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I 13 case report _ prosthodontic rehabilitation I CAD/CAM 1_2010 aleversystem,functionalloadisinverselyproportional to the length of the lever arm. Anterior teeth are under areducedfunctionalloadincomparisonwithposterior teeth. Porcelain-fused-to-metal restorations are com- monlyusedintheposteriorteethbecauseoftheirwell- documentedlong-termclinicaltrackrecordinanterior and posterior teeth.10–17 Newer zirconium-oxide-based materials are usually prescribed in the anterior region owingtotheirdemonstratedpromisingphysicalprop- erties18,19 and reasonable clinical longevity.20 In vitro studies also show that the wear of metal occlusal sur- faces against porcelain occlusal material is acceptable whentherearenobruxingactivities.21 This article describes the prosthodontic manage- ment of a mutilated dentition using high-strength zirconium-oxidecrowns. _Clinical report A 63-year-old fully dentate male patient presented withdiscolouredteethandmultipleareasoflossoftooth structure.Thepatientdesiredtherestorationoffunction and aesthetics. He presented clinically with defective restorations,insignificantlossofVDOandcompromised aesthetics(Figs.1–3).Thereweresignsoflossofenamel at the occlusal and labial surfaces of most of the teeth. Thepre-treatmentradiographwaswithinnormallimits (Fig.4).Inspiteoftheoverallcondition,thenaturalteeth were free of active dental caries and oral hygiene was good. An occlusal examination revealed a stable maxi- mal inter-cuspation position with insignificant centric relation to maximal inter-cuspation slide at the teeth level.Nopara-functionalhabitwasreported. A diagnostic dental wax-up on mounted maxillary and mandibular casts in a semi-adjustable articulator was performed (Hanau Wide-vue, Teledyne Waterpik; Fig. 5). The proportions of the anterior teeth were corrected to the estimated 0.618 width-to-height ra- tioofcentralincisorsusingthegoldenproportion22–25 asaguideline.Theresultsindicatedthatnoincreaseof VDO was needed at the incisal pin level in order to re- store proper incisal anatomy and anterior guidance. The overall treatment plan included placement of fixed, high-strength zirconium-oxide base restora- tionsinthemaxillaandmandible. Themaxillaryandmandibularteethwerepreparedin theusualmannerforcompletecoveragecrownrestora- tions(Figs.6&7).Themarginsofthetoothpreparations werepreparedatthegingivallevelundermagnification, and no gingival displacement procedures on the prepared teeth were necessary prior to definitive im- pressionmaking.High-viscosityvinylpolysiloxanema- terial(AquasilUltraHeavy,DENTSPLYDeTrey)wascare- fullyinjectedontoalltoothpreparations,ensuringthat allteethsurfacesincludingthemarginswererecorded. A stock tray loaded with putty material (Aquasil Putty, DENTSPLYDeTrey)wasseatedovertheentiredentalarch tomakethedefinitiveimpression.Ajawrelationrecord wasmadewithavinylpolysiloxanematerial(RegisilPB, DENTSPLYDeTrey).Themaxillaryandmandibulardefin- itivecastsweremountedinthecentreofthearticulator using standard settings.26,27 Provisional crown restora- tions (Luxatemp Automix, Zenith/DMG) were placed onthepreparedteethattheestablishedVDO. The development of the planned definitive crown restorationswascarriedoutusingCAD/CAM.Themax- illary and mandibular definitive casts (Figs. 8 & 9) were scanned (ZENO Scan, Wieland) and the crown copings were designed using a software programme (3Shape D700). The copings were milled in zirconium base ma- terial(ZENOZrBridge,Wieland)withamillingmachine (ZENO 4030 M1, Wieland; Fig. 10). The copings were Fig. 7_Completed mandibular anterior teeth preparations for full coverage restorations. Less than 1.5mm of tooth structure was removed at the cervical third, owing to smaller tooth size. Fig. 8_Definitive maxillary cast. No die-spacer was required in the CAD/CAM manufacturing process. Fig. 9_Definitive mandibular cast Tooth reduction was generally more conservative when compared with conventional porcelain- fused-to-metal restorations. Fig. 10_Coping milling machine ZENO 4030 M1 (Wieland). Fig. 10 Fig. 9Fig. 8Fig. 7