Finite element biomechanical comparison of bone-driven and occlusion-driven fibular flap positioning in lateral segmental mandibular reconstruction.

Abstract

<h4>Objective</h4>To evaluate, using finite-element analysis (FEA), the stress-strain state of mandibular bone and the bone component of a microvascular free fibula flap (FFF) reconstructing a lateral segmental mandibular defect, comparing two flap positions relevant to implant-supported fixed prosthetic rehabilitation.<h4>Materials and methods</h4>CT-derived three-dimensional models of a reconstructed mandible were generated in two geometries: (A) flap aligned with the inferior mandibular border and (B) flap positioned at the level of the alveolar crest. Each geometry received two endosseous implants and a fixed prosthesis and was subjected to representative masticatory loading (vertical/occlusal and anterior/incisal). Four FEA models (2 positions × 2 load cases) were analyzed, with two predefined regions of interest per model (distal and medial), each examined at the upper and lower margins.<h4>Results</h4>Compared with Model A (inferior mandibular border), Model B (alveolar crest) produced lower peak bone stresses in most analyzed regions (≈10-40% reduction) under mastication-representative static molar and incisal loads. The only exception was the medial-inferior margin under incisal loading, where stress increased markedly (8.96 vs 2.22 MPa; ∼4-fold). Under occlusal loading, medial-inferior stresses were <1 MPa in both models. Across both positioning scenarios, peak crestal bone von Mises stresses clustered near the implant neck (crestal bone); analyses were restricted to bone.<h4>Conclusion</h4>A higher (alveolar-crest) position of the bone component of the FFF yields a more favorable stress-strain environment and load distribution, supporting more favorable biomechanical conditions for osseointegration and long-term function.