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52 — issue 2016 Esthetic and Restorative Dentistry Article SMILE ANALYSIS — Converting digital designs into the final smile, Part 2 — Lee Culp, certified dental technician, is an adjunct professor at the Graduate Prosthetics Depart- ment of the University of North Carolina at Chapel Hill School of Dentistry in the U.S. He is among the leading devel- opers of many materials, prod- ucts and techniques used in dentistry today, and holds numerous patents. His writing, photography and teaching style have brought him inter- national recognition in digital dentistry, dental ceramics and functional esthetics. — Prof. Edward A. McLaren, D.D.S., is the director of the University of California, Los Angeles Center for Esthetic Dentistry in the U.S. He maintains a private practice in Los Angeles. “The way anterior and posterior teeth have been analyzed and characterized for the last 50 years has not been effective, as some of those methods have correlated the shape and morphology of the teeth to the shape and proportion of the head.” Introduction Thefabricationofrestorationshasentered a newtechnological age, movingfrom 2-D to 3-D. Restoration design—whether it is a framework,full-mouthrehabilitationorall- ceramic—now can be completed on com- puter.1 Thisarticle,thesecondinatwo-part series (the first part of which appeared in thefirstissueoftheClinicalMasters™mag- azine),addressestoothanatomy,morphol- ogyandthevariouslaboratoryapplications for digital design. Teeth are very difficult to recreate. The wayanteriorandposteriorteethhavebeen analyzed and characterized for the last 50 years has not been effective, as some of those methods have correlated the shape and morphology of the teeth to the shape and proportion of the head. However, in- dividuals with a square head do not neces- sarilyhave squareteeth; rounder-faced in- dividuals do not necessarily have round teeth,etc.Therearenosex-specificoreth- nic differences between teeth.2 The American Academy of Cosmetic Dentistry has published guidelines3 on the artisticparametersofsmiledesign,withthe goal of estheticallyreplicating nature. Ob- servation is fundamental to this endeavor, asisatrueunderstandingofpatientexpec- tations. In a very pleasing smile arrangement, the maxillarycentral incisorstilt in,the laterals tilt in slightly more, and the canines tilt in. In the mandibular arch, the anterior teeth tilt out slightly, while the canines tilt in (Fig. 1). There are three planes of a tooth and three shapes of the labial surfaces of thetooth:convex,flatandconcave.There are different tooth shapes: round on the mesial, round on the distal, square on the mesial, square onthe distal, and square on themesialanddistal.4 Whilethetrendmay be to create symmetrical inclinations be- tweentheteeth,tooth inclinations do not havetomatchtoachievenaturalesthetics. Toothshapeandproportionarecontrolled byrootshape,rootrotation,bone,andtis- sue preparation. The midline’s facial har- monysignificantlyaffectstoothesthetics. When the midline matches (e.g., height of contour to the mesial aspect, discrepan- cies regarding other esthetic aspects be- come insignificant. When two teeth are identical in length, angulation, midline, mesiodistal contour, and gingival sculpt- ing, the irregularities of the surrounding teeth do not detract from the overall es- thetics (Fig. 2). However, with some pa- tients, a closer examination of the sur- rounding teeth shows one is more square andthecontralateralisrounder;onetooth is tilted in and the other is not tilted (Fig. 2).5–7 Tooth anatomy All tooth anatomy is imparted in the front of the tooth, but what constitutes the front of the tooth has to be clearly iden- tifiedanddefined.Thisispredicatedonun- derstanding where the contacts and em- brasures should be positioned relative to proper tooth anatomy. Embrasures must be properly angled, as well as opened mesially or distally, depending upon the anatomical buildup that is required. Once — Dr. Lida C. Swann, D.D.S., is a clinical assistant professor at the Graduate Prosthetics Department of the University of North Carolina at Chapel Hill School of Dentistry. Article_McLaren_00-00.qxp_Layout 1 02.03.16 20:49 Seite 1 Article_McLaren_00-00.qxp_Layout 102.03.1620:49 Seite 1