Dr. Svoboda presents the results of an in vitro research project done to compare the Chamfer Margin design with the Reverse Margin design, in regard to their ability to prevent excess cement from going beyond the margins of the abutment. The trials were done under two crown cementation pressures and the margins tested were either 1/2 or 1 mm below the simulated gingiva. Results indicate that the Reverse Margin design was much better than the Chamfer Margin design at preventing or reducing the extension of cement beyond the margins. As well, reduced cementation pressure and reduced margin depth enhanced the effectiveness of both margin types. The current screw-in system of prosthesis installation exposes patients to implant-abutment and abutment-prosthesis misfits, and cantilevers for screw access that can amplify forces on misfit parts and make access to care difficult. The screw-in system of installation does not allow the clinician to consistently exploit the fit of the high precision parts made by today’s high-quality implant manufacturers. Cement-in prosthetics make it possible for the clinician to consistently optimize the fit of implant components and to narrow the profile of prosthetics to improve access to care. However, current systems can also cause subgingival cement and poor prosthesis margins. These research findings provide a way for dentists to gain the advantages of a cemented prostheses without the poor margins and submarginal cement. The use of Reverse Margin designs for the abutments and complimentary prosthetics, together with a low-pressure installation protocol seems to be the answer. Some clinical studies are underway, and the results appear to be consistent with those reported here. More clinical studies are needed. For more information, go to www.ReverseMargin.com. This research was done by Dr Svoboda in collaboration with Dr. Anit Sharma and Dr. Majid Zakari.
Understand why the Reverse Margin design prevents excess cement from going into the tissue spaces, while the Chamfer Margin does not.
Understand why low pressure installation results less submarginal cement
Understand why upward facing margins are easier to access and maintain than downward facing margins