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ePaper created 2017-03-17, 11:21:45 | version 1.38.0
| industry report implant restoration The synthesis of aesthetics, health and structural stability The advantages of using the Angulated Screw Channel (ASC) abutment system Author: Dr Chandur Wadhwani, USA Fig. 1 Fig. 2a Fig. 2b Fig. 3 Fig. 1: Failed, removed implant, cement extrusion is noted on multiple threads. Figs. 2a & b: The anterior teeth present a challenge to the screw-retained restoration unless an Angulated Screw Channel (ASC) abutment is used (a). In cases where the surgical placement is less than ideal, the ASC may help limit further compromise to the site (b). Fig. 3: The ASC shows the angle redirection of the screw access channel. Figs. 4a & b: Even with shallow margins and minimal cement (a), the elimination of cement extrusion still presents a clinical challenge (b). Fig. 5: The Nobel Biocare CAD/CAM software allows ideal screw access There are many reasons why cement-retained im- plant restorations gained popularity over the last few years, which can be attributed to aesthetics, ease of use and familiarity with cementation techniques. However, Pauletto, Gapski and others reported that cement excess was problematic; then Wilson’s study established a positive relationship between excess residual cement and peri-implantitis. Surveys on cements used for implant restorations indicated a diversity in material selection, applica- tion technique and volume. This suggested a lack of conformity and understanding of cement usage within the dental profession. To overcome the ce- ment problem, it became evident that improved understanding was required for cement material selection, abutment design and the determination of cement margin depths. Even with the very best in- tentions, however, residual excess cement can lead to disease, affecting the health of the implant/tissue interface and remains a dominant risk factor. site to be planned, then machine fabricated. The association of residual excess cement and peri- implantitis has resulted in the need to re-examine alternatives such as the screw-retained implant crown. For many implant systems, the ability to use a screw-retained implant restoration is limited to regions where the screw access channel emerges in an aesthetically ‘safe’ site. Usually the anterior maxilla and mandible present the greatest challenges, as the long axis of the im- plant often projects through the proposed incisal edge or even facial to the final restoration (Fig. 2a). Occasionally, when the surgeon places the implant in a compromised site—or the implant is inappro- priately placed—the traditional screw-retained im- plant restoration may seem to provide more of a challenge than a solution (Fig. 2b). Angulated Screw Channel saves the day An innovative solution to the off-axial implant is the Angulated Screw Channel (ASC) abutment system developed by Nobel Biocare (Fig. 3). With the ability to alter the screw channel up to 25 degrees, it elim- inates the need for cementation in the vast majority of cases like these. Fig. 4a Fig. 4b Fig. 5 36 CAD/CAM 1 2017