Tilting of splinted implants for improved prosthodontic support: a two-dimensional finite element analysis.

STATEMENT OF PROBLEM: Presence of the maxillary sinus or the mental foramen may prevent implant treatment in the posterior maxilla or mandible. Tilting of distal implants supporting fixed restorations may be a valid treatment alternative. PURPOSE: The aim of this study was to evaluate if tilting of splinted implants affects stress distribution in the bone surrounding the implant cervix, and to investigate if the use of tilted implants as distal abutments is biomechanically superior to the use of distal cantilevers. MATERIAL AND METHODS: A 2-dimensional (2-D) model for finite element analysis was developed using two 13-mm implants splinted by a titanium beam, 16 x 3 mm. The implants were embedded in bone blocks, simulating different bone properties. A small crater was created in the marginal bone around the tilted implant to simulate physiologic bone remodeling. The model with a distal cantilever 7 mm long and a distal implant was compared to a model in which the distal implant (13 or 19 mm) was tilted 45 degrees and supported the distal end of the cantilever. A force of 50 N was applied via the beam. RESULTS: The stress at the most coronal bone-to-implant contact was identical irrespective of the angle of tilt, demonstrating that tilting of splinted implants does not result in increased stress. The cantilevered model showed that the use of cantilevers results in higher stress in the marginal bone around implants. This stress is reduced to "normal" levels when the cantilever arm is negated by the distal implant being apically inclined to support the distal end of the cantilever. Use of a longer implant only reduces the stress marginally. CONCLUSIONS: Within the limitations of this 2-D finite element analysis, it appears that distal tilting of implants splinted by fixed restorations does not increase bone stress compared to normally placed, vertical implants. There is a biomechanical advantage in using tilted distal implants rather than distal cantilever units.