Distribution of load in an oral prosthesis system: an in vitro study.

Although the long-term success of osseointegrated endosseous implants for the support of fixed dental prostheses has been reported, the increasingly routine and widespread use of implant-supported prostheses has led to problems associated with their structural integrity. To assess the service life of the components of the prosthetic system, a knowledge of the loads transmitted through the system is needed. This paper reports in vitro findings for forces and bending moments transmitted through the abutments from a fixed dental prosthesis to its supporting implants. The results have been compared to previous theoretical analyses that generally overestimate the maximum tensile forces. The effect of the length of distal cantilevers and of missing gold screws as the result of loosening or fracture is also considered. It is proposed that bending moments may play a larger role in failures than previously believed.

Tightening characteristics for screwed joints in osseointegrated dental implants.

The significance of tightening abutment screws and gold cylinders to osseointegrated fixtures with the correct torque is demonstrated, and a simple relationship between applied torque and screw preload is derived by use of mechanical engineering principles. The principles of a number of tightening methods are outlined and assessments made of their accuracy. The difference between optimum and design torque is highlighted. The necessity and means of achieving optimum torque to ensure a reliable joint in clinical practice is discussed.