On titanium frameworks and alternative impression techniques in implant dentistry.

Abstract

Purpose: The objectives of this thesis were to compare the clinical and material performance of implant-supported titanium frameworks with gold-alloy frameworks in the edentulous jaw and to test a digitized impression technique to optimize material characteristics and clinical and laboratory procedures.

Materials and methods: Two different kinds of laser-welded titanium frameworks and one type of digitized computer numeric controlled (CNC)-milled titanium framework for the edentulous jaw were evaluated and compared with gold-alloy frameworks in two clinical 5-year follow-up studies. The CNC frameworks were also evaluated and compared with gold-alloy frameworks in two experimental studies according to fit, preload, and surface roughness. Furthermore, a digitized photogrammetric technique for recording implant positions in the edentulous jaw was experimentally tested and compared with two conventional impression techniques.

Results: Laser-welded titanium frameworks had a lower success rate after 5 years in function than gold-alloy frameworks. The 5-year performance of CNC frameworks was similar to that of gold-alloy frameworks. The fit and precision of implant-supported CNC frameworks was significantly better compared with gold-alloy frameworks. Applications of veneering material did not significantly affect the fit of the titanium frameworks. The preload of CNC frameworks was similar to that of gold-alloy frameworks, both exhibiting significantly decreased preloads after repeated tightening. The preloads of titanium frameworks were similar before and after veneering. Unloaded milled titanium screw sites had significantly rougher surfaces than loaded sites, and loaded gold screws had rougher surfaces than unloaded. No correlation between surface of the screw joints and preload of veneered titanium frameworks was observed. The precision of photogrammetric impressions was comparable to that of conventional impression techniques.

Conclusions: Implant-supported CNC-milled titanium frameworks are a viable alternative to gold-alloy castings in the edentulous jaw, and because a digital platform is used to manufacture these titanium frameworks, photogrammetric impressions can be made.