Division of Orthodontics, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
Am J Orthod Dentofacial Orthop. 2010 May;137(5):648-57. doi: 10.1016/j.ajodo.2008.06.036.
The strategic design of an appliance for correcting a bialveolar protrusion by using orthodontic mini-implant anchorage and sliding mechanics must take into account the position and height of the mini-implant, the height of the anterior retraction hook and compensating curve, and midline vertical traction. In this study, we used finite element analysis to examine effective en-masse retraction with orthodontic mini-implant anchorage and sought to identify a better combination of the above factors.
Base models were constructed from a dental study model. Models with labially and lingually inclined incisors were also constructed. The center of resistance for the 6 anterior teeth in the base model was 9 mm superiorly and 13.5 mm posteriorly from the midpoint of the labial splinting wire. The working archwires were assumed to be 0.019 x 0.025-in or 0.016 x 0.022-in stainless steel. The amount of tooth displacement after finite element analysis was magnified 400 times and compared with central and lateral incisor and canine axis graphs.
The tooth displacement tendencies were similar in all 3 models. The height of the anterior retraction hook and the placement of the compensating curve had limited effects on the labial crown torque of the central incisors for en-masse retraction. The 0.016 x 0.022-in stainless steel archwire showed more tipping of teeth compared with the 0.019 x 0.025-in archwire. For high mini-implant traction and 8-mm anterior retraction hook condition, the retraction force vector was applied above the center of resistance for the 6 anterior teeth, but no bodily retraction of the 6 anterior teeth occurred. For high mini-implant traction, 2-mm anterior retraction hook, and 100-g midline vertical traction condition, the 6 anterior teeth were intruded and tipped slightly labially.
通过正畸迷你种植体支抗和滑动力学来矫正双颌前突的器具的战略设计必须考虑迷你种植体的位置和高度、前牵引钩和补偿曲的高度以及中线垂直牵引。本研究通过有限元分析研究了正畸迷你种植体支抗的有效整体内收，并试图确定上述因素的更好组合。
从牙模构建基础模型，还构建了唇倾和舌倾切牙的模型。基础模型中 6 个前牙的阻力中心位于唇夹板丝中点上方 9mm 和后方 13.5mm 处。工作弓丝假设为 0.019 x 0.025-in 或 0.016 x 0.022-in 不锈钢。有限元分析后的牙齿位移量被放大 400 倍，并与中切牙和尖牙轴的图形进行比较。
3 种模型的牙齿位移趋势相似。前牵引钩的高度和补偿曲的放置对整体内收中切牙的唇冠转矩影响有限。0.016 x 0.022-in 不锈钢弓丝比 0.019 x 0.025-in 弓丝显示出更多的牙齿倾斜。对于高迷你种植体牵引力和 8mm 前牵引钩条件，内收力向量施加在前牙 6 个阻力中心上方，但前牙 6 个牙体没有整体内收。对于高迷你种植体牵引力、2mm 前牵引钩和 100g 中线垂直牵引力条件，6 个前牙轻微向唇侧倾斜。
