Effect of Root Perforation and Bone Defect on Stress Distribution and Displacement of Maxillary First Premolars: Biomechanical Decoupling Effect of MTA Restoration.

Introduction: This study used finite element analysis to investigate the effects of root perforation and secondary bone defects on the stress distribution and displacement in maxillary first premolars and to evaluate the efficacy of mineral trioxide aggregate (MTA) in root perforation repair.

Methods: A three-dimensional model of a maxillary first premolar was constructed based on clinical cone-beam computed tomography data. Sixteen finite element models were established, including intact teeth, root-filled teeth, perforated teeth with or without repair (unR/R groups), and varying bone defect radii (0 ∼ 3 mm). Root perforation at the middle third and repaired by MTA was simulated. A vertical occlusal force of 300 N was applied via finite element analysis software (Cosmos Simulation) to analyze maximum principal stress (MPS) and displacement. Material parameters were defined as isotropic and linearly elastic based on literatures.

Results: MTA repair of root perforation reduced the average maximum MPS in dentin by 73%. As bone defect radius increased, the unR group exhibited fluctuating increases in maximum MPS, while the R group maintained relatively stable maximum MPS levels. The dentin/enamel maximum MPS ratio in the R group recovered to 0.47. Maximum displacement in both groups positively correlated with bone defect size.

Conclusion: MTA repair of root perforation restored physiological load distribution patterns in maxillary first premolars by reconstructing structural continuity, effectively decoupling bone defects from stress concentration. However, it could not fully counteract the increased displacement caused by periodontal support loss.