正常(牙合)牙尖高度的测量及托槽粘贴高度的再定位

众所周知，矫治完成时同一牙列邻牙间边缘嵴高度应基本一致，每个牙齿的托槽槽沟到其牙齿近远中边缘嵴连线的距离都应基本相等，所以，造成同一牙列中各牙齿托槽粘贴高度不一致的主要原因应该是牙尖高度的不同。因而本研究选取35副正常（牙合）模型为研究对象，以同一牙列中3个后牙的近、远中边缘嵴形成的平面为参考平面，测量各牙齿的牙尖高度值，以此依据来确定托槽的粘贴高度。     

正畸力内收前牙对牙槽骨吸收程度不同后牙的影响

目的 通过有限元法模拟不同程度的后牙牙槽骨吸收状态,分析骨吸收情况下的牙周应力分布和总位移趋势,以便为临床施加合适的矫治力提供指导。方法 在建立正常牙槽骨高度（1号模型）的基础上,通过删减单元格获得后牙牙槽骨高度水平均衡降低2、4、6 mm的2、3、4号模型;在各模型上进行模拟加载,加载力1.47 N,分析在施加矫治力的情况下,各模型后牙组牙的牙周膜初应力及牙齿初始总位移的分布情况。结果 随着牙槽骨高度的降低,后牙组牙总位移增加,牙周膜Von Mises应力逐渐增大,当牙槽骨吸收达4 mm时,应力值和牙齿初始总位移值明显增加。结论 对于伴有牙槽骨丧失的患者,应当避免受力或显著减小受力,避免造成牙周组织不可逆的损伤和牙根、牙槽骨的持续吸收。     

正畸力内收前牙对牙槽骨吸收程度不同后牙的影响

目的 通过有限元法模拟不同程度的后牙牙槽骨吸收状态,分析骨吸收情况下的牙周应力分布和总位移趋势,以便为临床施加合适的矫治力提供指导。方法 在建立正常牙槽骨高度（1号模型）的基础上,通过删减单元格获得后牙牙槽骨高度水平均衡降低2、4、6 mm的2、3、4号模型;在各模型上进行模拟加载,加载力1.47 N,分析在施加矫治力的情况下,各模型后牙组牙的牙周膜初应力及牙齿初始总位移的分布情况。结果 随着牙槽骨高度的降低,后牙组牙总位移增加,牙周膜Von Mises应力逐渐增大,当牙槽骨吸收达4 mm时,应力值和牙齿初始总位移值明显增加。结论 对于伴有牙槽骨丧失的患者,应当避免受力或显著减小受力,避免造成牙周组织不可逆的损伤和牙根、牙槽骨的持续吸收。     

上颌埋伏中切牙向新生牙槽骨内移动的三维有限元分析

目的　分析拔除多生牙后不同施力时机对埋伏牙矫治效果的影响,为临床矫治上颌唇侧阻生中切牙提供一定的理论依据。方法　建立上颌中切牙唇向阻生的三维有限元模型,于牙槽骨不同愈合时期向埋伏牙施以相同的复位力,分析埋伏牙、牙周膜、牙槽骨的初始应力及位移情况。结果　随着牙槽骨的愈合,牙齿、牙周膜的最大应力与位移、愈合期牙槽骨的最大位移逐渐减小,愈合期牙槽骨的最大应力逐渐增大。结论　阻碍埋伏牙正常萌出的多生牙去除后,可以即刻施力移动埋伏牙。但早期移动时牙齿的倾斜趋势比较明显,建议初期加载力值应适度减小,以利于埋伏牙的整体移动。     

正常牙尖高度的测量及托槽粘贴高度的再定位

众所周知,矫治完成时同一牙列邻牙间边缘嵴高度应基本一致[1,2],每个牙齿的托槽槽沟到其牙齿近远中边缘嵴连线的距离都应基本相等,所以,造成同一牙列中各牙齿托槽粘贴高度不一致的主要原因应该是牙尖高度的不同。因而本研究选取35副正常牙合模型为研究对象,以同一牙列中3个后牙     

中国人牙齿临床冠中心高度的研究

直丝弓托槽要粘贴在临床冠中心上，临床上可参考牙齿临床冠中心的平均高度值辅助定位。本文对６７付正常模型进行三维精密测量，得到中国人牙齿临床冠中心的平均高度值，可应用于中国人直丝弓托槽辅助定位。并发现其高度值的规律为：上下牙列从尖牙向后，临床冠中心高度值有逐渐减少的趋势；上颌第二磨牙最小。中国人临床冠中心高度值与白种人相比，具有种族差异。中国人直丝弓托槽不应延用白种人相应数值或者方丝弓托槽高度值辅助定位。     

直丝弓托槽粘贴高度对转矩角影响的研究

直丝弓托槽要粘贴在临床冠中心上,但临床上粘贴高度常存在着偏差,影响到托槽转矩角的发挥。本文通过对６７副正常模型的测量显示：临床冠中心龈向和向０．５ｍｍ处的转矩角的改变,其数值基本相等,而方向相反;从前牙到后牙,转矩角变化值呈增加趋势;转矩变化的幅度为２°～５°;此结果可为直丝弓矫治器临床上相应的转矩调整提供参考。     

上中切牙牙周支持组织高度降低的三维有限元分析

目的:研究牙周支持高度降低状态下施加舌向集中力时,牙周组织的应力变化、分布规律和牙的初始位移。方法:采用螺旋CT扫描、数字影像传输与转录方法,获得中切牙三维形态的原始数据。通过减少牙周支持组织的高度,产生代表6种不同牙周支持高度的三维有限元模型。结果:随着牙槽骨高度的降低,上中切牙牙周膜最大等效应力和主应力逐渐增大。最大拉应力位于舌侧根尖部,最大压应力位于舌侧牙槽嵴顶。牙周膜的应力随牙槽骨高度的降低呈非等比增加。结论:随着牙周支持组织高度的逐渐降低,牙的旋转中心向根尖移动,牙周支持组织对牙的支持能力明显减弱。在正畸治疗中,所应用的力必须成比例减小,以维持正常生理的可耐受的运动而不造成支持组织的进一步损伤。     

重度氟斑牙直接贴面粘接托槽降低托槽脱落率的实验研究

目的通过氟斑牙与正常牙托槽的剪切粘接破坏力和拉伸粘接破坏力的对比性研究,探讨正畸临床重度氟斑牙采用光固化复合树脂直接贴面粘接托槽,增加氟斑牙与托槽粘接强度的方法.方法选择拔除的重度氟斑牙30颗和正常牙10颗,做为实验样本.将正常牙设为对照组.氟斑牙按照氟斑牙釉质表面处理方法的不同分为氟斑牙直接粘接托槽组,氟斑牙表面磨除粘接托槽组,氟斑牙直接贴面粘接托槽组,每组为10颗牙齿,每一牙面粘接方丝弓托槽.采用万能材料试验机分别对四组牙齿进行剪切粘接破坏力、拉伸粘接破坏力的测定.并对每一粘接破坏面发生的部位进行记录分析.结果氟斑牙三个粘接组间的剪切粘接破坏力和拉伸粘接破坏力差异均有显著性(P＜0.01).以氟斑牙直接贴面粘接托槽组的剪切粘接破坏力(329±30.2)和拉伸粘接破坏力(163.1±15.2)最大.正常牙粘接托槽组、氟斑牙表面磨除粘接托槽组粘接破坏面多发生在粘接剂与托槽之间,氟斑牙直接粘接托槽组粘接破坏面多发生在釉质与粘接剂之间.结论氟斑牙直接贴面粘接托槽组的剪切粘接破坏力和拉伸粘接破坏力均高于正常牙粘接托槽组,本研究为正畸临床氟斑牙托槽的粘接提供了一种新的方法.     

正畸牵引在牙列拥挤伴严重牙周病治疗中的应用

目的：本文描述了通过正畸向牵引治疗下前牙拥挤伴严重牙周病患者的方法。方法：通过向牵引计划拔除的严重牙周病患牙从而增加局部硬组织骨量,为后续邻牙排齐提供足够的牙槽骨,改善术后软组织结构和形态。结果：12例患者牙齿排列整齐,间隙关闭,牙齿松动度无增加,龈缘整齐,X片显示排入拔牙间隙的牙齿牙周附着可。结论：通过牵引进入稳定期的牙周病患牙,可以增加局部牙槽骨高度,改善龈缘软组织外形,为后续邻牙排入提供好的牙周条件,达到牙列美观,龈缘整齐,治疗效果稳定的目的。     

正畸治疗中上前牙压入的Typodont研究

目的 :运用Typodont对方丝弓矫治器上应用Vbends弓托槽翼上结扎压低上前牙进行实验研究。 方法 :在Typodont上对Vbends弓托槽翼上结扎 ,托槽槽沟内结扎以及连续摇椅弓三种压低上前牙的方法进行对比研究。结果 :Vbends弓托槽翼上结扎方法在上前牙的压入及支抗磨牙控制方面的效果较好。结论 :Vbends弓托槽翼上结扎是正畸临床可以选用的一种压低上前牙的方法     

微种植体支抗压低上前牙的Typodont实验研究

目的在Typodont模型上,模拟临床应用微种植体支抗压低上前牙的过程,研究不同部位支抗对上前牙压低效果的影响。方法制作上前牙槽骨垂直发育过度的标准Typodont模型42个,随机分为ABC三组,每组14个。A组在中切牙间植入微种植体,B组在中切牙和侧切牙间植入微种植体,C组在侧切牙和尖牙间植入微种植体,应用镍钛螺簧施0．98N（100g）力压低上前牙。应用三维坐标测量仪测量牙齿标记点的三维位置并获得点云数据,Imageware12软件测量牙齿的压低量及唇（颊）倾斜度,并同时拟合牙弓曲线,研究牙弓及[牙合]平面的变化。结果①三组中上前牙均有不同程度的压低（0．9220mm±0．3037mm～5．2354mm±0．9620mm）,中切牙的压低量〉侧切牙〉尖牙,微种植体的位置越靠前,压低效果越明显。②所有牙齿均向前移动,上前牙有不同程度的唇倾,微种植体的位置越靠后,牙齿向前移动越少,唇倾越少。③微种植体的位置越靠后,牙弓及[牙合]平面的变化越小。结论①应用微种植体支抗可以有效地压低上前牙,上磨牙并未伸长。②微种植体的位置越靠后,上前牙的压低量越小,唇倾越少,牙弓变化及[牙合]平面角减少的趋势越小。反之亦然。     

双排沟托槽力学性能的初步实验分析

目的 设计研制双排沟托槽固定矫正装置,并应用模拟(牙合)架进行力学性能测试,分析该矫治系统对正畸牙移动的调控能力。方法 ①设计并制造双排沟托槽及颊管。托槽设置龈端与切端双排槽沟,规格为0.022×0.028英寸(0.56mmm×0.71mm),相距0.8mm。配置相应的双排颊管;②用经典(牙合)架模拟方法进行牙齿反扭转、竖直、整体远中牵引等正畸牙移动形式,与标准方丝弓矫治方法相比较,定量评价双排沟托槽的牙齿移动及调控效率;③应用经典力学原理,结合骀架模拟数据,分析双排沟托槽装置提高正畸牙移动及调控效率的机制。结果(1)成功设计出双排沟矫正装置的三维模拟图形并制造出实际产品;(2)在(牙合)架模拟状况下,双排沟托槽矫正装置对尖牙的反扭转及竖直移动效率均高于对照组(P<0.01);对尖牙远中牵引的整体移动效率高于对照组(P<0.01)。结论 双排弓丝与双排沟托槽翼突底部四点接触所形成的受力平面可能是导致双排沟托槽有效调控正畸牙各种移动的主要机制。     

标记型直丝弓托槽定位器的临床效果评价

目的:评价应用标记型直丝弓托槽定位器后,能否提高托槽粘接的准确性。方法:随机选择35例正畸患者,随机选择其左侧或右侧牙齿为实验组,另侧为对照组,在实验组牙面应用标记型直丝弓托槽定位器粘接直丝弓托槽,在对照组牙面按传统方法完成托槽粘接,粘接完成后常规取模型,在模型上观测实验组与对照组托槽粘接误差的区别。结果:实验组托槽粘接误差的发生率低于对照组,有显著性差异。结论:标记型托槽定位器的应用能明显提高托槽粘接的准确性。     

Patterns of initial tooth displacements associated with various root lengths and alveolar bone heights

The present study was designed to investigate the nature of initial tooth displacements associated with varying root lengths and alveolar bone heights. A three-dimensional model of the upper central incisor was developed for the finite element analysis. Tooth displacements were determined at various levels of the tooth and the apicogingival levels of the center of resistance and centers of rotation were calculated. The results showed that moment-to-force values at the bracket level for translation of a tooth decreased with shorter root length and increased with lower alveolar bone height. In addition, apicogingival levels of the center of resistance shifted more gingivally to the cervix, or the alveolar crest with a shorter root. Alveolar bone loss also shifted the center of resistance toward the alveolar crest, whereas its position was more apical relative to the alveolar bone heights exhibited very slight changes in both cases. The centers of rotation from a single force varied substantially with a short root and alveolar bone loss. However, the relative distances of the centers of rotation from the alveolar crest in comparison with the alveolar bone heights were constant at 0.4 mm, with variations in the root length and alveolar bone height. Because this study showed that root length and alveolar bone height affect the patterns of initial tooth displacements both in the center of resistance and the centers of rotation and also in the amount of displacement, forces applied during orthodontic treatment should take into consideration the anatomic variations in the root length and alveolar bone height so as to produce optimal and desired tooth movement.     

Changes in efficiency of orthodontic tooth movement resulting from differences in bracket materials

The distance of distal movement of the lower canine was measured, using metal tooth with metal bracket and three types of ceramic bracket (polycrystal alumina x 2, zirconia x 1). Sizes of the wires used in this experiment were 0.018" round, 0.016" x 0.022" and 0.17" x 0.022". The bracket slot and the wire surface employed in the experiment were observed by use of stereoscopic microscope and S.E.M. The following results were obtained. 1. The distance of tooth movement with three types of ceramic bracket was significantly less than that with the metal bracket. 2. Rate of decrease in tooth movement with three types of ceramic bracket ranged from 30% to 60% in comparison with the metal bracket. 3. The wire surface was obviously scratched by the ceramic brackets, whereas slight scratch was observed on the wire with the metal bracket. 4. The distance of tooth movement decreased associated with an increase of wire size. 5. The distance retracted from the cuspal position was less than that from the cervical point. It was shown that efficiency of tooth movement was significantly reduced by the use of ceramic brackets in comparison with the metal bracket. This result seems to be caused by the frictional resistance between the wire and ceramic bracket. It is suggested that refinement of ceramic brackets, slot edge and surface in particular, would produce more efficient and desirable tooth movements in clinical orthodontics.     

Determination of the centre of resistance during en masse retraction combined with corticotomy: finite element analysis

Objective: To determine the effect of corticotomy on the change in the centre of resistance of the six maxillary anterior teeth

Materials and methods: Three-dimensional finite element models of the maxillary anterior teeth with and without corticotomy were constructed. Brackets (size 0.022?inch?×?0.028?inch) were placed passively on all anterior teeth that were set at the centre of the labial surface in the mesio-distal dimension and 3?mm from the incisal edge to the bracket slot in the vertical direction. The power arm was set mesial of the canine bracket. For the model with corticotomy, the bone density was decreased from initial value at 5% to 25%. The point of force application was varied in order to locate the centre of resistance. The centre of resistance was located by measurement of the difference of the displacement between the apical and incisal edges. The position of force was varied by moving apically parallel to the occlusal plane to simulate tooth movement.

Results: As the alveolar bone density decreased from initial value to 25%, the location of the centre of resistance moved apically from the bracket slot from 10.8?mm to 11.2?mm, respectively.

Conclusions: The change of alveolar bone density due to corticotomy was associated with the location of the centre of resistance. The location of the centre of resistance moved apically as the alveolar bone density decreased but it was not clinically noticeable.     

Alveolar bone resorption and the center of resistance modification (3-D analysis by means of the finite element method).

The main goal of this research was to study the behavior of initial tooth displacements associated with alveolar bone loss situations when loaded by a force of 1 N. The analysis of displacements was carried out by the finite element method. Six 3-dimensional models of an upper central incisor (designated Geramy 391 to 396) with 1 to 8 mm of alveolar bone loss were formulated and used by the author. Center of rotation and center of resistance were located for the various stages of alveolar bone loss. The results revealed that the moment/force ratio (at the bracket level) required to produce bodily movement increases in association with alveolar bone loss. Bone loss causes center of resistance movement toward the apex, but its relative distance to the alveolar crest decreases at the same time. Greater amounts of displacements of incisal edge and apex were observed with increased alveolar bone loss for a constant applied force. Center of rotation of the tipping movement also shifted toward the cervical line. Among the many differences between orthodontic treatment of an adolescent and an adult patient is the presence of alveolar bone loss in the adult cases. Alveolar bone loss causes center of resistance changes as a result of the alterations in bone support. This necessitates modifications in the applied force system to produce the same movement as in a tooth with a healthy supporting structure.     

Alveolar bone loss induced by the orthodontic tooth movement under hypofunctional conditions in rats

PurposeTo examine the effect of occlusal hypofunctional conditions on orthodontic tooth movement and its relation to the structure and quality of alveolar bone using the rat model.Materials and methodsTwelve-week-old male Sprague-Dawley rats were divided into 4 groups of 8 animals each: normal occlusion (N) group, normal occlusion with tooth movement (M) group, occlusal hypofunction (H) group, and occlusal hypofunction with tooth movement (HM) group. In H and HM groups, the anterior bite plate and metal cap were attached to the maxillary and mandibular incisors using a light-curing composite resin to induce the occlusal hypofunctional condition. In M and HM groups, an orthodontic force was applied in a palatal direction to the buccal surface of the maxillary first molar (M1) using a nickel–titanium alloy wire. Micro-CT imaging and histomorphometric analysis using fluorescent bone labeling of the alveolar bone surrounding the M1s were performed in each group.ResultsTooth movement of M1 in HM group, was rather accelerated with enhanced tipping than in M group. Micro-CT analysis revealed significant decrease in bone volume fraction, bone mineral density and trabecular thickness of the interradicular bone in HM group among the experimental groups. The fluorescent labeling lines in the interradicular bone were decreased in number in H and M groups compared with N group. A few discontinuous irregular dotted lines-like labeling was observed in HM group.ConclusionThe occlusal hypofunctional condition accelerates orthodontic tooth movement of the respective teeth, while it results in severe bone loss in the surrounding alveolar bone.