Finite element analysis of stress distribution after folded and single-layer fibular reconstruction with implant restoration for brown class Ⅱ mandibular defects

OBJECTIVE: This study aimed to compare the stress distribution after folded and single-layer fibular reconstruction with implant-supported restoration for Brown Class Ⅱ mandibular defects using finite element analysis (FEA), to provide a theoretical basis for selecting an optimal mandibular reconstruction strategy in clinical practice. METHODS: A healthy adult female volunteer from Bengbu Medical University underwent spiral computed tomography (CT) scans of the mandible and fibula. The CT data were imported into Mimics 21.0 software to reconstruct three-dimensional models of the intact mandible, dentition, and fibula. These models were further processed in Geomagic Studio 2014, Materialise 3-matic 18.0, and Exocad to establish FEA models of the intact mandible, as well as single-layer (Model A) and folded (Model B) fibular reconstruction with implant-supported restoration for Brown Class Ⅱ mandibular defects. The geometric models were then imported into Ansys 19.0 software for FEA to evaluate biomechanical characteristics and stress distribution patterns on implants, the reconstructed fibula, and surrounding bone tissues were compared between the two reconstruction methods. RESULTS: (1) Under identical loading conditions, stress concentration areas in the intact mandible were observed at the bilateral condylar necks, sigmoid notches, mandibular angles, and junctions between the mandibular body and ramus, with the maximum stress (57.627 MPa) located at the affected-side mandibular angle. (2) In Model A and Model B, the maximum stresses in the residual mandible were 82.619 MPa and 80.842 MPa, respectively, both at the affected-side mandibular angle, representing increases of 43.4% and 40.3% compared to the intact mandible (57.627 MPa). (3) The maximum stress in the reconstructed fibula was 65.31 MPa in Model B, which was lower than the 73.922 MPa in Model A. (4) The maximum stresses in implants 1, 2, and 3 were 19.496 MPa, 50.638 MPa, and 78.747 MPa in Model B, and 32.537 MPa, 99.558 MPa, and 123.14 MPa in Model A, all located at the implant necks. CONCLUSION: Compared with the single-layer fibular flap, the folded fibular flap is a superior choice for the reconstruction of Brown Class Ⅱ mandibular defects with subsequent implant restoration.