Anatomical Limits of Mandibular Molar Distalization: A Cone-Beam Computed Tomography (CBCT) Assessment of Retromolar Bone in a Chilean Sample

Abstract

Objective: To perform a three-dimensional analysis of the available bone space and anatomical limits for mandibular molar distalization in a Chilean population using Cone-Beam Computed Tomography (CBCT) and to compare bone values according to skeletal class, facial biotype and molar angulation. Methods: A retrospective study was conducted using 117 CBCT scans of patients (16-60 years). Linear measurements were taken from the distal root of the mandibular second molar to the lingual cortical bone at different levels (2, 4, 6, 8 mm apical to the CEJ and apex). Buccolingual bone thickness and root contact with cortical plates were also assessed. Statistical analyses included one-way ANOVA with Bonferroni post-hoc correction, Student’s t-test and chi-square tests (p < 0.05). Results: Retromolar bone availability significantly decreased as measurements moved apically (p < 0.05). Skeletal Class III and hypodivergent biotypes exhibited significantly greater bone availability and buccolingual thickness compared to other groups (p < 0.05). Additionally, greater molar mesioangulation was significantly associated with a reduced distance to the lingual cortical bone. Root contact with the lingual cortical plate was most frequent at the apical level, particularly in Class II patients. Conclusion: Bone availability for mandibular molar distalization is significantly influenced by sagittal skeletal patterns and facial biotypes, with Class III and hypodivergent individuals exhibiting the most favorable conditions. Increased molar mesioangulation acts as an anatomical constraint. CBCT is essential for individualized planning to establish safe limits for distal movement.