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CAD/CAM - international magazine of digital dentistry, Italian Edition, No.1, 2016

1_201622 case report _ implant restorations the upper jaw, the occlusal rim was shaped in such a way that 2 mm of the edge was visible when the upper lip was in rest posi- tion. The lower edge of the rim was aligned parallel to the bipupillary plane and smooth- ly followed the curve of the lower lip when the patient smiled. On the maxillary rim, the midline, the smile line and the line of the canines were outlined. A facebow was used for the transfer of the maxillary position in relation to the base of the skull. Once all of the relevant ratios had been obtained, the models were mounted on the articulator (Fig. 5). The difficulty of this case was that we had to make allowance for the existing mandibular restoration in the design of the maxillary rehabilitation. The implant axes of the mandibular prosthesis in particular posed some problems. Shade selection was dictated by the mandibular restoration and, consequently, our room for decision-making was reduced to deciding on the shape of the teeth. To this end, a photograph of the patient as a young adult was useful, as it was her wish that the shape and size of her teeth Figs. 9 & 10_Grinding and smoothing of the primary structure made from zirconia in a milling unit using CAD/CAM technology. as they were when she was young should be re-established in the prosthetic recon- struction. With the aim to attain as perfect a prosthesis as possible and to make the most of the available space, we created a wax set- up using prefabricated denture teeth (SR Phonares II, Ivoclar Vivadent). _Primary structure A try-in of the set-up was performed to check the phonetics, aesthetics and occlu- sion (Fig. 6) and then a silicone key was cre- ated over the set-up. This acted as a guide in the subsequent working steps. In order to manufacture the primary structure, the four titanium abutments were customised (Fig. 7), the resulting abutments were scanned together with the model and set-up (dou- ble scan), and these datasets were imported into the design software. The CAD program proceeded to suggest the shape, height and angulation of the telescope crowns, which we adjusted and optimised as required (Fig. 8). The primary telescopes were milled from zirconia and sintered to their final density at 1,500 °C. After the accuracy of fit had been checked, the zirconia crowns were permanently bond- ed to the titanium abutments (Multilink Hy- brid Abutment, Ivoclar Vivadent). Finally, the zirconia telescopes were ad- justed using a laboratory turbine and paral- lelograph. The walls of the telescopes were given 2-degree incline and smoothed using appropriate diamond grinding tools and suf- ficient water-cooling (Figs. 9 & 10). _Secondary structure The primary crowns could now be pre- pared for manufacturing the secondary crowns by means of the electroforming technique. For this purpose, the zirconia surfaces were covered in a thin coating of Fig. 11_Intra-oral bonding of the electroformed secondary structure with the tertiary structure. Fig. 9 Fig. 10 Fig. 11

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