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.

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OBJECTIVETo evaluate the difference of mesiodistal root angulation between panoramic radiograph and panoramic images reconstructed from cone beam computed tomography (CBCT) by different methods.

METHODSCBCT and panoramic radiograph of twenty patients were collected. The InvivoDental 5.0 was separately applied for maxillary or mandibular panoramic image reconstruction. The reconstruction method was combined by two head positions, the Frankfort plane horizontal position (P1) and the occlusal plane horizontal position (P2), and three central planes of focal trough (root apical plane, tooth center plane and crown marginal plane referring to the central incisor). Variation of tooth morphology in reconstructed panoramic images and panoramic radiograph was firstly observed. And then measurement for maxillary or mandibular anterior tooth intersection angle (contiguous angles among 321 123 were named as UA1-UA5; and those among 321 123 were named as LA1-LA5 ) was taken. The difference of intersection angles between reconstructed panoramic images and panoramic radiograph (ΔUA and ΔLA) were calculated. Wilcoxon Rank Sum Test was finally applied to compare the intersection angles' differences between P1 and P2 with the same central plane of focal trough.

RESULTSPanoramic images reconstructed from CBCT by tooth center plane with P1 for maxilla and P2 for mandible appeared to fulfill the clinically diagnostic demand through the observation. Among the 15 couples of comparison of intersection angles' differences between P1 and P2 by choosing the same central plane of focal trough for maxilla, 7 couples of ΔUA revealed a statistically smaller value in P1 while 1 couple of ΔUA showed an adverse result.In mandible with the same comparison method, 10 couples of comparison did not show statistical difference between P1 and P2, while 4 couples of ΔLA revealed a statistically smaller value in P2 and 1 couple ΔLA showed an opposite result.

CONCLUSIONSBy choosing the tooth center plane, the panoramic images reconstructed from CBCT with the Frankfort plane horizontal position in maxilla and the occlusal plane horizontal position in mandible were equally effective. The reconstructed panoramic images can be used as the panoramic radiograph in the assessment of the mesiodistal root angulation.

Cone-Beam Computed Tomography ; Dental Occlusion ; Humans ; Image Processing, Computer-Assisted ; Mandible ; Maxilla ; Radiography, Panoramic ; Tooth ; Tooth Crown ; Tooth Root ; diagnostic imaging