (Edin.), Consultnt in Restortive Dentistry, Lister Hospitl, Stevenge, Hertfordshire. occlusl scheme is to e reorgnized to crete new nd stle position, the finl restortions re mde to the new ICP tht coincides with RCP nd my involve chnge to the occlusl verticl dimension (see previous rticle for revitions). The fctors to e considered re given in Tle 1. A functionl stle posterior occlusion exists when enough teeth re in simultneous even contct to direct occlusl forces xilly, stilizing the positions of oth the teeth nd the TMJs. Approprite posterior stility distriutes occlusl forces over wide re, preventing dmge to the individul components of the mstictory system. Loss of posterior stility my result in: l incresed toothwer; l mechnicl filure of teeth or restortions; l hypermoility, drifting, rottion nd tilting; l mndiulr dysfunction. In the presence of mndiulr dysfunction, which is not lwys the cse in unstle ICP reltionships, l occlusl splint therpy to chieve muscle relxtion, 1 llowing the condyles to move into the retruded position; l elimintion of RCP ICP discrepncy using provisionl restortions, occlusl equilirtion, dditions to existing prtil dentures to restore the OVD, nd orthodontics; l finl restortions when mxillomndiulr reltionships re stle. In the previous rticle two theories were mentioned descriing idelized occlusions gnthology nd Pnkey-Mnn-Schulyer. A third concept, of dynmic individul occlusion, hs developed, sed on the fct tht not ll dentitions fit into prescried concept nd so more functionl pproch should e dopted. However, one fct is cler: tht n occlusion should e stle nd thus idelly ICP nd RCP should coincide when n occlusion is reorgnized. STABLE TOOTH CONTACTS The morphology of the occlusl surfces of restored posterior teeth is influenced y nterior guidnce nd Dentl Updte My

2 Posterior occlusion Stle Unstle No. of teeth for restortion Smll (>6) Lrge Slide from RCP to ICP Lrge/smll Lrge/smll Drifting of nterior teeth No Yes Mndiulr dysfunction No Possily the ngultion of the condylr pths. Stle occlusl contcts in ICP re generted using tripodized, cusp to foss or cusp to mrginl ridge contct reltionship ccording to preference, restoring the intercuspl reltion of the posterior teeth in the retruded position (Figure 1). In mny nturl dentitions supporting cusps contct opposing mrginl ridges in ICP, directing occlusl forces long the long xis of the tooth. The cusp to foss theory suggests tht restored cusps should contct tringulr fosse developed on the mesil or distl spects of posterior teeth. This pttern is suited to producing restortions ginst n existing occlusion. A tripodized occlusion hs ech of the supporting cusps contcting the opposing teeth t three points, suspending the cusp tips ove the opposing foss nd preventing them mking contct. Protrusive guidnce should immeditely seprte posterior teeth nd in lterl movement the working guidnce should immeditely disclude teeth on the non-working side. The steepness of nterior guidnce directly influences the ngle of the cuspl inclines. To chieve immedite posterior disclusion in cnine guidnce, mndiulr cusps must e le to glide etween mxillry cusps without interference. When nterior guidnce is steep cusps cn e mde steep nd the fosse deeper. = Stle ICP = Unstle ICP Conformtive pproch Reorgnized pproch Tle 1. Fctors to e considered when considering provision of restortions. the occlusion hs een ssessed nd unwnted contcts identified, djustments cn e mde in the mouth, if uncomplicted, or through tril djustments on rticulted csts (Figure 2) to estlish their effect. Such mock equilirtions llow n ccurte ssessment of the effects of tooth djustment nd correct plnning of the stges of the djustment without dmging the teeth. Selective occlusl djustment is B indicted efore restortion when: l the opposing tooth hs overerupted into n existing undercontoured or scooped out restortion, producing plunger cusp; l tilted or over-erupted teeth hve produced n uneven occlusl plne; l the tooth to e restored hs non-working side interference; l the tooth to e restored cretes n occlusl interference in the retruded pth of closure. Contcts in RCP should e djusted first, then the lterl nd, finlly, the protrusive interferences. Before the teeth re touched with ur the effect of ech djustment must e nticipted. Adjustments to contcts on mxillry teeth will move the point Figure 1. () Cusp tip to foss contct. () Tripodized reltionship: ech cusp tip contcts the opposing tooth t three points. L OCCLUSAL ADJUSTMENT Occlusl interferences occurring during mndiulr movement my require djustment efore restortive procedures re contemplted. Once Figure 2. () Articulted csts covered in indictor vrnish. () Tril djustments to show the effect of the procedure on the next point of contct. 212 Dentl Updte My 2003

3 ojectives for vrious clinicl situtions of incresing complexity is discussed in the following prgrphs. Figure 3. () Checking tooth contcts with Shimstock efore cementing ridge. () Sme contcts verified fter cementtion. of contct ucclly nd mesilly; those on mndiulr teeth will e moved lingully nd distlly. This will help in deciding which points to djust when opposing teeth hve een mrked y rticulting pper, rememering tht cusp tips re scrosnct. If, for exmple, the mrked contct flls on the lingul fcing incline of mxillry uccl cusp nd the uccl fcing incline of the opposing mndiulr cusp, the ltter contct should e djusted s the contct will then move towrds the centre of the tooth. For more detiled informtion reders re referred to expnded texts on the mechnisms of occlusl djustment. 2 y ensuring: tooth-to-tooth contct in ICP; no slide from RCP to ICP if reorgnizing the occlusion; no occlusl interferences; correct guidnce in lterl excursions. l There should e no mndiulr dysfunction. l Thickness of restortive mterils must e dequte. l Occlusl contour of restortions must e correct. l Occlusl verticl dimension must e correct. The prcticl ppliction of these Smll Numer of Units to e Restored A single unit or couple of units must fit into the existing occlusl scheme (conformtive pproch) nd provide the correct supporting cusp contcts. Before tooth preprtion the occlusl contcts must e checked with rticulting pper nd Shimstock, not only on the tooth to e prepred ut lso on the djcent teeth. The sme contcts cn e verified on the rticulted working csts. At the try-in stge, ICP nd lterl contcts should e checked with rticulting pper on the restortion nd Shimstock on the djcent teeth (Figure 3). When the distl tooth in n rch is prepred it is especilly necessry to ensure the occlusl record is ccurte, s errors cn redily e introduced with the verticl dimension if the csts re tipped or rotted. One wy to gurntee ccurcy is to try-in selfcuring crylic resin copings, ensuring RESTORATION OF POSTERIOR TEETH The posterior teeth provide stle verticl nd horizontl reltionships etween the mndile nd mxill. When plnning ny posterior restortion, the prctitioner must consider the following questions: l Is ICP stle? l Wht re the nterior tooth contcts? l Wht design of tooth preprtion? l How even is the occlusl plne? l Occlusl verticl dimension dequte or reduced? l Wht type of occlusl scheme is desirle conformtive or reorgnized? The ojectives re: l To leve stle occlusl contcts Figure 4. () Self-curing crylic copings on distl utments to verify occlusl contcts on the cst. () Ensuring contct nd ssessing ville spce for correct thickness of mteril for crown. Figure 5. () Single-qudrnt interocclusl record nd () self-curing crylic copings. The overerupted first molr hs een prepred nd wxed-up to produce n even occlusl plne. 214 Dentl Updte My 2003

4 c e the occlusl contcts on the teeth re the sme s on the csts (Figure 4). The thickness of the copings cn lso e mesured to see how much ville spce hs een creted. Single Qudrnt Following loss of posterior teeth in qudrnt the ntgonistic teeth my over-erupt or tilt, producing n uneven occlusl plne. Unless the overerupted teeth re recontoured y selective occlusl djustment or restortion, ny replcement of the missing teeth will hve contct in ICP nd n irregulr occlusl form tht is determined y the shpe of the opposing teeth. By eliminting the irregulrities, hrmonious occlusl contour will e creted tht ensures stle ICP contcts nd voids lterl interferences. The replcement hs een developed to modified occlusion, ut s ICP remins d Figure 6. () Occlusion in ICP t reduced verticl dimension. () Teeth in RCP showing restored verticl dimension nd cretion of spce nteriorly. (c) Dignostic wx-up in RCP. (d) Composite resin uild-ups on nterior teeth in RCP t the new verticl dimension. (e) Metl cermic crowns duplicting the occlusl scheme developed using the composite restortions. unchnged the pproch is conformtive. The inter-occlusl record (Figure 5) is tken following djustment nd tooth preprtion. This only needs record of the reltionship on the prepred side, providing full rch impression hs een tken nd there re dequte occlusl contcts on the contrlterl side to mintin stility. Opposing Qudrnts In this sitution the occlusl plne nd curves of Spee nd Monson cn e restored to produce the most fvourle occlusl contcts. The OVD is mintined y tooth contct nteriorly nd on the contrlterl side, posteriorly y the condylr position in ICP using the conformtive pproch. When the utment teeth form interferences nd ICP is unstle it is dvisle to reorgnize the entire occlusion. Reduced Verticl Dimension Associted with Short Clinicl Crown Height Both the OVD nd ICP my e ltered in this sitution (Figure 6). Such cses usully require restortion in RCP nd the production of stle nd coincident ICP using the reorgnized pproch. Occsionlly, the nterior tooth contct nd condylr position re stle, llowing the existing ICP to e used. The detils of recording the OVD were discussed in the previous rticle. On rticulted study csts mounted in RCP t the correct OVD, occlusl djustments re crried out to eliminte ny discrepncy etween RCP nd ICP. These re then crried out on the ptient s teeth s n occlusl equilirtion. On the csts, the teeth to e restored re next prepred nd wxed up to full contour, ringing them into occlusl contct with the opposing rch. The new ICP nd OVD re mintined y developing the cusp height nd foss depth. Temporry restortions re constructed from this wx-up nd cemented onto the prepred teeth; minor occlusl djustments my e necessry to develop coincident ICP nd RCP. The ptient is reviewed over severl weeks to check his/her dpttion to the new occlusl scheme. This is determined y lck of symptoms from the TMJs, feeling of comfort nd stility of the restortions. Definitive restortions re then mde duplicting the newly estlished occlusion. Multiple Units in One Arch If most occlusl contcts will e lost in the preprtion of teeth, then reorgnized pproch should e used. A dignostic wx-up on rticulted csts in RCP will determine the new position of ICP nd temporry restortions will e constructed mintining the occlusl verticl dimension (Figure 7). Full Mouth Rehilittion The restortion of ll four qudrnts together requires tht ll the Dentl Updte My

5 with rticulting pper. Mtt gold surfces more esily show such mrks nd should e used t the try-in stge to verify occlusl contcts efore polishing nd cementtion. Gold occlusls would e preferred where: c d l there is history of prfunctionl ctivity; l clinicl crown height is reduced; l optiml occlusl control is necessry in the reorgnized pproch. Figure 7. The replcement of mxillry denture nd crowns. () The displced mxillry denture. () Pltl view of the restortions nd edentulous spce. (c) Complete rch dignostic wx-up in RCP. (d) Temporry ridge replcing ll the mxillry restortions. The missing teeth were replced y single tooth implnts nd the remining teeth crowned. determinnts of occlusion e developed in unison. It is dvisle to provide long-term temporry restortions in such cses s the ptient s tolernce to chnges in ICP, RCP, excursive movements nd possily the OVD must e monitored over long time. The proposed chnges cn e grdully introduced on the temporry restortions, which re esier to djust or dd to. Such restortions should hve metl sustructure overlid with crylic or composite resin. The principles of reconstruction re no different from those lredy descried. The tretment pln is divided into four stges: 1. Occlusl splint therpy. 2. Occlusl equilirtion so tht ICP = RCP. 3. Restortion of the nterior teeth. 4. Restortion of the posterior teeth, either y opposing qudrnts or ll t one time. stle ICP contcts. The wer chrcteristics of direct composite resins re less fvourle nd more rsive to the opposing dentition: this mteril should not e used when restoring lrge cvities where tooth contct is solely on the mteril. Smll Clss II restortions cn e restored with composite, providing tht the occlusl contcts re primrily on the tooth nd not the mteril. Porcelin versus Gold Porcelin occlusl surfces offer improved posterior esthetics ut the technique for developing them is more difficult thn in gold nd the highly polished surfce does not redily mrk RESTORATION OF ANTERIOR TEETH Preopertive considertions: l stility of ICP; l reproduction of correct pltl contours; l tooth preprtion; l metl coping design; l protrusive nd working guidnce; l incisor reltionship; l phonetics nd ppernce. Ojectives (in ddition to the posterior ojectives): l even distriution of forces in incisl guidnce; l immedite posterior disclusion (except in Clss III occlusions). Anterior Guidnce The nterior teeth re in lnced position determined y the lips, tongue, occlusl reltionship nd Mterils for Restoring Occlusl Surfces Amlgm is n excellent mteril for restoring posterior teeth s it hs high resistnce to wer, producing Figure 8. () A Clss II division II incisor reltionship with complete overite. () Shortening the lower incisors nd uilding out the pltl surfces cretes stle occlusl contcts. 216 Dentl Updte My 2003

6 c e lveolr one support. Chnges to the shpe of the teeth cn produce unwnted movement if these fctors re disrupted, leding to migrtion, rottion over-eruption or formtion of distem. Restortions must e plced in this lnced envelope to chieve stility nd longevity. Anterior guidnce should provide smooth even contct on s mny nterior teeth s possile from ICP through the excursions discluding the posterior teeth immeditely. It should e shllow, work hrmoniously with condylr guidnce nd fit in with the skeletl nd incisor reltionship, ppernce nd speech. If single tooth is to e restored the existing guidnce cn e redily duplicted. When ll the nterior teeth re to e restored some chnges to the guidnce, crown position nd ppernce cn e mde. d Figure 9. () Filing ridgework. () Short clinicl tpering crown preprtions. (c) Immedite temporry ridge. Anterior guidnce ws estlished on the ridge in the mouth, llowing the retention of the reprepred teeth to e checked s well s the stility of the occlusl contcts. (d) A customized incisl guidnce ws produced on the rticultor to copy the nterior guidnce developed in the mouth. (e) The definitive crowns nd ridge restoring the upper rch using customized incisl guidnce tle, ensuring dupliction of the pltl surfces of the temporry restortions. In Clss II division I incisor reltionships the overite nd overjet will e incresed, leding to the mndiulr incisors occluding to the pltl spect of the cingulum close to the dentogingivl junction. If this reltionship is copied in mxillry restortions, ICP contcts my ecome unstle, leding to n increse in tooth moility, migrtion nd splying. The incisl guidnce cn e ltered y uilding out the pltl surfces of the restortions to provide occlusl rests in the re of contct of the lower teeth; it my lso e necessry to shorten the mndiulr incisors. The edges re reduced horizontlly to produce flt rther thn evelled incisl edge, which would mke it difficult to chieve stle contcts (Figure 8), especilly in Clss II division II reltionships. This will crete hrmonious movements from ICP into protrusion nd lterl excursions. Anterior guidnce cn e duplicted on n rticultor with customized incisl guidnce tle. Self-cure crylic resin is shped y moving the upper memer of the rticultor while mintining contct with the incisors nd cnine tooth on the study csts. The incisl pin crves out pth in the setting resin resemling Gothic rch trcing (Figure 9). This technique is used when new reorgnized guidnce to which ptient hs dpted hs een estlished on multiple temporry crowns or when the existing guidnce must e copied. The cnine tooth hs fvourle crown/root rtio for soring occlusl forces s well s root configurtion providing greter surfce re, more periodontl ligment nd proprioception thn djcent teeth. 3 It is eminently suited to guide lterl excursive mndiulr movements nd produce immedite disclusion of the posterior teeth. Scife nd Holt 4 reported n incidence of 57% ilterl cnine guidnce in 1200 individuls. There is little scientific evidence to ssist in identifying exctly wht cnine guidnce should e. McHorris 5 suggested tht the disclusive ngle (which governs the pltl contour of the working cnine) should e 5 o greter thn the condylr guidnce ngle. There re severl mechnicl dvntges in providing cnine guidnce: l esier ccess in the front of the mouth for djustments; l smooth mndiulr movements cn e produced with immedite disclusion posteriorly; l recording nd producing cnine guidnce is less complicted, oth cliniclly nd techniclly. Occlusion on Pontics Occlusl contcts on full-sized pontics should e in ICP. When the cnine is replced y pontic on fixed ridge cnine, guidnce cn e developed, providing there re nterior nd posterior retiners. If cntilever ridge 218 Dentl Updte My 2003

7 is mde using the premolrs, group function should e developed. The occlusl contcts on simple cntilever ridge must e in ICP on oth units ut the pontic must e free of ny lterl contcts. This reduces the lterl forces on the pontic tht would otherwise cuse lever effect, forcing the ridge to rotte outwrds. CONCLUSION The sic principles in restoring nterior nd posterior teeth hve een discussed, highlighting the necessity for creful preopertive plnning. The conformtive pproch is pplicle to most ptients: reorgnizing n occlusion requires high level of skill nd knowledge from oth technicin nd clinicin to ensure good result. A functionl dynmic pproch to occlusion sed on theoreticl principles is useful concept in restortive dentistry. Most ptients require little more thn n cceptnce of their existing occlusions, ensuring tht restortions fit into their individul schemes, providing they re hrmonious nd stle. There re numer of pproches to extensively reorgnizing the occlusion tht will produce n cceptle result, providing the underlying principles of ech theory re fully understood nd their individul prcticl ppliction dhered to. ACKNOWLEDGEMENT The uthor thnks Mr Stephen Dvies for his constructive comments on these two rticles. REFERENCES 1. Gry SJ, Dvies SJ, Quyle AA. A Clinicl Guide to Temporomndiulr Disorders. London: BDJ Books, 1997; pp Dwson PE. Occlusl djustment In: Evlution, Dignosis nd Tretment of Occlusl Prolems. St Louis: C.V. Mosy, 1974; pp Bonguro JG, Dusz GR, Bowmn DC. Aility of humn sujects to discriminte forces pplied to certin teeth. J Dent Res 1969; 48: Scife PR, Holt JE. Nturl occurrence of cnine guidnce. J Prosth Dent 1969; 22: McHorris WH. Occlusion with prticulr emphsis on the functionl nd prfunctionl role of nterior teeth. J Clin Orthod 1979; 13: 684. BOOK REVIEW Invisile Orthodontics: Current Concepts nd Solutions in Lingul Orthodontics. By Giuseppe Scuzzo nd Kyoto Tkemoto. Quintessence Books, New Mlden, 2002 (173 pp., h/). ISBN Lingul orthodontics hs een prt of the orthodontic profession for some time, lthough pprently only out 10,000 orthodontic cses re treted using this technique in Europe, Jpn nd the USA. Considering the high numers of orthodontic cses treted ech yer worldwide, the numer of clinicins using lingul orthodontics must e very smll. The uthors hve written this ook lrgely on their own experiences nd re well supported with excellent illustrtions of cse studies. The ook strts y introducing the topic of lingul orthodontics imed t specilist orthodontists. It skips over the dignostic nd therpeutic considertions in lingul orthodontics nd suggests useful hints for successful tretment. These include the use of loop mechnics, power rm uxiliries nd force delivery systems nd mechnics in lingul orthodontic extrction cses. Two chpters of the ook re devoted to four different lortory techniques in the pre-clinicl set-up of lingul orthodontics. The ook seems to emphsize the relince upon good technicins nd lortory fcilities which my e reson for its limited use. The well illustrted cse reports indicte how the lingul pplince technique cn e utilized to high stndrd. The mlocclusions presented certinly require some lterl thinking nd oldness in execution, even for most wellsesoned orthodontists. Two contrsting iomechnics, closing loops nd sliding mechnics, re illustrted t different stges of tretment. Advntges nd pitflls of the tretment mechnics re mentioned s the cses progress to completion. The precision involved in loop mechnics not only ers hevy resemlnce to lorious wire ending in edgewise mechnics, ut seems more demnding when trying to fit these systems intr-orlly. Sliding mechnics lso requires greter cre ecuse the force moment rtios re pplied differently from the lingul spect nd these then tend to tip teeth in unwnted directions. In the finl chpter, the uthors descrie the vrious wys in which the finished results re retined with lingul retiners, cler positioning splints nd trnsprent retiners. This ook will e of interest to postgrdute students nd orthodontic prctitioners who wnt to develop privte invisile orthodontics prctice. It provides n excellent overview of the lingul technique nd hs rought to light the immense technicl skills from oth lortory nd clinicin in the tretment of single cse. Although this ook is not fully comprehensive, it does provide structured pproch to lingul orthodontics. C.H. Ku nd S. Richmond Crdiff Dentl School Dentl Updte My