On the influence of superstructure connection on implant preload: a methodological and clinical study

In a combined in vitro and in vivo study strain gauges were used to register the deformation in two terminal implant abutment cylinders, when connecting three different prosthetic appliances. The prosthetic constructions were placed on the abutments and fastened in vitro and in vivo by using different torque sequences. Furthermore, in the in vitro situation the three medial abutments were replaced by abutments which were 100 microns shorter. The results show that even if the prosthetic constructions were judged to have a good clinical fit, relatively large External Preloads were registered both in vitro and in vivo. No significant differences in axial force or in bending movement were found between the torque sequences in vivo. There were, however, significant differences in axial force as well as in bending moment in the in vitro experiment. When the shorter medial abutments were used in vitro, a change in the axial force of approximately 200 N was registered. The results confirm that the methodological approach used in this study is valid when evaluating preloads.