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cosmetic dentistry_ beauty & science International Edition

special _ digital smile design I tissue on the articulator. After simulating the final outcome with respect to the rest of the face, the GPS digital facebow will position the maxillary cast onthearticulatorwiththeexactpitch,yawandrow of the photograph to reproduce the virtual wax-up on provisional and final restorations. The M ruler guides the wax-up of the future smile. This process is actually the easiest way to transmit the entire aesthetic data concerning the facial soft tissue to the laboratory. _Project realisation The model’s wax-up was used to fabricate a preparation guide8 to perform minimally invasive preparation, controlling ceramic thickness and maintaining the structural integrity of the tooth.8, 9 A silicone impression of the wax-up was taken with Sil-TechPutty(IvoclarVivadent)andtheimpression was filled with Luxatemp provisional material in shadeA2(Luxatemp,DMG,USA)andthenrelinedto the prepared teeth in order to create a mock-up. Once the wax-up had been used to create a precise mock-up, the mock-up was scanned and constituted the ghost guide for the CEREC system (Sirona) to project (Figs. 11a–c) and produce chair- sidetenmaxillaryandmandibularveneersusingIPS Empress CAD blocks (Ivoclar Vivadent). The final restorations were successively stained, glazed and cementedwithshadeA3Variolink(IvoclarVivadent; Figs. 12a & b). At the end of treatment, the smile line had been corrected to follow the lower lip line contour, and the final smile results were in harmony with the patient’s face. Both maxillary central incisors were dominant and had been designed to the specific width and length by the GPS program to suit the patient’s face. The final aesthetic outcome fulfilled the patient’s expectations, and an improved smile andfacialappearancewereachieved(Figs.13a&b). _Discussion By using a simple preoperative facial photo- graph of the patient, the dental practitioner can diagnose, create a treatment plan, and produce with precision a virtual wax-up and laboratory prescription in less than 10 minutes. The software in this case uses the M Ruler to determine the best smile for the patient. The Golden Proportion Rule, or Divine Rule, rep- resentsaratioof1:1.618.Thisratiohasbeenusedin a multitude of applications for many years, and is wellknownintheartsandarchitecture,datingback manycenturies.Overthecourseoftime,thisGolden Proportion Rule has been applied to facial aesthet- ics and dentistry to provide mathematical guide- lines for the creation of pleasing and aesthetic smiles by the determination of the appropriate proportions of the central and lateral incisors, and the canines in the smile. However, many authors have observed that natural teeth do not follow the GoldenProportionRuleforthedisplayofteeth8,10,11 and this rule cannot be universally applied to all patients. In order to achieve a good aesthetic result, the ratio of the Golden Proportion Rule must be changed or adapted for each patient. ThismodifiedGoldenProportionRuleisachieved by application of a mathematical formula relating to the inter-molar distance of each patient, repre- senting the width of the arch and the width of the central incisors to determine the correct balance for the teeth displayed within that arch to create a pleasing smile.5 Fig. 10_Once the wax-up has been calibrated to the 2-D virtual simulation, the realisation of the project is very easy and will respect the preprogrammed aesthetics. Individualization of the final ceramics is possible. Figs. 11a–c_Prepared teeth and project (a) are scanned using the chairside CEREC Software 4.2. The wax-up (b) is scanned and used in “ghost” modality to guide the creation of the definitive restorations (c). These are milled with the CEREC MC XL milling unit. I 15cosmeticdentistry 1_2014 Fig. 11cFig. 11bFig. 11a Fig. 10Fig. 9b CDE0114_12-16_DelCorso 11.06.14 14:03 Seite 4