Finite element analysis of implant-assisted removable partial dentures: Framework design considerations

Statement of problem Connecting an acrylic resin base to both a metal framework and a rigidly fixed implant may affect the rotational displacement of the prosthesis during loading. Purpose The purpose of this finite element analysis study was to analyze the effect of connecting a denture base metal framework to an implant with the aim of decreasing the rotational movement of an implant-assisted removable partial denture. Material and methods A mesial occlusal rest direct retainer and a distal occlusal rest direct retainer were modeled and adapted to incorporate a modified denture base metal framework in the connection area for each model. The stress and deformation patterns of the prosthesis structure were determined using finite element analysis and compared for both situations. Results A maximum von Mises stress of 923 MPa was observed on the metal framework of the prosthesis with a mesial occlusal rest, and the maximum value was 1478 MPa for the distal occlusal rest. A maximum von Mises stress of 17 MPa occurred on the acrylic resin denture base for the mesial occlusal rest, and a maximum von Mises stress of 29 MPa occurred for the distal occlusal rest. Conclusions The distal occlusal rest direct retainer is stiffer than the mesial design and undergoes approximately 66% less deformation. The modified denture base framework with an I-bar and distal occlusal rest design provides more effective support to the acrylic resin structure.