Study of tooth drifts after orthodontic extractions in cases of interruption

Objective To compare the tooth drift differences between different types of patients after orthodontic extraction for 1.5 months (45 days) without return to the clinic on time for some reasons. Methods This study has been reviewed and approved by the Ethics Committee, and informed consent has been obtained from patients. A total of 84 patients had bilateral premolars extracted but were not bonded the bracket for some reasons. The upper and lower jaw dental models were cast, scanned, and reconstructed in 3D. Patients were divided into 12 groups based on extraction positions (first premolar or second premolar), jaw types (maxilla or mandible) and vertical facial types (average angle, high angle, or low angle). Multivariate analysis of variance was used to analyze the changes in the following five indicators in different types of patients who were interrupted for 1.5 months after extraction: anterior tooth crowding, width between canines, width between first molars, tooth extraction space, and overbite of anterior teeth. Results The tooth extraction position, jaw type and vertical facial type had an effect on the reduction in tooth extraction space and anterior tooth crowding before and after the sudden emergent state (1.5 months after tooth extraction) (P<0.001), and the tooth extraction position and vertical facial type had an effect on the increase in anterior tooth overbite (P<0.001). The drift of bilateral adjacent teeth was greater in patients with first premolars extracted than in those with second premolars extracted (P<0.001), and the drift of bilateral adjacent teeth in the maxilla was larger than that of the mandible (P<0.001). The drift of bilateral adjacent teeth in patients with high angles was more obvious than that of patients with average angles and low angles (P