Corticotomy Depth as a Modulator of Orthodontic Tooth Movement and PDL Stress-A Finite Element Study

Introduction: The aim of this study was to evaluate the effect of corticotomy incision depth on tooth movement and stress distribution in the periodontal ligament (PDL) during orthodontic expansion using finite element analysis (FEA). The demand for accelerated and biologically safe orthodontic techniques has highlighted the importance of understanding biomechanical responses to surgical adjuncts like corticotomy. Objective: The aim of this study is to assess the effect of corticotomy depth on tooth movement and periodontal ligament stress distribution during orthodontic treatment using finite element analysis. Materials and methods: A 3D FEM model was developed based on CBCT and intraoral scans to replicate anatomical structures and simulate clinical orthodontic scenarios. Four conditions were analyzed: no corticotomy and corticotomy incisions of 1 mm, 2 mm, and 3 mm depths, applied between roots and above the apex region. Different cortical bone densities were tested using Young's modulus values (12,500 MPa-27,500 MPa). Stress and displacement values were measured in both the crown and root regions. Results: The 3 mm corticotomy, penetrating through the cortical plate into the cancellous bone, significantly increased crown displacement (up to 26% in low-density bone) and altered root tipping patterns, reducing root movement relative to the crown. Shallower incisions (1-2 mm) had minimal effects. Despite increased movement, stress concentration in the cervical PDL region remained high across all scenarios, particularly in the premolar area, exceeding the 4.7 kPa threshold associated with tissue ischemia. Conclusions: Corticotomy depth is a critical factor for optimizing orthodontic tooth movement. Penetration into cancellous bone (3 mm) appears necessary to induce both: not only the Regional Acceleratory Phenomenon (RAP) but also to enhance displacement. However, this approach does not significantly reduce cervical PDL stress and offers limited periodontal protection. Individual planning based on bone density, morphology, and anatomical limitations is essential for balancing treatment efficiency and periodontal safety.