【作者】 李丽华；

【导师】 宋锦璘；

【作者基本信息】 重庆医科大学 ， 口腔临床医学， 2008， 硕士

【摘要】 Ⅱ类错牙合是临床常见的错牙合畸形之一,下颌后缩是II类错牙合畸形的重要特征之一,青少年Ⅱ类错牙合畸形中下颌后缩占46%[1]。下颌后缩畸形严重影响患者的颜貌和功能,根据畸形性质、程度和形成机制,在不同时期应用功能矫治器进行下颌前导是矫治的关键之一。下颌前导功能矫治器依据固位方式不同分为可摘式和固定式。早期功能矫治器大多系可摘式的,矫治下颌后缩往往需双期矫治。近年来,以Forsus为代表的固定式功能矫治器以体积小、弹力持久均匀、矫治力易于控制、安装简便和整体疗程较短等优点,受到了正畸医师的广泛关注,代表了功能矫形治疗发展的趋势。目前,Forsus矫治器的研究主要停留在临床研究阶段,尚未见相关的生物力学研究报道。数值仿真分析是口腔生物力学研究的主要手段之一,是数学科学与计算机技术结合的一种技术,已广泛应用于生物力学的研究。采用数值分析方法对Forsus矫治力系进行仿真分析,利于分析不同前导工况下的力学效应及矫治器的改良,并促进该矫治技术在临床的进一步使用。1本研究紧密结合临床原型,基于成熟的三维有限元快速建模方法,将CT扫描技术、Mimics8.0与Abaqus6.5相结合,利用弹性元件、粘性元件和塑性元件的组合构建骨的粘弹塑性本构关系,建立“Forsus-牙列-上下颌骨-颞下颌关节”三维整体模型。实验中模拟研究Forsus导下颌向前不同工况下牙列、颌骨、颞下颌关节的力学分布状况,重点观察牙齿、颌骨和颞下颌关节的应力场和位移场的变化。在计及粘弹塑性基础上,采用Abaqus6.5运动仿真技术动态分析Forsus反作用力推上颌第一磨牙向远中的力学效应,为Forsus进一步使用和改良提供力学理论依据。基于各向同性、非线性、具有粘弹塑性的“Forsus-牙列-上下颌骨-颞下颌关节”模型,在不同下颌前导的工况下,Forsus导下颌向前时应力衰减不明显,没有明显应力松弛区域,即时效分析颌骨改建是个较缓慢的过程。尤其是加载角度偏离基准线越远,颏部前伸位移越明显;下颌骨逆时针旋转比顺时针旋转前伸位移更明显;因此Forsus加载角度推荐范围在0°与25°之间。当转动中心位于下切牙切缘,下颌骨向前的旋转方式有利于II类错牙合畸形的治疗。生长型不利的患者,可通过调整Forsus加载角度,增加下颌有利的自动旋转方向,利于侧貌的改善。Forsus前导下颌后位移场仿真分析发现髁突生长改建范围在1.0到3.0mm之间,符合生理范围内的改建。当矫形力矢量通过磨牙冠颊侧表面的中心时,辅以Mt/F = 9的反倾斜力偶和Mr/F = 5的反旋转力偶,将获得第一磨牙的远中平移效果。本研究建立了具有一定粘弹塑性生物力学特性的“Forsus-牙列-上下颌骨-颞下颌关节”各向同性、非线性的三维整体模型,几何相似性和力学相似性较高,可拆分并模块化应用,为深入探讨前导下颌的Forsus生物力学效应提供了研究平台。此外,通过模拟研究不同前导工况下的Forsus矫治力系分布效应,为其进一步的临床应用和改良提供了有利的借鉴。更多还原

【Abstract】 ClassⅡmalocclusion is patho-occlusion in clinic. One of its significance characters is the mandibular retraction. Among adolescents with mandibular retraction, 46 percent of them suffer from ClassⅡmalocclusion . The abnormity influences the patients’countenances and functions severely. According to the abnormity’s nature, extent and formation in different periods, it’s important for patients to be treated by submaxilla anterior guidance .Owing to the different retention modes, submaxilla anterior guidance activator can be classified as removable appliance and fixed appliance. Most of the appliances which used in the earlier period were removable, and the treatment of mandibular retraction needed two-phases treatment. In recent years, a great number of orthodontic doctors pay close attention to fixed appliance which prescented by Forsus ,for such appliance is small in size, has more durable and homogeneous elastic foce and easy to control, too. What’s more, the installation is easier and the course of treatment is shorter in general. In a word, fixed appliance suggests the new developmental trend of the orthopaedic treatment appliance . At present, the study of Forsus appliance steps into clinical research phase. None report about vitodynamics study in mandibular anerior guidance is found. Numerical simulation analysis is one important means in oral biomechanical study, it is a technique combines Mathematical Sciences and Computer Technology and it has been widely used in vitodynamical study. On the basis of considering visvoelasto, by using the simulated analysis of the Forsus orthopedic force system, the different mechanical effects can be analysed under different anterior guidance operating conditions, and the analysis improves the clinical use of the appliance as well .In this study, Forsus-Dent-uper and lower jaw-TMJ integral 3D model with the character of isotropy and non-linear was builded. To some extent the model also is built with the character of visvoelasto.The study shows that there is no obvious stress attenuation, or distinct stress relaxation region,that is, the rebuilding process of jaw bones is slow. The larger the angle between the datum line and loading point is the more obvious mental region’s protrusive bias would be. Those who with mandible anticlockwise rotation have more obvious protrusive bias compares with mandible clockwise rotation ones. When Forsus is used, the range of loading angle is from0 to25 degree would be better. In cases with rotation center lies in the Incisal border of lower incisors, a antrorse rotation of the lower jaw would do good to the therapy of type II patho-occlusion. For patients with unfavorable vegetative form ,by adjusting the loading angle of Forsus applicaton, the lower mandible’s expedient automatic rotation orientation would be increased . All the above does good to improve the latero-countenance. The condylar‘s remodeling compass is in the extent of 1.0 to 3mm. Though the remodeling tendency of condylar is significant, this changement is finite. When the orthopedic force-vector through the center of abutment tooth crown’s buccal surface, adding a anti-incline couple of Mt/F = 9 and a anti-rotation couple of Mr/F = 5 would won the molar’s translation.A model of Forsus-Dent-uperand lower jaw-TMJ with some visvelasto-plastic characters is built in this study and it is isotopic, non-linear, three diamensional and integral. It has high geometric and mechanics similarities and could be splited and used in the form of modules. All the above contributes to a research platform for further study of the vitodynamics effect of Forsus in mandible anterior guidance .At the same time, the study offers favourable reference for the clinical application and improvement of Forsus by using simulated analysis on the disposition of the orthopedic forcess system under different anterior guidance operating condition.更多还原