Comparative Evaluation of the Stresses Applied to the Bone, fixtures, and Abutments of Implant-Supported Fixed-Partial-Dentures with Different Long-Spans, After Cyclic Loading Using 3 Dimensional Finite-Element-Method Evaluation of implant-supported-FPDs

Objectives: The pattern of forces transmission and the stress distribution are very important in success or failure of implant-supported fixed-partial-dentures (ISFPD). The exact number of pontics between two implant abutments has always been debatable. The reliability of Ante’s law for ISFPDs is also questionable. The aim of this study was to evaluate the stresses applied to the bone and abutments of an ISFPD with two implants using 3D finite element method (3D FEM). Materials and Methods: In this study, a model with type 2 bone and two implants (Diameter: 4.1, Length: 12 mm, solid abutment, solid cover, ITI, Straumann, Switzerland) were simulated by Solidworks 2007 software. Three-unit, 4-unit, and 5-unit ISFPD models were designed in the software. Osseointegration was assumed 100% between implants and bone. For all three models, forces equivalent to 50, 100, and 150 N were respectively applied to the first premolar, the second premolar, and the first molar dynamically. The maximum Vonmisses stresses (VMS) and strain values (SV) were recorded. Results: The maximum VMS was seen in the bones around the crestal area of the cortical part in all three models. The maximum VMS applied in 5-unit model bone were higher than thoseof two other models. The maximum VMS in the abutments and fixtures of 5-unit model were higher than those of 3-unit and 4-unit ISFPDs. Conclusion: The VMS imposed in 5-unit ISFPD in type II bone were comparable with thoseof 3-unit and 4-unit ISFPDs. Of course, all the strains were in the bone endurance range. VMS in the abutments and fixturesof all three models were in the permanent-durability-range of the bone