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ePaper created 2015-05-14, 11:05:01 | version 1.38.0
special _ smile analysis and smile design I The width-to-length ratio most often discussed in theliteratureisbetween75%and80%,butaesthetic smiles could demonstrate ratios between 70% and 75% or between 80% and 85% (Figs. 8–10).1 Thelengthofteethalsoaffectsaesthetics.Maxillary central incisors average between 10mm and 11mm in length. According to Magne, the average length of an unworn maxillary central to the cementoenamel junctionisslightlyover11mm.10 Theaestheticzonefor central incisor length, according to the authors, is be- tween 10.5mm and 12mm, with 11mm being a good starting point. Lateral incisors are between 1mm and a maximum of 2mm shorter than the central incisors, with the canines slightly shorter than the central inci- sorsbybetween0.5mmand1mm(Fig.11). Theinter-toothrelationship,orarchform,involves the golden proportion and position of tooth width. Although it is a good beginning, it does not reflect natural tooth proportions. Natural portions demon- strate a lateral incisor between 60% and 70% of the widthofthecentralincisor,andthisislargerthanthe golden proportion.11 However, a rule guiding propor- tions is that the canine and all teeth distal should be perceived to occupy less visual space (Fig. 12). An- other rule to help maintain proportions throughout thearchis1-2-3-4-5;thelateralincisoristwo-thirds of the central incisor and the canine is four-fifths of the lateral incisor, with some latitude within those spaces (Fig. 13). Finally, contact areas can be moved restoratively up to the root of the adjacent tooth. Beyond that, orthodontics is required (Fig. 14). _Creating a digital smile designed in Photoshop Although there are digital smile design services available to dentists for a fee, it is possible to use Photoshop CS5 software (Adobe Systems) to create and demonstrate for patients the proposed smile design treatments. It starts by creating tooth grids— predesigned tooth templates in different width-to- lengthratios(e.g.,75%central,80%central)thatcan be incorporated into a custom smile design based on patient characteristics. You can create as many dif- ferenttoothgridsasyoulikewithdifferenttoothpro- portions in the aesthetic zone. Once completed, you Figs. 8–10_Acceptable width-to- length ratios fall between 70% and 85%, with the ideal range between 80% and 85%. Fig. 11_An acceptable starting point for central incisors is 11mm in length, with lateral incisors 1–2mm shorter than the central incisors, and canines 0.5–1mm shorter than the central incisors for an aesthetic smile display. Fig. 12_The canines and other teeth distally located are visually perceived as occupying less space in an aesthetically pleasing smile. Fig. 13_A general rule for achieving proportionate smile design is that lateral incisors should measure two-thirds of the central incisors and canines four-fifths of the lateral incisors. Fig. 14_If feasible, the contact areas can be restoratively moved up to the root of the adjacent tooth. I 13CAD/CAM 2_2015 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14