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issue 2016 — 37 Esthetic and Restorative Dentistry Article Dahl’s concept and controlling the vertical dimension of occlusion The idea of increasing the vertical dimen- sionofocclusion(VDO)totreatorrestore patients with abnormal tooth wear has been described and applied for a long time;oneofthefirstclinicianstopromote this technique was Dahl, who published manyarticles onthistopic.15 His approach wastouseametalappliancetoelevatethe occlusion and allow teeth to move pas- sively until they are again in occlusion and thencreatespacetorestoretheteethsta- bilized by the appliance.15 The dental movementsareintendedtooccurbycom- bined supra-eruption of occlusally free teethtogetherwithsimultaneousalveolar growth and intrusion ofteeth maintaining contacts.Itwasshownthatsuchphenom- enawouldoccurinasignificantproportion of patients treated according to this con- cept16 and the outcomes of such treat- ment have been corroborated by several recent papers and review articles.15–19 In- creasing the VDO is a key parameter for reversing and preventing the conse- quences of pathological wear and erosion.20–25 The passive eruption that ac- companiesthecontinuoustissuedestruc- tion and loss, tremendously restricts the spaceavailableforrestorations,whichdue to their limited thickness, would be very fragile or otherwise require unnecessary removal of the residual tooth structure. Recent clinical reports have largely vali- dated this treatment approach.23–25 Treatment outline and restorative options The decision regarding the optimal restorative choice is usually based on the pre-existingdentalcondition(presenceof decay,restoration,vitalornonvitalstatus), as well as the amount and localization of tissue loss. This means that various restorative options haveto be considered and that treatment planning is highly in- dividual (tooth-specific). Thetherapeutic scheme is logicallyori- ented toward re-establishing first proper length of the central incisors and anterior guidance, governing thereafter the new VDO. Proper anteriortooth anatomy and functionaredesignedaccordingtoobjec- tiveestheticguidelines,26 existingandfor- mer tooth anatomy, as well as functional and phonetic components. The first step entails producing study casts in the form of a partial (in the case of moderate pos- teriortissue loss) orfull-mouth wax-up (in the case of advanced generalized tooth wear or erosion; Fig. 1). — Direct composite option Thedirectcompositeoptionislogicallyin- dicatedforallformsof moderatetointer- mediate tissue loss or destruction.13–16 Amongthe benefits of a direct composite restoration are its highlyconservative ap- proach, the ability to replace or reshape small portions of the tooth, reparability, simplified replacement and relatively lim- ited cost (Fig. 2). Conversely, it is more techniquesensitiveandmightresultinthin layers of material over some surfaces, placing them mechanically at risk. When using a sculpting technique, proper anatomy can be created also with a direct technique, favoring the selection of a highly filled material with a firm consis- tency.27–29 In the case illustrating this treatmentmodality,ahighlyfilledhomog- enous nanohybrid material (inspiro, Edel- weiss DR) was used owing to its firm con- sistency,favorableforfree-handsculpting and modeling (Figs. 2f–l). — Indirect composite option The indirect option is logically preferred whenlargerrestorationsortissuedestruc- tion of a greaterseverityis present. It also provides greater control of the anatomy and occlusion in complex or advanced cases. Nevertheless, one should not neg- lect the direct option only in favor of this last parameter, as occlusion seems not to playa majorrole in the origin of parafunc- tion.4,5,30–32 Sincedirectandindirecttech- niques can be used together to treat the same patient, when indirect restorations are chosen, they have to be fabricated first, at the new VDO, and then direct composites placed. — Material selection Today,thedebateaboutwhetherceramics or composite is best indicated for such restorations is sometimes based on per- sonal experience and belief, rather than on scientific or clinical evidence. The rather abundant clinical literature dealing withtheclinicalbehaviorofcompositeand ceramic inlays and onlays has not shown a major advantage of either material.33, 34 I clearly favor composite in the context of tooth wear. Were ceramics to be cho- sen, the Empress material (Ivoclar Vi- vadent), which has shown limited annual failure rates,35 and, of course, today’s new lithium disilicate pressed ceramic (IPS e.max Press, Ivoclar Vivadent), with improved flexural strength and fatigue resistance,36 would be considered the best choice. Longevity of restorations placed to correct severe tooth wear and erosion Clinical studies have demonstrated that the performance of composite in the treatment of advanced tooth wear is ad- equateandthatpartialfracturesrepresent themostlikelycomplication.Thesecanbe correctedbyarepairoruncomplicatedre- placementoftherestoration.37–39 Theten- year survival rate of porcelain-fused-to- metal crowns has been proved to be slightly superior to that of composite restorations, but with much more severe complications: Porcelain-fused-to-metal failures led mainly to endodontic treat- ments or to extractions, while composite failures or fractures could be either re- paired or replaced.40 This again demon- strates the reason the conservative and adhesive approach is favored for treating all kinds of mild to moderate forms of tooth wear and erosion. Conclusion Theincidenceoftoothwearrepresentsan increasing concern for the dental team and has multifactorial origins. Behavioral changes,anunbalanceddiet,variousmed- ical conditions and medications inducing acid reflux or influencing salivary compo- sition and flow rate trigger erosion. In ad- dition, awake and sleep bruxism are wide- spread functional disorders that cause severe abrasion. It is then increasingly im- portant to diagnose early signs of tooth wearsothatproperpreventiveand,ifnec- essary, restorative measures are taken, with the focus on biomechanics and long- term tissue preservation. Acknowledgments IwouldliketothankSergeErpen(OralPro, Geneva,Switzerland)forthefabricationof the wax-ups presented in Figures 2d and f. Article_Dietschi_00-00.qxp_Layout 1 02.03.16 20:47 Seite 2 Article_Dietschi_00-00.qxp_Layout 102.03.1620:47 Seite 2