The character of using miniscrew anchorage in the apical root resorption of maxillary incisors

• Main Authors: CHANG MIN HSIN, 張民欣
• Other Authors: 陳昱瑞
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/55796572048441486940

碩士 === 長庚大學 === 顱顏口腔醫學研究所 === 95 === Abstract Purposes and null hypotheses: The purposes of this study were to study the character of using miniscrew anchorage in the apical root resorption of maxillary incisors, and to explore the possible factors predisposing to the apical root resorption in cases miniscrew anchorage is used for the en masse maxillary anterior retraction-and-intrusion. The null hypotheses were first the apical root resorption of en masse maxillary anterior retraction-and-intrusion with miniscrew anchorage has no difference from that without miniscrew anchorage, and second the dentofacial deformity, direction and extent of tooth movement, and treatment duration are not predisposing factors to the apical root resorption of maxillary incisors when miniscrew anchorage is used for the en masse maxillary anterior retraction-and-intrusion. Material and methods: Sixty-six adult patients with maxillary protrusion were included in this study. In which, 30 patients were treated with miniscrew anchorage and extraction of maxillary first premolars (Group-I), another 16 patients were treated with miniscrew anchorage but without any teeth extraction except third molars in some cases (Group-II), and the other 20 patients were treated with extraction of maxillary first premolars (Group-III). For each patient, periapical films of the maxillary incisors and lateral cephalometric radiographs were taken before (T1) and after treatment (T2). The radiographs were scanned into computer and calibrated and measured in 1:1 ratio under the Image J measurement program for (1) the apical root resorption of the maxillary central and lateral incisors between T1 to T2, (2) the amount of en masse maxillary anterior retraction-and-intrusion between T1 to T2, (3) the T1 upper incisor angle, SNA, SNB, and ANB angle. The inter-group differences were analyzed by ANOVA and independent t-test, and the correlations were analyzed by Pearson correlation analysis. Results: The apical root resorption of the three groups ranged from 12.5% to 20.5% or 1.9 mm to 2.7 mm of the original root length. The Group-I had significantly the most severity of intermaxillary discrepancy, greatest amount of anterior retraction at the incisor tip and root apex, and longest duration of treatment. The apical root resorption of the maxillary lateral incisors in Group-I was significantly greater than those of Group-II and –III. However, due to the varied values of standard deviation, the apical root resorption of the maxillary central incisors was not significantly different among groups. The first hypothesis was rejected due to greater apical root resorption of lateral incisors in Group-I. The apical root resorption of the maxillary central or lateral incisors in the patients who had miniscrews (Group-I combined with Group-II) was significantly correlated to the duration of treatment, amount of anterior retraction, pre-treatment severity of upper incisor proclination, mandibular retrognathism, and intermaxillary discrepancy and the second null hypothesis was rejected. Conclusion: Using miniscrew anchorage for the en masse maxillary retraction-and-intrusion could be a contributing character to the more apical root resorption, especially to the maxillary lateral incisors and in individual who is vulnerable to apical root resorption, and who has severer intermaxillary discrepancy and needs large amount of anterior retraction and longer duration of treatment. Key words: apical root resorption, miniscrew