A finite element analysis: Passive fit of implant supported dentures frameworks prepared with different materials and technics

The purpose of this finite element analysis (FEA) study is to compare the Von Mises stresses on linear and curved placed implant framework units, connectors and prosthetic screws of different framework materials of 5-unit screw retained fixed partial dentures (FPDs) with pier abutment. Two models were constructed and four framework materials were applied to Model I (linear) and Model II (curved); 1. Zirconia [ZrO2 (Z1,Z2)], 2. Chrome-cobalt alloy [Cr-Co (C1,C2)], 3. Palladium-silver alloy [Pd-Ag (P1,P2)], 4. Titanium alloy [Ti-6Al-4V (T1,T2)] simulated in COMSOL Multiphysics 4.2 environment. 100 N vertical and 200 N oblique forces were applied to each buccal tubercules. Maximum Von Mises stresses framework units, connectors and prosthetic screws were evaluated given by the software. Numeric results demonstrated that the stress values were higher in Model I. Since there is an increase in stress on second molar unit of the curved framework. For Model II only stresses belong to second molar unit was increased. When vertical forces were applied; the highest stress on FPDs framework was determined on Z1 group connectors. When oblique forces were applied, the highest stress was found on Z1 group canine and second premolar units. The highest stress of prosthetic screw was determined on P1 group. Palladium-silver frameworks give higher stress on prosthetic screws compared to other materials investigated in this study. Implant placement and framework materials effected the stresses on screw retained FPDs units, connectors and prosthetic screws. In both models the highest stresses were associated with the pier abutment. For all material groups zirconia had highest stress values on framework units and connectors because of their high elastic moduli. Moreover it is possible to decrease of the stresses by choosing CAD/CAM chrome-cobalt or titanium alloy instead of zirconia especially for linear placed implants which are 3th, 5th and 7th teeth location. Decreasing of the stresses may give better passive fit.