A Comparative Finite Element Analysis of the Effect of Dynamic Forces on Narrow and Wide Implants in Kennedy’s Class 1 Mandibular Implant Supported Cast Partial Denture

Abstract

Background: Implant-assisted removable partial dentures (IARPDs) have emerged as a predictable treatment option for restoring mandibular Kennedy Class I distal extension edentulism by improving prosthesis support, stability, and load distribution. Among the factors influencing their biomechanical performance, implant diameter plays a crucial role in stress transmission to the surrounding bone and prosthetic components. This study evaluated the biomechanical behaviour of narrow and wide diameter implants supporting mandibular implant-assisted distal extension cast partial dentures under dynamic loading conditions using three-dimensional finite element analysis (FEA).  Materials and Methods: Two three-dimensional finite element models of mandibular Kennedy Class I arches restored with implant-assisted cast partial dentures were constructed. Model 1 incorporated narrow diameter implants (3.5 × 11.5 mm), whereas Model 2 incorporated wide diameter implants (5.0 × 10 mm). Both models were standardized with identical prosthesis design, attachment system, material properties, and loading conditions. Dynamic cyclic loading of 125,000 cycles was simulated using vertical (150 N) and oblique (100 N) occlusal forces. Maximum prosthesis displacement and von Mises stress distribution in the implant, peri-implant bone, prosthetic framework, denture base, artificial teeth, and abutment teeth were analysed.  Results: The narrow implant model demonstrated lower prosthesis displacement (0.16279 mm) than the wide implant model (0.25882 mm). The overall maximum von Mises stress was also lower in the narrow implant model (290.49 MPa) compared with the wide implant model (310.19 MPa). Stress concentrations within cortical and cancellous bone were reduced around narrow diameter implants, while the wide implant model exhibited greater stress transfer to the prosthetic components.  Conclusion: Within the limitations of this finite element study, narrow diameter implants demonstrated more favorable biomechanical behaviour by reducing prosthesis displacement and promoting balanced stress distribution under dynamic loading conditions. These findings suggest that narrow diameter implants may be a viable option for implant-assisted distal extension removable partial dentures when appropriate case selection and prosthetic design are employed.