ObjectiveAlveolar bone height and thickness changes in the maxillary anterior region were assessed before treatment (T1), after treatment (T2), and during the retention phase (T3) in patients with maxillary protrusion treated with clear aligners combined with premolar extraction. The aim was to provide clinical insights for safely retracting anterior teeth with clear aligners.MethodsThis retrospective study included 15 patients (2 males and 13 females) with maxillary protrusion, who underwent bilateral maxillary first premolar extraction and anterior tooth retraction with clear aligners. Cone beam computed tomography images were collected at T1, T2, and T3 (≥18 mon-ths post-treatment) for the measurement of vertical alveolar bone height (labial, palatal, mesial, and distal aspects) and horizontal alveolar bone thickness (labial, palatal, and total). Statistical analysis was performed using SPSS 26.0, and changes across phases and correlations were assessed.ResultsAfter orthodontic treatment, the palatal and mesial alveolar bone height of the maxillary anterior teeth significantly decreased (P<0 .05). concurrently, the labial midroot and apical thickness of the maxillary central incisors showed a significant increase, whereas the palatal cervical alveolar bone of the maxillary lateral incisors and canines exhibited significant thinning (P<0 .05). at t3, the labiopalatal alveolar bone height of the maxillary central incisors significantly increased (palatal height increase: 0.46 mm±0.57 mm;P<0 .05). although the palatal alveolar bone thickness of the maxillary lateral incisors and canines continued to decrease, the differences were not statistically significant (P>0.05). A negative correlation was observed between alveolar bone resorption during treatment and bone regeneration during retention (labial height of maxillary central incisors:r=-0.597,P<0 .05).ConclusionAfter the retraction of maxillary anterior teeth with clear aligners, the alveolar bone height on the mesial and palatal sides of the upper anterior teeth showed considerable reduction. The palatal alveolar bone thickness at the cervical and middle root levels of the upper lateral incisors and canines decreased remarkably. By contrast, the labial alveolar bone thickness at the middle and apical root levels of the upper central incisors significantly increased. At T3-T2, the partial recovery of alveolar bone height and thickness was observed, but pretreatment levels were not reached. Notably, the degree of bone resorption during treatment may influence the remodeling potential at T3.
