不同牵引位点进行骨性支抗上颌前方牵引时骨缝应力分布特征

目的 分析不同牵引位点进行骨性支抗前牵引上颌时骨缝应力分布特征，以指导临床上患者选择合适的前方牵引位点。方法 建立包含种植体的儿童颅面三维有限元模型，根据种植体植入部位设定牵引位点，共分4种工况。工况1:乳侧切牙牙冠远中面远中2 mm与颈缘龈向5 mm交点处牙槽骨；工况2:第1乳磨牙牙冠近中面近中2 mm与颈缘龈向5 mm交点处牙槽骨；工况3:第1磨牙牙冠近中面近中2 mm与颈缘龈向5 mm交点处牙槽骨；工况4:第1磨牙牙冠远中面远中2 mm与颈缘龈向5 mm交点处牙槽骨。分析比较在不同牵引位点前牵引力(与合平面前下成角30°,500 g/侧)作用下各骨缝的应力分布。结果 额颌缝应力在工况2中最大(1 477～28 190 Pa),鼻颌缝应力在工况1中最大(5.296～924 Pa),颧颌缝应力在工况4中最大(394.7～13 130 Pa),颧额缝应力在工况4中最大(495.2～31 690 Pa),颧颞缝应力在工况3中最大(1 148～15 870 Pa),腭中缝应力在工况1中最大(6.479～730 Pa)。结论 当牵引位点置于乳侧切牙远中和第1乳磨牙近中时，对改善鼻根部凹陷明显...

Influences of Stress Distribution on Bone-Anchored Maxillary Protraction at Different Protraction Sites

Objective To evaluate the influence of stress distributions on bone-anchored maxillary protraction at different protraction sites, so as to guide patients to choose an optimal protraction site in clinic. Methods A three-dimensional (3D) finite element model of child head with implant anchorages was establised. Four protraction sites were set according to the position of implant installation. Working condition 1: the alveolar bone at the intersection of distal 2 mm of primary lateral incisor crown distal surface and gingival cervical margin to 5 mm. Working condition 2: the alveolar bone at the intersection of mesial 2 mm of maxillary first primary molar crown mesial surface and gingival cervical margin to 5 mm. Working condition 3: the alveolar bone at the intersection of mesial 2 mm of maxillary first molar crown mesial surface and gingival cervical margin to 5 mm. Working condition 4: the alveolar bone at the intersection of distal 2 mm of maxillary first molar crown distal surface and gingival cervical margin to 5 mm. The finite element models were loaded with 500 g protraction force at each side with 30° forward direction to the occlusal plane. Stress distributions on each suture were analysed. Results The maximum stress of frontomaxillary suture was in working condition 2 (1 477-28 190 Pa). The maximum stress of nasomaxillary suture was in working condition 1 (5.296-924 Pa). The maximum stress of zygomaticomaxillary suture was in working condition 4(394.7-13 130 Pa). The maximum stress of zygomaticofrontalis suture was in working condition 4 (495.2-31 690 Pa). The maximum stress of zygomaticotemporal suture was in working condition 3 (1 148-15 870 Pa). The maximum stress of medianpalatine suture was in working condition I (6.479-730 Pa). Conclusions When the protraction sites are set in distal maxillary primary lateral incisor and mesial maxillary first primary molar, it is of positive significance to improve the concave profile, especially in nose root. When the protraction sites are set in mesial or distal maxillary first molar, it is of positive significance to improve the concave profile, especially in maxillary basal bone of the midface.