Morphological analysis of roots and alveolar bone changes after upper anterior retraction with maximum anchorage based on cone-beam computed tomography / 北京大学学报(医学版)

ABSTRACT

Objective:To investigate the remodeling of alveolar bone and the changes of roots after an-terior retraction with maximum anchorage by analyzing CBCT data from adult cases.Methods:The sam-ple comprised 48 incisors and 24 canines from 12 patients (18 to 40 years of age)with problems of ma-xillary protrusion or upper arch protrusion.CBCT scans were exposed before and after treatment,and la-teral cephalometric images as well as multiple planar reconstruction images were reconstructed.Tracing superimpositions of sagittal sections and three-dimensional reconstructions were done for qualitative analy-sis.For all maxillary anterior teeth,changes of root length,alveolar bone height and labial-palatal thick-nesses at different levels were evaluated.The average of measurements taken by the same tester in three times was processed by SPSS 17.0 statistical package.Results:In 6 of the 12 cases,alveolar thickness became thinner on labial side [apical area(-0.64 ±1.18)mm]while thicker on palatal side [apical area(0.93 ±2.0)mm]and the root length decreased[(-0.95 ±0.79)mm].In the other 6 cases, the incisors’alveolar bone became thicker on labial side [apical area(2.12 ±1.46)mm]while thin-ner on palatal side [apical area(-2.88 ±0.58)mm]and the loss of root length was obvious[(-2.12 ± 1.43)mm].In all the 12 cases,the canines’alveolar bone became thinner on labial side especially on the apical level [(-0.27 ±1.86)mm]while greatly thicker on palatal side [apical area(6.40 ± 6.00)mm]and the root resorption was slight [(-1.12 ±1.19)mm].For all the anterior teeth,the height of alveolar bone reduced around them after retraction.Conclusion:When the root apical moved more palatally,more root resorption would occur and the alveolar bone would get thicker on labial side but thinner on palatal side and thinner as a whole after anterior retraction with maximum anchorage.In the vertical direction,the height of the alveolar bone generally decreased on all sides and decreased the most on the palatal side.