Finite element analysis to evaluate and compare stress distribution in fixed partial denture with pier abutment using rigid and non-rigid connector

Abstract

Statement of problem: Fixed partial dentures (FPDs) involving an intermediate pier abutment may be subjected to unfavorable biomechanical forces because of the differential movement of the supporting abutment teeth. The design and location of a nonrigid connector may influence the manner in which occlusal stresses are transferred through the prosthesis and supporting structures. Purpose: The purpose of this study was to evaluate the effect of rigid and nonrigid connector designs on stress distribution in a 5-unit FPD with an intermediate pier abutment using three-dimensional finite element analysis (FEA). Material and methods: A three-dimensional finite element model representing a 5-unit metal-ceramic FPD was developed using SAP2000 software (Computers & Structures, Inc.). The mandibular canine, second premolar, and second molar were modeled as abutment teeth, with the periodontal ligament (PDL) and surrounding cortical and trabecular bone incorporated into the model. Five prosthetic configurations were evaluated: 1 rigid design and 4 nonrigid designs, with the nonrigid connector positioned at the mesial aspect of the second molar, distal aspect of the second premolar, mesial aspect of the second premolar, or distal aspect of the canine. A static vertical occlusal load of 50 N was applied to the cusp regions. Three loading conditions were simulated: simultaneous loading of all abutment teeth to represent maximum centric occlusal contact, isolated loading of the canine to simulate an anterior contact, and isolated loading of the second molar to simulate a posterior contact. Stress distribution was evaluated according to von Mises stress criteria. Results: For all prosthetic designs and loading conditions, the highest stress concentrations occurred in the regions subjected to loading, with maximum values of approximately 2 MPa. Additional stress concentrations were observed at the connector regions and cervical areas of the abutment teeth, particularly around the pier abutment. Stress concentrations were also identified along the root surfaces and at the apical regions of the abutments. Among the nonrigid configurations, placement of the connector at the distal aspect of the second premolar reduced the area of maximum stress concentration around the pier abutment, particularly under isolated anterior and posterior loading conditions. Conclusions: Within the limitations of the finite element model, both the presence and location of a nonrigid connector influenced stress distribution in a 5-unit FPD supported by a pier abutment. Placement of the nonrigid connector at the distal aspect of the second premolar resulted in a more favorable stress distribution around the pier abutment than the other connector configurations evaluated. Clinical implications: The location of a nonrigid connector may be an important consideration when designing an FPD involving an intermediate pier abutment, particularly when the objective is to reduce localized stress concentration around the pier abutment.