Dental arch changes in postretention in Class II division 1 extraction cases

Abstract

© 2017 CEO Objective The purpose of this study is to evaluate the postretention stability of the dental arches in Class II division 1 patients treated with four bicuspid extractions and the edgewise technique. Materials and methods A digital caliper was used to analyze the dental casts from 29 Class II division 1 malocclusion patients with skeletal type II (14 males, 15 females; ages ranging from 10.2–18.0 years), treated with four bicuspid extractions and the edgewise technique. Intercanine width, intermolar width, arch length, irregularity index, overjet and overbite were evaluated at three times: pretreatment (T1), posttreatment (T2) and postretention (T3) (mean: 4.15 years). Student's t-tests were used to compare the pretreatment–posttreatment, posttreatment–postretention and pretreatment–postretention. Significance was determined at P < 0.05. Results The results of the study are listed as: (1) The upper and lower intercanine widths significantly increased (P < 0.05) between T1–T2 and decreased between T2–T3. However, no significant changes were observed between T1–T3; (2) The upper and lower intermolar widths significantly decreased (P < 0.05) between T1–T2, between T2–T3 and between T1–T3, except for the upper intermolar width between T2–T3 which showed no significant change; (3) The upper and lower arch lengths significantly decreased (P < 0.05) at posttreatment and postretention due to the closure of extraction spaces. Both the upper and lower arch lengths significantly decreased between T1–T2, T2–T3, and T1–T3, except for the upper arch length between T2–T3, which showed no significant change; (4) The irregularity index was significantly improved after treatment. However, there was a slight increase in incisor irregularity at postretention. At postretention, 75.86% of the patients had mild crowding, 20.68% had moderate crowding, 3.48% had severe crowding; (5) The overjet and overbite significantly decreased (P < 0.05) between T1–T2 and increased between T2–T3. Conclusion The changes in the dental arches were small at postretention with a tendency to return towards their original position. The overall stability of Class II division 1 extraction cases is relatively good.