无托槽隐形矫治器设计平面导板对上牙列牙齿移动的影响

目的 探讨无托槽隐形矫治器设计平面导板,对上中切牙压低效率的影响及支抗前磨牙、磨牙的变化,以期对无托槽隐形矫治器设计平面导板矫治深覆(牙合)提供参考.方法 分别选取无托槽隐形矫治器设计平面导板和无平面导板矫治深覆(牙合)的病例各6例,两组均设计上中切牙不少于0.7mm的压低,通过前牙压低矫正深覆(牙合).前磨牙及磨牙作为支抗牙不设计移动.以腭穹窿为参照,重叠设计压低前后的数字化模型,比较两组上颌中切牙压低效率的差异,以及两组支抗前磨牙和磨牙的差异.结果 平面导板组上中切牙压低效率为33％,无平面导板组上中切牙压低效率为8％,二者的差异无统计学意义(P＞0.05);平面导板组第一前磨牙、第二前磨牙、第一磨牙和第二磨牙分别伸长0.3、0.1、0.2和0.1mm;无平面导板组第一前磨牙、第二前磨牙、第一磨牙和第二磨牙分别压低0.0、0.2、0.1和0.1mm,两组的差异均有统计学意义(P＜0.05);平面导板组和无平面导板组未设计移动的第一磨牙分别颊倾0.0mm和0.3mm,二者的差异有统计学意义(P＜0.05).结论 无托槽隐形矫治器设计平面导板对上颌中切牙的压低无明显影响,但能有效伸长支抗前磨牙及磨牙,克服无托槽隐形矫治器"(牙合)垫效应"造成的后牙压低,并维持磨牙水平向的位置,对深覆(牙合)的矫正发挥一定作用.     

方丝弓矫治技术中人字型唇弓的临床效果评价

目的:观察人字型唇弓在方丝弓矫治技术中的临床效果。方法:将人字型唇弓应用于5 8例前牙前突、拥挤及深覆牙合患者,分析人字型唇弓的适应症,矫治器的设计及应用,并对矫治前后X线头影测量结果进行统计学分析。结果:上切牙被压低1.43mm ,下切牙被压低2 .5 9mm ,上磨牙有1.0 7mm的伸长,下磨牙有1.41mm的伸长。前磨牙前倾、尖牙后倾的趋势得到纠正,前后牙牙轴得到有效的控制,矫治后可获得良好的牙合关系。结论:人字型唇弓能有效地纠正和预防前磨牙前倾、尖牙后倾并可有效地打开咬合。     

不同前牙唇倾度及内收压低步距下隐形矫治器作用的比较：三维有限元研究

目的:应用有限元分析法探究使用隐形矫治器治疗不同前牙唇倾度以及不同内收压低移动步距下,以分步法内收前牙的牙齿移动特点。方法:建立使用隐形矫治器分步法内收上颌前牙的有限元模型,依据中切牙及侧切牙的唇倾度分为工况1:U1-SN=105°、工况2:U1-SN=115°、工况3:U1-SN=125°,牙齿移动总步距为0.2 mm,包括沿牙合平面的内收以及沿牙体长轴方向的压低,每组工况以内收量a:0.18 mm、b:0.14 mm、c:0.10 mm进行分组,分析上述不同情况下的牙齿移动特点。结果:在不同前牙唇倾度以及内收模式下,中切牙、侧切牙均表现为牙冠向舌侧、牙根向唇侧的倾斜移动,第二前磨牙至第二磨牙表现为牙冠向近中的倾斜移动。内收步距越大,前牙冠舌向位移量越大,前牙转矩改变量越大,第二前磨牙至第二磨牙牙冠近中移动量越大。结论:无托槽隐形矫治器在内收前牙时引起前牙的舌倾及伸长、后牙的近中倾斜,其移动量与内收步距呈正比,预设计的前牙绝对压低量无法抵消由牙齿内收引起的相对伸长量。     

拔牙病例隐形矫治器设计的有限元分析

目的 分析隐形矫治器关闭拔牙间隙的力学特征。方法 选取拔除4颗第一前磨牙病例,设计4种隐形矫治方案,包括前牙整体内收、前牙散开内收、后牙近移、后牙散开,关闭第一前磨牙拔牙间隙,分别对其进行有限元分析。结果 前牙内收方式-前牙无间隙时,内收力更均匀作用于前牙,使其整体受到较大的力,后牙需要提供更大的支抗;前牙有间隙时,内收力首先作用于中切牙,且侧切牙和尖牙的内收力略小于中切牙,后牙需提供的支抗也更小。后牙支抗方式-后牙散开且设计近中移动,有助于保护第二前磨牙的支抗,但第一磨牙、第二磨牙可能受到更大的近移力;后牙散开且无移动设计,第二前磨牙承担更多前牙内收的支抗力,可能有更大的近倾风险;后牙不散开且无设计移动,后牙的支抗力分布更加均匀。结论 前牙内收方式选择应基于不同内收方式作用力的差异,还应考虑个体差异和临床实际;后牙移动方式选择需考虑支抗分布,避免后牙近中倾斜导致开;单步设计更小的矫治量能更好地进行轴向控制。     

应用微钛钉支抗矫治上颌前牙严重拥挤

目的研究应用微钛钉支抗治疗前牙严重拥挤畸形牙齿的治疗变化,介绍该治疗方法的临床要点。材料方法本研究包括8名正畸患者,年龄范围14.5—40.5岁,平均年龄25,7±7.7岁。8名患者的上牙列前牙区牙齿拥挤在Ⅱ度以上,拥挤平均在9.2毫米。粘结矫治器之前在上颌双侧第一磨牙和第二前磨牙之间或双侧第一、第二磨牙间的颊侧分别植入微钛钉种植体。治疗早期应用自攻型微钛钉进行尖牙向远中结扎,并在更换至稳定弓丝后利用微钛钉分期移动尖牙和侧切牙,牵引力值100克力。前牙排齐治疗前后拍摄头颅侧位片,并测量切牙和磨牙的治疗变化。结果 8名应用微钛钉支抗治疗上前牙拥挤组,牙列排齐后中切牙和第一磨牙在前后向和垂直向均未发生显著性移动。结论微钛钉支抗能够有效治疗严重牙列拥挤,可以避免前牙的往复运动,并达到磨牙强支抗的效果。     

无托槽隐形矫治拔牙病例尖牙牙冠远移效率及支抗牙三维位移分析

目的 研究无托槽隐形矫治在拔牙病例中远移尖牙的移动效率和未设计位移支抗牙的实际三维位移.方法 收集无托槽隐形矫治第一前磨牙拔除的成人安氏Ⅰ类、分步法内收前牙患者17例,纳入研究牙齿共计170颗.通过三维扫描将患者治疗前模型和阶段研究模型数字化,利用数字化模型三维重叠技术收集中切牙、尖牙、前磨牙和磨牙的实际位移数据,计算尖牙的远中移动效率及未设计位移支抗牙的实际位移.结果 尖牙平均远移效率为87.78％±9.3％.后牙备抗组尖牙平均远移效率为89.27％±10.2％,后牙非备抗组尖牙平均远移效率为86.27％±6.6％,结果无统计学差异(P=0.438),尖牙设计远中移动1～2mm的移动效率为88.21％±15％,2～3mm的移动效率为87.10％±4.4％,结果无统计学差异(P=0.762).尖牙在矢状向设计位移量为-1.61±0.87mm,实际位移量为-1.47±0.77 mm,差异意义有统计学(P＜0.05),垂直向设计位移量为-0.07±0.35 mm,实际移动量为0.26±0.48 mm,差异意义有统计学(P＜0.05).后牙备抗组第一磨牙垂直向平均位移量-0.10±0.24 mm,后牙非备抗组第一磨牙垂直向平均位移量0.15±0.33 mm,差异意义有统计学(P=0.037).后牙备抗组第二磨牙垂直向位移量-0.08±0.30 mm,后牙非备抗组第二磨牙垂直向位移量0.18±0.32mm,差异意义有统计学(P=0.023);在后牙备抗组和非备抗组中,磨牙的矢状向和颊舌向位移无统计学差异.结论 后牙备抗对尖牙远移效率无显著影响,尖牙远中移动效率较高,但易发生伸长移动;未设计位移的支抗牙在尖牙远移阶段发生了三维位移变化.     

90例汉族年轻成人正常牙形态测量分析

目的: 对上海某高校90例汉族年轻成人正常牙形态进行三维测量,为开发适合中国人牙颌面特征的直丝弓矫治器提供数据参考。方法: 从上海某高校9000名大一新生中筛选出90名18~24岁正常汉族年轻成人,收集全口硅橡胶牙列印模,进行三维扫描,获得数字化牙列模型,用Smartee Ortho（A）三维测量软件测量,获得牙冠轴倾度、转矩角、唇（颊）侧冠凸距指标。采用SPSS 17.0软件包进行统计分析,得出测量结果均值。结果: 测量获得年轻成人正常牙冠轴倾度、转矩角、唇（颊）侧冠凸距均值。关于牙冠轴倾度,除上颌第二磨牙外,其余牙的牙冠均向近中倾斜,上、下前牙轴倾度普遍小于欧美人。关于牙冠转矩,上、下前牙转矩均大于欧美人,尤其是上、下尖牙更为唇倾;上、下后牙转矩小于欧美人,更舌向倾斜。关于牙冠凸距,上中、侧切牙间冠凸距差值小于欧美人,下颌尖牙与侧切牙、下颌第一与第二前磨牙间牙冠凸距大于欧美人。结论: 中国人正常牙冠轴倾度、转矩角、唇（颊）侧冠凸距指标与欧美人存在差异,有必要开发符合中国人牙颌面特征的直丝弓矫治器。     

头帽肌激动器和普通功能矫治器矫治安氏Ⅱ类1分类错[牙合]上下牙列变化的初步探讨

目的分析头帽肌激动器和普通功能矫治器治疗安氏Ⅱ类1分类错[牙合]患者上下牙列变化,从而进一步探讨功能矫治器治疗Ⅱ类错的作用机理,为临床应用提供理论依据。方法选取Van Beek矫治器治疗安氏Ⅱ类1分类错患者22例（简称VB治疗组）,Twinblock矫治器治疗患者23例（简称TB治疗组）。分别选取性别和骨型对应Van Beek治疗前后患者的未治疗安氏Ⅱ类1分类错[牙合]患者各88例,Twinblock治疗前后对照组患者各92例作为对照组,治疗组和对照组患者分别在治疗前后拍头颅侧位片。结果VB组治疗后,上切牙压低,上切牙突度减少,上切牙唇倾度无改变,上第一磨牙推向后,下前牙唇倾度无变化,下第一磨牙伸长。TB治疗组,上切牙伸长,突度减少,上前牙明显舌倾,上第一磨牙推向后,下前牙唇倾,下第一磨牙伸长。结论Van Beek矫治器能压低上前牙,对上切牙转矩有效控制,能控制下前牙唇倾度。普通功能矫治器治疗安氏Ⅱ类1分类错[牙合]使上前牙舌倾,下前牙唇倾。两类矫治器均能使上牙弓远中移动,但Van Beek矫治器作用更大,且均能使下第一磨牙伸长。     

种植钉植入高度对隐形矫治远移下磨牙时应力分布的影响

目的 探究种植钉不同植入高度对隐形矫治配合颌内牵引远移下磨牙时所产生的生物力分布的影响,寻找有利于保护下前牙支抗的种植钉植入位置,为临床治疗方案的设计提供参考。方法 应用Mimics、Geomagic Studio 2017、SolidWorks2016、Ansys workbench建立有限元分析模型并对六种工况进行力学分析。工况一：无种植钉（对照组）;工况二至工况五：种植钉植入于下颌第一磨牙和第二磨牙之间的颊侧骨皮质,距离牙槽嵴顶分别为10 mm、7 mm、4 mm、1 mm;工况六：种植钉植入于下颌升支前缘颊舌向居中,高于平面5 mm的位置。结果 矢状向,种植支抗使所有牙齿均产生远中向位移;相较于对照组,种植钉组前磨牙远中位移量超过第二磨牙。垂直向,对照组（无种植钉）为类似后倾弯对下颌牙列产生的作用;种植钉组侧切牙、尖牙压低,中切牙、第一前磨牙伸长。冠状向,对照组（无种植钉）第二前磨牙、第一磨牙为舌向位移,种植钉组仅前磨牙及第一磨牙出现了舌向位移;所有牙齿中,尖牙的位移量受种植钉植入高度变化影响最大。结论种植钉植入位置越高,保护前牙支抗的效果越强。方案设计时应根据种植钉植入高度,...     

无托槽隐形矫治器远移上颌磨牙的疗效评价

目的:评价无托槽隐形矫治器远中移动上颌磨牙的疗效.方法:选取安氏Ⅱ类错(牙合)患者15例,平均年龄为25.3岁.应用无托槽隐形矫治器远中移动上颌磨牙,通过重叠磨牙远移前后的三维数字化模型,并进行三维测量分析评价其远中移动磨牙的疗效.结果:双侧第一磨牙均平均向远中移动2.58 mm,左右侧第二磨牙分别平均向远中移动2.57 mm和2.68 mm,双侧中切牙均平均向近中移动0.34 mm.双侧中切牙在水平向上无明显移动,左右侧第一磨牙均平均颊向移动0.96 mm和0.97mm,左右侧第二磨牙平均颊向移动1.01 mm和1.11 mm.双侧中切牙无明显伸长或压低,双侧第一磨牙均平均压低0.26 mm,左右侧第二磨牙分别平均压低0.37 mm和0.36 mm.双侧第一磨牙和第二磨牙均无明显颊腭向旋转.结论:无托槽隐形矫治器能有效地远中移动上颌磨牙,但会引起轻微的磨牙压低和前牙支抗丧失.     

Biomechanical rationale for intentionally inclined implants in the posterior mandible using 3D finite element analysis

PURPOSE: Since natural dental arches usually form Monson or Spee occlusal curvatures among the posterior teeth, they tend to incline in mesial and lingual directions. The purpose of this study was to examine the biomechanical rationale for placing implants according to these curvatures in the mandibular posterior region. MATERIALS AND METHODS: A 3-dimensional finite element model was created in which 2 implants were placed in the mandibular molar area. Stress distribution in the bone around the implants was analyzed under different distal implant inclinations. RESULTS: Stress in the cervical area of the mesial and distal implants and the surrounding bone was higher when the implants were placed parallel to each other compared to when the distal implant was placed with a mesial or mesiolingual inclination. DISCUSSION: The slightly smaller effect of a mesiolingual inclination compared to a mesial inclination can be explained by the large cantilever on the buccal side of the superstructure. CONCLUSION: Within the limitations of this study, it was suggested that there is a biomechanical rationale for placing implants in the posterior mandible area with a mesial inclination similar to that of natural teeth. It was also suggested that too much lingual inclination can put the implant at risk of overload.     

A study on the thickness of radicular dentine and cementum in anterior and premolar teeth

AIM: This study aimed to measure the thickness of radicular dentine and cementum in incisors, canines and premolars, and to develop geometric average models. METHODOLOGY: The roots of 220 extracted human teeth were sectioned in three horizontal parallel planes and measured using an optical microscope. For each cut surface buccal, lingual, mesial, and distal thickness of the root wall was measured. Mean values of the thickness at each location of each cut surface were calculated. The observed differences in thickness by tooth type, location, and section were compared by ANOVA and Student's t-test. RESULTS: Maxillary central incisors and maxillary canines had the greatest widths. In all teeth with a single root, the wall thickness were greater on the lingual side than the buccal side. Although differences between mesial and distal thicknesses were not statistically significant. CONCLUSIONS: Wall thickness varied greatly. The lingual surfaces of roots were larger. All roots had thin walls in the apical third.     

Force changes associated with different intrusion strategies for deep-bite correction by clear aligners

Objectives:To investigate the relationships among different intrusion patterns of clear overlay aligners and the corresponding orthodontic forces and to provide guidance for clinical treatment.Materials and Methods:Five sets of removable thermoplastic-formed aligners with the same thickness, designed for different intrusion procedures (G0 aligners as a control group, with no activation; G1 aligners for intruding canines; G2 aligners for intruding incisors; G3 aligners for intruding canines and incisors with the same activations; G4 aligners for intruding canines and incisors with different activation), were manufactured, and the corresponding intrusion forces were measured with a multiaxis force/torque transducer measurement system in real time.Results:With the same activation (0.2-mm intrusion) and rectangular attachments placed on the premolars and first molars, the canines experienced the largest intrusive force when intruded alone using G1 aligners. The canines received a larger intrusive force than incisors in G3. The incisors received similar forces in G2 and G3. First premolars endured the largest extrusive forces when all anterior teeth were intruded with G3 aligners. Extrusion forces were exerted on canines and lateral incisors when using G4 aligners.Conclusions:Aligners with different intrusion patterns exert different forces on incisors, canines, and premolars, and the forces were closely related to the designed activation, shape and position of the attachment and relative movement of the adjacent teeth.     

滑动法关闭下颌拔牙间隙的力学行为有限元分析

目的模拟临床加载力系统,研究滑动法内收下前牙过程中,不同方向载荷作用下,牙及弓丝力学行为的变化。方法建立含有托槽、弓丝、前后牙牵引钩的下牙列及下颌骨有限元模型。连接前后牵引钩上的点来确定矫治力的方向。并通过改变牵引钩高度来改变矫治力的作用点和方向。分析计算每一组加载力对牙的三维瞬间移动趋势、牙周膜的单元应力、弓丝的节点最大位移。结果前后牵引钩高度的变化与各牙角位移及牙周膜应力间均有相关性(P<0.01),各牙在不同后牙牵引钩高度,均随着前牙牵引钩高度变化而产生不同的移动。①随着前牙牵引钩高度的增加,中切牙、侧切牙的移动趋势逐渐由近中舌侧倾斜变为近中唇侧倾斜;而尖牙则向远中舌侧倾斜;第二前磨牙由近中颊侧倾斜变为近中舌侧倾斜;第一磨牙则由近中舌侧倾斜变为远中舌侧倾斜,且近中根比远中根舌向倾斜角度要大。②全牙弓牙周膜的最大应力始终出现在侧切牙的唇侧根尖1/3处;而尖牙、第一磨牙的牙周膜最大应力分别集中在牙槽嵴顶、根分叉处。结论在临床治疗中,可通过改变牵引钩的高度来实现前后牙的不同移动趋势,在弓丝上弯制不同的序列以更好地控制支抗牙。     

Change in dentition over 20 years from third decade of life

PurposePrevious studies have documented long-term, age-related change in the teeth, dental arches and occlusion. However, very few studies have investigated longitudinal age-related change in the dentition using 3-dimensional (3-D) measurement. The purpose of this study was to clarify age-related change in the dentition using a laser scanner.Materials and methodsWe used dental casts obtained from the same subjects in their twenties and forties. Subjects were selected based on near-normal occlusion. We investigated age-related variation in the dentition using 3-D measurement.ResultsAge-related change in the dentition was characterized by a decrease in maxillary and mandibular width, an increase in maxillary length, and a decrease in mandibular length. Measurement of angulation revealed that the maxillary canines and molars were mesially inclined. We observed labial inclination of the maxillary incisors, and lingual inclination of the mandibular incisors, as well as the maxillary and mandibular canines and molars. Overjet, overbite, and the irregularity index all showed an increase, while occlusal vertical dimension showed a decrease. Multiple regression analysis indicated that lingual inclination of the lower central incisors was related to an increase in the irregularity index, and that lingual inclination of the upper canines and decrease in occlusal vertical dimension of the anterior teeth were related to increased overbite.ConclusionThe present findings showed that age-related changes in angulation and inclination of each tooth should be taken into account when providing occlusal rehabilitation or post-orthodontic retention.     

Evaluation of photoelastic stress patterns produced by various designs of bilateral distal-extension removable partial dentures.

The results of this study showed that: 1. The design of a retainer with a mesial rest in conjunction with a buccal I-bar or a wrought-wire and cast lingual arm exhibited the most favorable distribution of vertically applied forces. 2. Retainer designs with a distal rest tend to move the clinical crown distally and the root mesially at the apex, resulting in horizontal forces in the bone. 3. Placing rests of distal-extension removable partial dentures more anteriorly provides an axis of rotation that directs applied forces in a more vertical direction. 4. The distal rest in conjunction with circumferential retainers developed greater horizontal forces within the supporting structures.     

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目的    探讨横腭弓在上颌唇向错位尖牙远中移动时对支抗的控制。方法    对2008年10月至2009年10月广东医学院附属南山医院口腔科收治的60例上颌尖牙唇侧错位患者。按就诊顺序随机分为试验组和对照组，每组30例。所有患者均用横腭弓加强支抗，横腭弓Ω曲朝向近中。试验组在错位尖牙舌窝黏舌侧扣，用弹力线将舌侧扣和Ω曲相连加力，在尖牙远移时实现支抗控制；对照组常规治疗。结果    试验组和对照组上颌磨牙均发生近中移动，其中对照组磨牙倾斜移动较大。模型测量： 矫治前后上颌尖牙（U3）牙尖间宽度的差值试验组较对照组小，试验组差值为（1.15 ±0.73）mm，对照组差值为（2.1 ±1.13）mm，两者比较差异有统计学意义（P < 0.05）。矫治前后上颌第一磨牙至腭大孔连线的距离（U6-PP）的差值试验组较对照组小，试验组差值为（1.17 ±0.39）mm，对照组差值为（2.05 ±0.37）mm，两者比较差异有统计学意义（P < 0.05）。结论    在尖牙远移过程中，横腭弓舌侧拉尖牙远移有利于控制尖牙宽度，保持弓形，减少后牙支抗的损耗。     

Evaluation of resistance form for prepared teeth

Resistance form of preparations for which castings were made in a large dental laboratory was evaluated. Each preparation was also evaluated for the placement of grooves. Evaluation of resistance form was done by grasping the casting between thumb and index finger and attempting to roll the uncemented casting off the die with finger pressure. Each preparation was tested for resistance form in all directions (buccal, lingual, mesial, and distal), from a fixed point of rotation. Evaluation was by tooth groups: incisors, canines, premolar, and molars. The preparations were found to have resistance form in 96% of the incisors, 92% of the canines, 81% of the premolars and only 46% of the molars. Only nine of 294 preparations evaluated had grooves. Mesial or distal grooves provided resistance to buccal and lingual dislodgment, and buccal or lingual grooves provided resistance to mesial and distal dislodgment.     

隐形矫治磨牙远移的三维有限元分析

目的　构建隐形矫治器上颌磨牙远移的生物力学研究模型,分析矫治体系的初始位移及应力分布特点,为该技术的临床应用提供指导。方法 建立隐形矫治上颌磨牙远移的三维有限元模型,在ANSYS软件中采用非线性有限元法通过数值仿真分析求得受力瞬间牙齿在牙周膜及周围牙槽骨等约束下的移动方式、牙套形变、牙周膜应力分布,并探索适宜的Ⅱ类牵引增强前牙支抗的必要性及适宜力值。结果 第二磨牙远移的同时伴有其牙冠远中倾斜、伸长及舌侧倾斜;其余牙表现为唇/颊倾、压低且位移量与距支抗牙距离成反比。牙周膜等效应力越靠近颈缘越大,距离第二磨牙越远越小,均小于牙周组织可承受最大应力。矫治器在第二磨牙处出现应力集中现象,位移峰值小于材料的弹性极限和拉伸极限强度。100 g Ⅱ类牵引可以有效抵抗前牙唇倾,300 g牵引力作用于牙列后超过牙周膜最大承受力值。结论 使用无托槽矫治技术远移磨牙不能实现单纯的整体移动且支抗牙有一定的支抗丧失,需要进行必要的支抗控制。100 g Ⅱ类牵引即可有效抵抗推磨牙带来的前牙支抗丧失,300 g牵引力作用下牙周膜受力过大,尽量避免使用。