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CAD/CAM - international magazine of digital dentistry

aesthetic restorations case report | 21CAD/CAM 2 2016 thepatientworetheexistingdenturethathadbeen relined with soft silicone. After a six-month healing period, a satisfactory level of osseointegration was achieved, without any signs of bone resorption or inflammation. The implants were uncovered and gingiva formers in- serted. Two weeks later, an impression was taken to transfer the position of the implants to the dental lab.Aftermodelfabrication,appropriateabutments were selected and adapted to achieve a common insert direction for the bridge (Fig. 1). Digital technology was used to manufacture the temporary bridge. The model was scanned with a Zenotec D800 lab scanner (Wieland Dental) and the temporary bridge was designed with the 3Shape dental design software. Milling was carried out in a Zenotec select S2 milling unit (Wieland Dental) using a PMMA material (Telio CAD). Framework fabrication Since the patient was satisfied with the shape and functionofthetemporaryrestoration,weuseditas thebaseforthefinalrestorationdesign.Thenatural wear facets that formed during the temporisation period should be reflected in the final restoration. A conventional impression of the oral situation was taken in the practice. In the lab, a model and a gingival mask were prepared and scanned. First, the working model together with the temporary bridge was digitalised. Then we scanned the model together with the abutments, the opposing jaw model and the bite registration. Finally, the abut- mentswerescannedindividuallyoneaftertheother because the abutment shoulders were located subgingivally and could therefore not be captured accurately enough with the model scan alone (Figs. 2a & b). CAD construction First,thepositionofthedigitisedmodelwasdefined in the design software according to the common insert direction of the abutments. In a second step, the shoulder lines of the abutments were marked and the thickness of the cement gap was defined. The shoulder line represents the “preparation margin” of the restoration. In this case, we set the cement gap to 0.2 mm and the cement space to 0.4mm.Thethicknessofthecementgapatthemar- ginalborderwassetto0.1mm.Fromourexperience, these settings result in an excellent accuracy of fit of the restoration on the model and in the patient’s mouth, eliminating the need for later adjustments. At the end, the design of the restoration was checked once more against the individual design parameters. If the wall thickness is lower than the minimum acceptable, the software will issue a warning and enable an automated remediation step. The final restoration was designed using the full-contour long-term temporary as a basis. The full contours of teeth 13 to 23 were reduced by 0.9 mm on the vestibular aspect to make space for the partial veneers (Figs. 3a & b). Theincisalborderwasleftfullycontouredasalarge numberoffunctionalmovementsoccurinthisarea. The fully contoured shapes of the posterior teeth and the palatal surfaces of the anterior teeth were left unaltered to ensure a maximum level of Figs. 3a & b: First, the restoration was designed in full contour and then cut back in the visible aesthetic region. Fig. 4: Nesting of the bridge framework in the CAM software. Fig. 3a Fig. 3b Fig. 4 22016

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