cosmetic dentistry_ beauty & science

16 I I special _ prosthetic techniques cosmeticdentistry 4_2011 alsoconsidered.Today,takingallofthesefactorsinto account, one will most likely derive some sort of hy- brid shape based on one of the three original basic shapes. Theconceptofthethreebasicshapeswithregard to the labial effect of a tooth can be demonstrated when viewed from the incisal perspective. A study byYammamotodemonstratesthiswell(Figs.13–15). From the incisal perspective, the relative flatness of the square shape, the concavity of the triangular shapeandtheconvexityoftheovoidshapeisappar- ent. Another decisive aspect of a successful natural reproduction is the design of the marginal ridges or lineangles,whichhasaneffectonthe3-Dappearance ofthetooth. Besidestheshapeandthewidthofthetoothcrown, thewidthoftherootisalsoadecisivefactor.Uptonow, I have restricted the consideration of the tooth to the labial and incisal view. In order to be able to replicate the 3-D appearance of the tooth, we must also con- sider the labial curvature of the tooth (Figs. 16–18). From this point of view, the incisal triangle features can also be divided into the three basic components. For each individual case, it is then necessary to derive therespectivehybridshape. Afterthishasbeenconsidered,thefollowingtypes canbederivedfromthemesialview: Theovalanatomytype _Thetwowell-developedlabialmarginalridgesarethe keycharacteristicfeatureofthisanatomytype. _A strong labial depression and a wide labial transi- tional surface are present. The difference between the mesio- and the disto-approximal surface is no- ticeable.Thedistalfaceiswiderthanthemesial. _The growth lobes are generally not very prominent withthistoothshapetype. Thethree-angledanatomytype _The mesial and distal marginal ridges are again dis- tinctbutnotasstrongaswiththeovalanatomytype. _The labial surfaces are relatively wide, without a no- ticeable difference in width between the mesial and thedistal. _Thelabialandproximalgrowthlobesareprominent. Thesquareanatomytype _Thecharacteristicfeatureofthisanatomytypeisthe indistinct marginal ridges, which can sometimes causearatherplainlook. _A well-developed central marginal ridge is present, which appears quite prominent when viewed from theincisaledge. _Thelabialandapproximaldepressionsaresomewhat stronglydeveloped,althoughnotasstronglyaswith thetriangulartype. The marginal ridges or line angles develop in the sulcus and run parallel to the basic outer shape of the toothtowardstheincisaledge.Attheincisalaspect,the progressionofthemarginalridgesdiffersbetweenun- abradedjuvenileteethandwornagedteeth(Figs.19–24). These different morphological characteristics are evident in the case of adjacent teeth, which makes the Fig. 19_Twelve-year-old patient with nicely indented incisal edges. Fig. 20_Comparison of a 30-year-old patient with abraded incisal edges ... Fig. 21_... and a 50-year-old patient with strongly worn incisal edges. Fig. 22_Mandibulary anteriors of a 12-year-old patient with strong mamelons. Fig. 23_Mandibulary anteriors of a 30-year-old patient. Fig. 24_A set of lower anteriors with strong occlusal wear facets. Fig. 25_The nose base determines the width of the upper anterior teeth (Gerber). Fig. 26_The average nose type correlates with the average width of anterior acrylic teeth. Fig. 27_A narrow nose base is an indication of slender anteriors. Fig. 25 Fig. 26 Fig. 27 Fig. 19 Fig. 20 Fig. 21 Fig. 22 Fig. 23 Fig. 24