Finite element analysis of an implant-assisted removable partial denture with different positions of the rest arm

When implants are incorporated into an existing removable partial denture, fracture of the acrylic base often occurs. The aim of this study is to analyse the effects of the rest arm position on an implant-assisted removable partial denture using finite element analysis (FEA). A Faro Arm scan was used to extract the geometrical data of a human partially edentulous mandible. A standard plus regular neck (4.8 x 12 mm) Straumann implant and titanium matrix, tooth roots and periodontal ligaments were modelled using a combination of reverse engineering in Rapidform XOR2 and solid modelling using the Solid Works CAD program. The model incorporated a removable partial denture (RPD) and was loaded with realistic bilateral forces. The commercial FEA program ANSYS Workbench 14.0 was used to analyse the stress and strain distributions in the implant assisted RPD and in the metal framework. It is found that moving the position of the rest arm from the mesial to distal side of abutment teeth improves the stress distribution in the metal framework and acrylic denture base structures. The metal frame work and acrylic structures were subjected to lower stresses in an implant-assisted removable partial denture (IARPD) with a distal arm design compared to an IARPD with a mesial arm design.