Redistribution of Leverage for Ant Teethpdf
Redistribution of Leverage for Ant Teethpdf
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  1. <:;cientitic <:;ectionRedistribution of Leve.rBy ELLIOTT FEINBERG, D.]Anterior teeth that exhibit marked al-veolar bone loss may often be retainedif the anatomical environment can bealtered to reduce stress caused by lever-age. Normally, there is a definite relation-ship between the portion of tooth that issupported by bone and the portion oftooth that is unsupported by bone. Withthe advent of periodontal disease, alveolarbone loss changes this relationship andthe increase in unsupported tooth struc-ture creates additional leverage on thealready diminished foundation. If thisratio is not corrected, the increase instress will tend to produce more rapidbone loss once the tolerance level of thepatient is passed. For this reason, splint-ing of the anterior teeth is not an answerto the problem unless it can also providean architectural environment that canfunction with less stress despite the ex-treme loss of alveolar bone.In order to produce a better ratio be-tween the two lever arms, it becomesnecessary to either increase the supportedtooth portion or decrease the unsupportedtooth length. Either of these changeswould result in a relationship whichwould have greater mechanical efficiencyand give nature abetter chance to main-tain the finished restorations. Since it isimpractical to consider raising the al-veolar bone level, the only practical ap-proach can be to decrease the length ofunsupported tooth structure. Figure 1demonstrates the mechanical advantagethat can be obtained by shortening thetooth.During the preparation stage moretooth structure is removed from the in-cisal edge than will later be replaced. Thismakes it necessary to evaluate the newl"ig. 2-The tuuth has been prepured sothat the finished restoration will replacefar less length on the incisal than was re-mo~'ed. The shoulder has been raisedfrom the dotted line to the new position.age for Anterior Teeth);8., Scarsdale, New YorkFig. I-By shortening the clinical crown,the relationship of A' to B' has a greatermechanical advantage than the originallever arms of A to B and will be sub-jected to far less leverage stress.length of clinical crown from an estheticas well as functional standpoint. It isimperative that the size of the new toothprovide enough space for proper shapeand form as well as adequate area fordefinite embrasure spaces. It is usuallybest to have as the end result a jacket or-,~ ,~~,-,--,c '--~ 1 -y--- "
  2. restoration whose clinical crown is ap-proximately the same size as the patient'sQriginal anatomical crown. This is easilyaccomplished by raising the gingival linea corresponding amount, a small problemdue to marked alveolar recession. Perio-dontal therapy should be instituted priorto this step as it always is more desirableto work with healthy rather than diseasedtissue for more lasting results.The application of these stated prin-ciples results in mechanically raising theentire clinical crown in the maxillaryarch. This automatically reduces theamount of overbite and diminishes thetraumatic effect that is usually associatedduring protrusive movements. Fig. 3shows a mouth that has been fully re-stored. Note that although the verticaldimension has not been altered, the me-chanical relationship of the anterior teethhas been changed to eliminate unduestress. The length of the finished restora-tions is approximately the size of the or-iginal anatomical crowns, not the clinicalcrown that the patient had before treat-ment.Fig. 3-A and B3-A Before TreatmentFig. 4-A and BShortening of the length of unsupportedtooth has changed the relationship andcreated an environment that is compatiblewith oral health.The same principles are applicable tocases having deep overbites which mayrequire restorations for reasons other thanperiodontal breakdown-such as estheticconsiderations. The resultant change inthe centric architecture will eliminate "ex-3-B After all teeth were jacketed ex-cept lower anteriors.
  3. Clinical experience demonstrates that theuse of endodontic therapy with this typeof architectural preparation produces ex-cellent chance of success in a well or-ganized restorative approach.-SUMMARY -The philosophy of mechanically redis-tributing leverage forces on anterior teethduring the preparation stage is a definiteaid in creating an architectural environ-nient that affords nature the opportunityto maintain teeth that have been severelyperiodontally damaged. When applied inconjunction with routine periodontal ther-apy, this technique is a clinically effectiveaddition to the restorative armamenta-rium.cess pressure and make it possible to useporcelain jacket restorations rather thanindividual veneer crowns since breakagewill no longer be a factor.Decreasing the length of unsupportedtooth structure may sometimes have to becombined with endodontic therapy in or-der to obtain the greatest chance formaintaining these "questionable" teeth.Cases that show marked labial drifting ofthe upper anterior teeth usually have ac-companying degrees of extrusion.After the teeth are orthodontically re-turned to a more advantageous position,there is usually an even greater degree ofoverbite. In such instances, it is moreprudent to institute preventive root ther-apy at this time rather than either com-promise the length of the preparation, oroverprepare the tooth in a manner thatwill cause loss of vitality and possible in-convenience to the patient in the future.ELLIOT FEINBERG, D.D.S.Scarsdale, New YorkFig. S-A and BFive years after treatment showing theability of the teeth to resist further break-down once the leverage factors aremechanically oriented.
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