BACKGROUND: Lingual bracket system is the best invisible orthodontic appliance due to its aesthetics and efficiency, but it is difficult to control anterior tooth torque during the distal retraction of the anterior tooth. Thereafter, lots of studies on maxillary anterior teeth have been conducted, but there is less knowledge about the mechanical characteristics of whole mandible dentition distal retaction. OBJECTIVE: To analyze the biomechanical characteristics of the mandibular anterior teeth distal retracted by sliding method in lingual orthodontic treatment. METHODS: A three-dimensional finite element model was constructed using a series of specialized software based on volunteer's CT data and lingual brackets, including the mandible, alveolar bone, periodontal ligament, dentition (removal of the two first premolars), lingual brackets and arch wire with hooks (located between lateral incisor and canine and 11 mm distant from the arch wire plane). Subsequently, 1.5 N lingual forces through the hooks of first molar (2 mm distant from the arch wire plane) and the hooks between the lower lateral incisor and canine were loaded and the biomechanical characteristics of the mandibular anterior teeth movement during the en-masse retraction were analyzed. RESULTS AND CONCLUSION: The finite element model was constructed successfully, and had a higher geometrical similarity and resemblance of clinical situation. The crowns of lower incisors showed the tendency of lingual inclination and extension, and this tendency was more obvious in the lateral incisors. The canines were buccal and mesial inclination and intrusion. The periodontal stress concentration area was corresponded with the tendency of tooth movement. Therefore, the movement tendency of incisors is still lingual inclination when mandibular anterior teeth distal retracted by a longer hook in lingual brackets system, and there is no distal inclination. Overall, lower incisors are easy to exhibit lingual inclination; the long anterior hooks contribute to the movement of canines, but it is not available for the vertical control of incisors during mandibular anterior tooth distal retraction.%背景:舌侧矫治技术是目前最能兼顾美观及高效等优点的隐形矫治技术,但其在前牙较大范围内收的过程中,前牙转矩的控制较难,对此学者们进行了较多力学研究,但多针对上颌牙列,对下前牙整体内收的力学特征的研究相对较少.目的:分析舌侧矫治技术滑动法整体内收下前牙时牙移动的生物力学特征.方法:利用志愿者的CT扫描数据及舌侧托槽等实体数据,通过一系列专用软件的运行,建立包含下颌骨、牙周膜、牙列(拔除左右第1双尖牙)、舌侧托槽、有牵引钩(位于侧切牙与尖牙之间,距离弓丝平面11 mm)的舌侧弓丝等的整体下颌三维有限元模型,利用此模型,在前牙区舌侧牵引钩和第1磨牙舌侧牵引钩间(距离弓丝平面2 mm)加力1.5 N整体内收下颌前牙,初步分析加载条件下前牙位移趋势和牙周膜应力分布特征.结果与结论:建立了舌侧矫治技术整体内收下前牙的整体三维有限元模型,该模型几何相似性强,临床模拟度较高.加力后,切牙牙冠均有舌侧倾斜并伸长移动趋势,侧切牙更明显.尖牙则颊倾并近中倾斜及压低移动趋势.牙周膜的应力分布与牙齿的位移趋势相适应.故舌侧矫治技术前牙区较长牵引钩整体内收下前牙时,切牙仍呈舌倾移动趋势,尖牙无远中倾斜趋势.可见舌侧矫治技术整体内收下前牙时,前牙更易舌倾,长牵引钩有利于尖牙的整体移动,对切牙的垂直向控制不利.
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