Clinical outcomes and mechanical evaluation of patient-specific mandibular reconstruction following tumor resection: a retrospective study with finite element analysis

Mandibular defects most frequently result from ablative oncologic surgery and pose major functional and esthetic challenges. While vascularized osseous free flaps remain the gold-standard treatment, patient-specific implants (PSIs) fabricated by three-dimensional (3D) printing are an increasingly popular alternative. PSIs provide superior anatomical conformity and improved cosmetic outcomes, yet their long-term mechanical reliability and fatigue resistance remain unclear. This study aimed to evaluate both the biomechanical performance and clinical outcomes of 3D-printed PSIs for mandibular reconstruction. This retrospective study analyzed nine patients who underwent mandibular reconstruction with PSIs at Seoul National University Dental Hospital. Clinical outcomes and complications were reviewed at final follow-up (mean 36.1 ± 17.3 months; range, 5.5–63.9 months). Reconstruction plates were categorized into two types: Non-Filling Contour Plate (NFCP) and Defect-Filling Mesh Plate (DFMP). Finite element analysis (FEA) was performed on representative cases to assess stress distribution and fatigue behavior under physiological loading. During a mean follow-up of 36.1 months, two fractures occurred (22%): one NFCP at 34 months and one DFMP at 20 months, with both exhibiting segmental defects. FEA showed deformation of 2.01 mm in NFCP, 2.20 mm in DFMP, and 1.45 mm in modified DFMP. Peak stress was 683.3 MPa for NFCP, 378.2 MPa for DFMP and 498.8 MPa for modified DFMP, with DFMP showing mesh stress (156.6 MPa) exceeding local strength (68.2 MPa). NFCP fatigue analysis predicted ~ 184,000 cycles (≈ 3 months at maximal load), equivalent to 6–21 months under physiologic loading. Modified DFMP reduced mesh stress to 41.3 MPa. PSIs showed favorable clinical outcomes with excellent anatomical fit. Distinct failure mechanisms underscore the importance of fatigue life assessment, and design optimization like mesh repositioning may improve reliability for long-term use in oncologic mandibular reconstruction. Retrospectively registered.