Biomechanical Evaluation of Tooth- and Implant-Supported Fixed Dental Prostheses with Various Nonrigid Connector Positions: A Finite Element Analysis

Purpose: In the tooth- and implant-supported fixed dental prosthesis (FDP), rigid and nonrigid connector (NRC) designs have been preferred by clinicians for many years. The aim of this study was to analyze the stress distribution on the connecting areas of the superstructure and supporting structure of the tooth- and implant-supported FDP designs under both static vertical and oblique occlusal loads. Materials and Methods: Four 2D finite element analysis (FEA) models were prepared presuming that the first and second molars were missing, and that the implant (3.80-mm diameter × 13-mm length) was placed in the second molar NRC design and patrix-matrix position supported by teeth/implants. Nonlinear contact elements were used to simulate a realistic interface fixation within the implant system and the sliding function of the NRC. Supporting periodontal ligament and alveolar bone (cortical and trabecular) were also modeled. Linear static analysis was performed on the prepared 2D solid models with a total masticatory force of 250 N (50 N for premolar, 100 N for first molar, 100 N for second molar), 0° (at a right angle) and 30° to the long axis of the supports. The maximum equivalent Von Mises (VMMax) was analyzed around the supporting teeth/implant and connector areas on tooth- and implant-supported FDP. Results: The simulated results indicated that the highest level of VMMax (400.377 MPa) was observed on the NRC with the matrix positioned on the implant site of tooth- and implant-supported FDP under vertical occlusal load. The highest level of VMMax (392.8 MPa) under oblique occlusal load was also observed on the same model; however, the lowest VMMax value around implants was observed with the NRC when the patrix was positioned on the implant site of the FDP. Under vertical occlusal loads, in designs where the NRC was placed on the implant site, the stress formed around the implant decreased when compared to the designs where the NRCs were positioned on the tooth site. Conclusions: The efficiency of the NRC exhibited varying behavior depending on the direction of the load applied. The use of the patrix part of the NRC on the implant site may be more efficient in reducing the stress formation around the implant.