摘要
Abstract
Objective·To compare differences in the bone remodeling/tooth movement ratio(B/T ratio)between the skeletal stable structure reference system and the dental long-axis reference system among extraction patients(extracted bilateral first premolars)undergoing maxillary anterior retraction and intrusion with micro-implant anchorages.Methods·A total of 23 samples were retrospectively analyzed.Pretreatment and posttreatment cone-beam computed tomography(CBCT)data,along with pretreatment demographic(age,gender)and cephalometric parameters(ANB angle and FMA angle),were collected from patient records.All subjects underwent standardized orthodontic treatment protocols.Using Dolphin Imaging software,pretreatment and posttreatment CBCT images were superimposed.Labial inclination changes,incisal edge sagittal displacements,root apex sagittal displacements,and intrusion values were measured under skeletal stable structure reference system.For both group G(skeletal stable structure)and group Y(dental long-axis),tooth movement distances,bone remodeling distances,and B/T ratios were measured at three levels:alveolar crest(Level 1),mid-root(Level 2),and root apex(Level 3).Normalized data were compared to evaluate intergroup differences in B/T ratios.Results·Average ANB and FMA angles were 6.00 °±2.08° and 30.24 °±5.95°,respectively,consistent with skeletal Class Ⅱ malocclusion and vertical hyperdivergence tendencies.The maxillary central incisors exhibited sagittal displacement gradients in which incisal edge displacements[right:(6.07±2.58)mm;left:(6.33±2.27)mm]exceeded apical displacements[right:(3.92±2.06)mm;left:(3.90±2.27)mm].Concurrently,intrusion values demonstrated comparable vertical changes bilaterally[right:(2.90±1.51)mm;left:(2.87±1.80)mm],accompanied by labial inclination changes of 4.26°±9.19°(right)and 4.00°±8.84°(left).In group G,tooth movement distance progressively decreased from Level 1 to Level 3,whereas no such gradient was observed in group Y.Both groups demonstrated decreasing bone remodeling distances and B/T ratios from Level 1 to Level 3.After normalization,statistically significant intergroup differences(P＜0.05)were identified across all measurement levels except for the B/T ratio at Level 1 of the left maxillary central incisor.Conclusion·When evaluating alveolar bone remodeling during orthodontic retraction and intrusion of maxillary anterior teeth with micro-implant anchorages,the skeletal stable structure reference system provides more accurate assessments than the dental long-axis reference system,as the latter is susceptible to displacement artifacts inherent to the reference itself.关键词
骨改建/牙移动/锥形束计算机断层扫描Key words
bone remodeling/tooth movement/cone-beam computed tomography分类
医药卫生
