Vertical load distribution on a three-unit prosthesis supported by a natural tooth and a single Brånemark implant. An in vivo study.

In vivo bite forces, implant axial forces and bending moments were measured on 5 patients with fixed posterior prostheses supported by a natural tooth and a single Brånemark implant. The results demonstrate that the vertical loads applied to the prostheses are shared between the tooth and the implant. The maximum bending moment transferred to the implant (10-15 N.cm) was well below the acceptable load limits for the mechanical components (50-60 N.cm), even at bite forces exceeding 100 N. The main reason for this load sharing seems to be the inherent bending flexibility of the implant screw joint, which matches the axial flexibility of the periodontal ligament of the tooth.