Stress analysis of mandibular implant-supported overdenture retained with bar and ball attachments of different heights: A comparative finite element study

Abstract

Aim: To evaluate and compare stress distribution patterns in mandibular implant-supported overdenture retained with bar and ball attachment systems at two attachment heights (1 mm and 3 mm) using three-dimensional finite element analysis (FEA). Settings and Design: An in silico comparative three-dimensional finite element analysis study. Materials and Methods: Four three-dimensional finite element models of an edentulous mandible restored with two interforaminal bone-level implants (3.5 × 10 mm) were developed. The models incorporated bar attachments with heights of 1 mm (A1) and 3 mm (A2), and ball attachments with heights of 1 mm (B1) and 3 mm (B2). All materials were assumed to be homogeneous, isotropic, and linearly elastic. Complete osseointegration was simulated using bonded contact conditions. A mesh convergence test was performed, and mesh refinement continued until the change in peak von Mises stress between successive mesh refinements was <5%. A static vertical load of 100 N was applied at the central occlusal fossa of the first molar under unilateral and bilateral loading conditions. Stress distribution was evaluated qualitatively and quantitatively using von Mises stress analysis. Statistical Analysis Used: No statistical analysis was performed. Stress distribution was compared descriptively using qualitative stress distribution patterns and quantitative von Mises stress values generated by the finite element models. Results: Under unilateral loading, stresses were concentrated predominantly on the working side, with the implant neck serving as the principal site of stress concentration. Increasing attachment height increased stress magnitudes in both bar and ball attachment systems under unilateral and bilateral loading conditions. Overall, stress concentrations were greatest at the implant neck, followed by the implant body and apical region. Cortical bone consistently exhibited higher stress values than cancellous bone across all models. Conclusion: Within the limitations of this finite element study, attachment height and splinting configuration influenced peri-implant stress distribution. Increased attachment height was associated with greater stress magnitudes in both attachment systems.