Physiological drift of teeth in upper arch after bi-maxillary first premolar extraction

Abstract

Objective To study the distance and pattern of the movement of the maxillary teeth after 6 months driftodontics for dental crowding.Methods 20 dental crowding children,according to the treatment plan,who were required to removal four first premolars,were involved in this study (8 males,12 females,aged 11-14 years old).All of the children did not wear appliance in six months after teeth extraction.X-ray image data before and six months after teeth extraction were collected.The width of extraction space,the anterior irregular index and inclination of the axis of each tooth were recorded before and six months after tooth extraction.The data were analyzed by t-test and Pearson relative analysis.Results The study model showed that bilateral maxillary space of extraction pre-and pro-driftodontics decreased (5.79 ± 4.9) mm (P ＜ 0.01) ; anterior crowding decreased (5.79± 4.12) mm,irregular index was significantly reduced (P＜0.01).Cephalometric film measurement showed that canine crown moved distally (4.87±3.54) mm after the drift (P＜0.01).Canine tooth axis changed from mesial to upright.The crown of maxillary first molar moved mesially (1.18± 0.52) mm (P ＜ 0.01).There were no significant changes in apical position.Conclusions After 6 months of the physiological drift,upright moving of canine relieves anterior teeth crowding.The molar anchorage is saved. Key words: Physiological drift; First premolar; Maxillary