| Objective:The purpose of this study was to investigate the maxillary anterior alveolar density changes after retraction of maxillary anterior teeth based on CT data retrospectively.Methods:Thirty patients (16females and14males; aged from19to27years, mean age:23.7years; SD:3.4years) with bimaxillary prognathism were collected and all received fixed appliance with biomaxillary1st premolars extracted. Pre-and post-treatment CT scans were performed to measure the alveolar bone densities around the maxilla central incisors and lateral incisors. Around each root six sites were chosen to determine whether the bone density varied. In addition, the retracted distances of upper incisors during the treatment were measured.All measurements were repeated after4weeks by the same investigator, and the mean of the two measurements was chosen in the statistical analysis. Paired-sample t test was chosen to test the intragroup differences of the measurements and whether there was a significant difference in the alveolar bone density before and after orthodontic treatment. The bone density changes in different teeth were analyzed using the One-Way ANOVA. Statistical significance was determined at α=0.05. Results:1. The results of the paired-test indicated high reliability between the two assessments with a mean of0.94(0.89-0.98).2. The measurements of the CT scans showed that the amount of upper incisor retraction at edge and apex were3.75±1.03mm and2.67±0.90mm respectively.3. The labial bone density was reduced after treatment (P＜0.01). The mean bone density changes have no significant statistical difference between the C1, C2, and C3levels of the teeth in labial.4. The palatal bone density was reduced at level L1(P＜0.01), but it was increased at level L2and L3(P＜0.01).Conclusions:The anterior alveolar bone density in buccal and crest level of palate were reduced after orthodontic retraction in bimaxillary prognathism patients while middle and apical parts of the palate bone seemed increased. |
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