Biomechanical Behaviour of Simulated External Cervical Resorption Lesions With Varying 3D Extent Before and After Restoration: Finite Element Analysis Study

This study investigated the biomechanical behaviour of simulated external cervical resorption (ECR) lesions of varying 3D extent, before and after restoration, using finite element analysis (FEA). Seven maxillary incisors were modelled, representing Patel's classification stages: Group 1–2Bp, 2–2Cp, 3–2Cd, 4–3 Bd, 5–3Cd, 6–3Bp and 7–Control. ECR lesions were restored using Biodentine, with endodontic treatment when the pulp was involved. CBCT scans were used to generate 3D models, and a 240 N bite force was applied to evaluate stress via Von Mises and principal stress values. Pre‐treatment, all ECR lesions showed concentrated stress, highest in Group 3Bp (538.11 MPa), correlating directly with lesion height, circumferential spread and pulp proximity. Post‐treatment, biodentine reduced stress and improved the safety factor (SF), although most groups still had a failure index > 1, indicating residual fracture risk. Pulp involvement had the greatest biomechanical impact, highlighting the importance of early detection and classification‐based treatment planning.