Morphological changes of the anterior alveolar bone due to retraction of anterior teeth: a retrospective study

Abstract

Background: The morphology of the anterior alveolar bone may change after the retraction of incisors in premolar extraction cases in orthodontics. Methods: Pre- (T0) and post-treatment (T1) lateral cephalograms of 477 subjects in the maxilla and 226 subjects in the mandible who underwent the orthodontic treatment with extraction of 2 premolars in upper or lower arches were included. Alveolar bone width and height in both the maxillary and mandible incisor area were measured at T0 and T1 respectively. By superimposing the T0 and T1 cephalometric tracings, changes of points A and B, and the movement of the incisors were also measured. Results: The alveolar bone width (ABW) showed a significant decrease in both maxilla and mandible (P<0.001) except the labial side of the mandible, which exhibited slight increase, though statistically insignificant (P>0.05). The alveolar bone height (ABH) showed a significant increase in the labial side of maxilla and a significant decrease in the lingual side of maxilla and mandible. A strong positive correlation was observed between incisor movement and position changes of points A and B both in the horizontal and vertical direction. Conclusions: Anterior alveolar bone width and height generally decreased after orthodontic treatment. Incisor retraction led to a significant position changes of points A and B.