CBCT analysis of incisor movement and alveolar bone changes in class two malocclusion treatment with premolar extraction using clear aligner: a retrospective study.

OBJECTIVES: This retrospective study evaluates alveolar bone remodeling patterns and their association with incisor displacement in adults undergoing clear aligner therapy with premolar extractions for Class II malocclusion correction.

METHODS: Cone-beam computed tomography (CBCT) scans of 38 maxillary and 37 mandibular incisors were analyzed. Displacement vectors for four anatomical landmarks (cusp tip [C], root apex [R], root neck midpoint [M], labial cementoenamel junction [L]) were quantified. Alveolar bone thickness was measured at mid-root and apical levels. Statistical analyses included Spearman correlations and multivariate regression.

RESULTS: Post-treatment maxillary incisors demonstrated labial bone thickening (+0.36±0.44 mm central; +0.15±0.42 mm lateral) with concurrent palatal bone resorption (-0.43±0.64 mm central; -0.22±0.92 mm lateral, P< 0.05). Negative correlations emerged between mid-root thickness of the palatal bone (B2-B2') at R in central incisors (P < 0.05), while lateral incisors showed positive associations between mid-root thickness of labial bone (A2- A2')and C and M displacements (P < 0.05). Mandibular central incisors showed a negative correlation at the mid-root level with points C, M, R, and L (P<0.01), and a multiple regression highlight between point M and (B2-B2') (P<0.05).

CONCLUSIONS: Differential maxillary-mandibular bone responses to clear aligner mechanics highlight the necessity for torque-optimized aligner designs and CBCT-monitored treatment staging to mitigate excessive resorption.