Effect of Tilted and Short Distal Implants on Axial Forces and Bending Moments in Implants Supporting Fixed Dental Prostheses: An In Vitro Study

Purpose: The aim of this study was to evaluate the axial forces (AFs) and bending moments (BMs) on implants supporting a fixed dental prosthesis (FDP) with a distal cantilever (10 mm) compared to an FDP supported by a tilted or short (7 mm instead of 13 mm) posterior implant by means of in vitro strain gauge measurements. Materials and Methods: Nine titanium Brånemark implants were placed in an edentulous composite mandible. The mechanical loading conditions were evaluated for the following three situations: (1) short distal implants supporting a cantilever, (2) long tilted distal implants, and (3) no distal implants supporting a cantilever. A vertical load of 50 N was applied at the first molar position, and the resultant AFs and BMs were measured for the three different situations, three different numbers of supporting implants (three, four, or five), and three different prosthesis materials (titanium, acrylic, and fiber-reinforced acrylic). Results: The mean BMs, as well as the maximum AFs and BMs, were significantly higher in the model with a cantilever compared to that having the tilted or short distal implants (P .001). There was no significant difference between the models with a distally tilted implant versus a short distal implant. Conclusion: The use of posterior implants reduced the AFs and BMs on implants supporting an FDP compared to that with a distal cantilever. No difference in mechanical loading was observed between short tilted distal implants.