尖牙受力后龈沟液中碱性磷酸酶水平的变化

目的:通过分析上颌尖牙受不同作用力后龈沟液(GCF)中的碱性磷酸酶(ALP)水平的动态变化规律,间接了解牙齿受机械力作用后牙周组织改建的生化反应过程。方法:选择28例正畸患者为研究对象,随机分成4组。分别对其右侧上颌尖牙施加50 g、100 g、150 g、250 g的远中移动初始力,左侧上颌尖牙不加力为对照组。分别在加力前、加力后24 h、48 h、72 h、7 d、14 d、21 d和28 d时收集尖牙近、远中龈沟内GCF,并检测ALP含量。结果:不同时间点、不同力值下GCF中ALP水平变化差别有统计学意义(P<0.001),而牙齿近远中侧GCF中ALP水平变化差别无统计学意义。结论:GCF中ALP的水平与正畸力大小及力的持续时间密切相关;GCF中ALP含量的变化可以作为分析临床正畸加力大小是否合适的参考指标之一。     

不同正畸力值作用下龈沟液中天冬氨酸转氨酶水平的变化

目的:通过分析上颌尖牙受不同作用力后龈沟液(GCF)中的天冬氨酸转氨酶(Aspartate aminotrans-ferase,AST)水平的动态变化规律,间接了解牙齿受机械力作用后牙周组织改建的生化反应过程。方法:选择正畸患者28例为研究对象,随机分成4组。分别对4组患者的右侧上颌尖牙施加50g、100g、150g、250g的远中移动初始力,左侧上颌尖牙均不加力。分别在加力前、加力后1、2、3、7、14、28d时收集尖牙近、远中龈沟内GCF,SYS-MEX全自动生化分析仪检测AST含量。结果:不同时间点、不同力值下GCF中AST水平变化差别有统计学意义(P<0.001),而牙齿近远中侧GCF中AST水平变化也有明显的无统计学意义。结论:GCF中AST的水平与正畸力大小及力的持续时间密切相关;GCF中AST含量的变化可以作为分析临床正畸加力大小是否合适的参考指标之一。     

不等力值远中移动尖牙的比较研究

目的 研究100 g力与150 g力远中移动尖牙后牙齿移动距离、根尖及根周硬组织的变化.方法 用OPAK直丝弓矫治技术对25名青少年患者在.18×.025的方丝上,应用Ni-Ti螺旋弹簧分别以初始100 g及150 g力牵引尖牙向远中,四周后分别用游标卡尺及Digora分析法比较牙齿移动距离、牙根长度及牙槽骨高度及密度的变化.结果 应用100 g力及150 g力移动尖牙向远中一月,两者的尖牙移动距离有显著性差异(p＜0.01),150 g力侧移动距离大于100 g力侧.而牙根长度、牙槽骨高度及密度无显著性差异(p＞0.05).结论 临床上OPAK矫治器在0.018×0.025英寸不锈钢方丝上应用150 g力移动尖牙向远中是行之有效而且是安全的.     

大鼠正畸性牙根吸收及牙齿移动差异的研究

目的建立大鼠正畸性牙根吸收模型,比较一个加力周期内不同加力时间及不同加力力值时大鼠牙齿的移动差异及牙根吸收情况。了解时间、力值与牙齿移动及牙根吸收的关系。方法选择月龄相同,体质量相近的SD雄性成年大鼠建立正畸牙移动模型,按不同加力时间分为1、3、5、7、10、14d组,按加力大小分为40g、60g、80g力组。测量不同组别正畸牙移动量,采用连续切片观察牙根吸收情况。结果各组牙齿移动距离不同;牙根吸收主要表达在根中1/3区域;吸收程度与加力时间及力值有关。结论1、成功建立大鼠正畸性牙根吸收模型。2、不同加力时间及不同力值各组牙齿移动距离存在显著差异。3、不同加力时间及不同力值组牙根吸收存在规律性。     

在持续轻力下的人类牙齿移动

传统的正畸治疗通常应用100克以上的力后移尖牙,而牙齿移动的产生有一个约21天的滞后期。本文研究发现通过应用轻力,牙齿移动的产生不发生滞后,且速度在临床上很显著。7个受试者(2男5女,12～16岁)参加了84天的研究。拔除14、24后,每侧上颌的尖牙、第二双尖牙、第一磨牙上应用片段垂直曲,曲高度与牙抗力中心一致,用弹簧施加持续力。随机于一侧尖牙施力18克,另一侧60克。调整力值,使每颗尖牙产生相等的压强,尖牙远中面的平均压强分别是4和13Ｋｐａ,力矩/力为9到13ｍｍ。牙齿在直线及旋转三维中的移动应用三轴测量显微镜测量,头三天隔天取一次…     

个体因素与牙齿移动速率关系的初步探讨

目的 :初步探讨个体因素与牙齿移动速率的关系。方法 :利用 15 0克相对恒定力 (由 5毫米长的螺旋弹簧产生 )及 15 0克渐衰力(由 3个圈长的橡皮链产生 )分别移动同一牙弓内的尖牙。每四周复诊一次 ,每次复诊 ,取模 ,螺旋弹簧加力至 15 0克 ,橡皮链因力值衰减更换新的 ,加力至 15 0克 ,在模型上用电子数显卡尺测量尖牙远移距离 ,对所测数据作方差分析。所选病例为需双侧第一双尖牙减数矫治的患者 ,年龄 12至 14岁 ,平均 13.7岁 ,骨龄 78% 82 %。结果 :无论是使用相对恒定力还是渐衰力远中牵移尖牙 ,在尖牙移动的速率方面都存在明显的个体差异 ,上尖牙相对恒定力侧最大速率为 1.6 1mm/ 2 8天 ,最小为 0 .90mm/ 2 8天 ,渐衰力侧分别为 1.10mm/ 2 8天和 0 .5 6mm/ 2 8天 ;下尖牙相对恒定力侧的最大和最小速率分别为 1.31mm/ 2 8天和 0 .70mm/ 2 8天 ,橡皮链侧分别为 0 .93mm/ 2 8天和 0 .4 7mm/ 2 8天 ,分别具有非常显著的统计学差异。结论 :在相同的正畸力作用下 ,牙齿移动速率因人而异。与力的持续时间相比 ,个体差异也是影响牙齿移动速率的一个重要因素。     

CD矫治器载荷值影响尖牙和磨牙应力分布和位移的三维有限元研究

目的研究Carriere Dista／izer矫治器（CD矫治器）5种加载力值下上颌尖牙和磨牙应力分布及位移。方法构建CD矫治器作用模式的三维有限元模型,设载荷方向为给平面下20°,代表以下颌第一磨牙做Ⅱ类牵引之起点向前上方止于尖牙。设定加载力值分别为50、100、150、200、250g,分析5种力值下,上颌尖牙和磨牙应力分布及位移的差异。结果应力和位移均与载荷力值成正比。但5种力值中,2130g力值下,尖牙和磨牙的应力和位移增加不多;250g力值下,无论尖牙还是磨牙,其牙颈部的应力分布和位移明显非等差地高于其他4种载荷力值下的应力分布和位移。结论不同载荷力值作用于上颌尖牙和磨牙时．其应力和位移的分布规律大致一致,且应力和位移的大小基本随载力值的递增而增加。150g与200g载荷力值下的应力和位移趋同,提示其可能是CD矫治器较理想的牵引力。     

Micro-CT活体观察大鼠牙齿移动及复发过程的实验研究

目的:Micro-CT活体扫描连续观察不同矫治力引起的牙齿移动及复发的规律。方法:选择10周龄SD大鼠15只随机分成3组。对大鼠左侧上颌第一磨牙分别施加20 g、50 g、100 g的矫治力,持续加载14 d后卸载。在加力后的0、3、7、10、14 d和停止加力后3、7、10、14、28、42 d用Micro-CT对大鼠进行活体扫描,测量每个时间点牙齿移动的距离。结果:在加力后的0～3 d各组的磨牙都发生明显的近中移动,第3～10天,牙移动缓慢,第10天时20 g和100 g组移动距离快速增加。20 g组在矫治力去除后的0～3 d复发最多,50 g和100 g组在0～7 d复发最多,28 d几乎完全复发。结论:加载矫治力后牙齿呈现快速、缓慢、快速的移动规律,且轻力引起的牙移动更多。拆除加力装置的初期复发的最快,牙齿移动距离越大,复发越快。     

不同Ⅱ类牵引模式对无托槽隐形矫治磨牙远移作用的比较：三维有限元研究

目的:构建隐形矫治器上颌磨牙远移中两种Ⅱ类牵引的生物力学研究模型,分析矫治体系在不同加力模式、不同牵引力大小作用下的初始位移及应力分布特点,为该技术的临床应用提供参考。方法:建立隐形矫治推上颌磨牙向远中及两种Ⅱ类牵引模式(牙套加力组与牙齿加力组)的三维有限元模型,采用非线性有限元法分析2种不同加力方式及5种不同载荷(100 g、150 g、200 g、250 g、300 g)下的牙齿移动方式、牙套形变、牙周膜应力分布等,比较其增强前牙支抗效果的异同。结果:不同力值不同加力方法下所有组Ⅱ类牵引均可以使前牙内收,抵抗磨牙远中移动过程造成的前牙支抗丧失,但其牙齿应力分布、牙套形变效果不同：牙齿加力组集中在直接受力的尖牙上,分布不均匀;牙套加力组分布更均匀,随距尖牙距离由近到远逐渐减小,但总体大小较牙齿加力组大。牙周膜等效应力除300 g牙套加力组[(2.87×10 -2) MPa]过大外,其余各组均在牙周膜可承受范围内。 结论:100 g的Ⅱ类牵引即可抵抗磨牙远移反作用力造成的前牙支抗丧失,300 g牙套加力作用下的牙周膜受力过大,尽量避免使用。     

不同Ⅱ类牵引模式对无托槽隐形矫治磨牙远移作用的比较：三维有限元研究

目的:构建隐形矫治器上颌磨牙远移中两种Ⅱ类牵引的生物力学研究模型,分析矫治体系在不同加力模式、不同牵引力大小作用下的初始位移及应力分布特点,为该技术的临床应用提供参考。方法:建立隐形矫治推上颌磨牙向远中及两种Ⅱ类牵引模式(牙套加力组与牙齿加力组)的三维有限元模型,采用非线性有限元法分析2种不同加力方式及5种不同载荷(100 g、150 g、200 g、250 g、300 g)下的牙齿移动方式、牙套形变、牙周膜应力分布等,比较其增强前牙支抗效果的异同。结果:不同力值不同加力方法下所有组Ⅱ类牵引均可以使前牙内收,抵抗磨牙远中移动过程造成的前牙支抗丧失,但其牙齿应力分布、牙套形变效果不同：牙齿加力组集中在直接受力的尖牙上,分布不均匀;牙套加力组分布更均匀,随距尖牙距离由近到远逐渐减小,但总体大小较牙齿加力组大。牙周膜等效应力除300 g牙套加力组[(2.87×10 -2) MPa]过大外,其余各组均在牙周膜可承受范围内。 结论:100 g的Ⅱ类牵引即可抵抗磨牙远移反作用力造成的前牙支抗丧失,300 g牙套加力作用下的牙周膜受力过大,尽量避免使用。     

Force magnitude and duration effects on amount of tooth movement and root resorption in the rat molar

OBJECTIVE: To test the hypothesis that there is no difference in the effect of different continuous moderate to very heavy forces on root resorption or amount of tooth movement. MATERIALS AND METHODS: In the study, 10, 25, 50 and 100 g mesial force were applied to the maxillary first molars of rat using nickel titanium closed-coil springs for 3 days, 14 days, and 28 days. The molars were extracted and the surface areas of the root resorption craters were measured using scanning electron microscope. The depths of the root resorption craters were measured using a three-dimensional laser scanning microscope. Tooth movement of the maxillary first molar was measured in relation to the maxillary second molar on digitized lateral cephalometric radiographs. RESULTS: Three days after force application, the tooth movement was not proportionally related to force magnitude. However, 14 days of force application resulted in significantly more tooth movement in the 10, 25, and 50 g force groups than in the 100 g force group. A force application of 10 g produced significantly more tooth movement at 28 days than all the other three force applications. The largest and deepest resorption craters were observed in the disto-buccal root followed by disto-palatal, middle-buccal, middle-palatal, and mesial root. Root resorption and tooth movement increased over time from 3 to 28 days. As heavier forces were applied, greater root resorption occurred. CONCLUSION: The hypothesis is rejected. The light mesially oriented forces, as applied in this study, produced more tooth movement and less root resorption compared with heavier forces.     

Clinical evaluation of a low-friction attachment device during canine retraction

OBJECTIVE: The present study used a split-mouth design to compare the amount of canine movement and the retraction time between brackets with Clear Snap and brackets with stainless steel ligature wires for three different levels of retraction force. MATERIALS AND METHODS: A sample of 30 patients was used. After initial leveling, the canine was retracted using a 50-g (n = 10), 100-g (n = 10), or 150-g (n = 10) closed-coil spring. The canine on one side was chosen at random, and Clear Snap was attached to the bracket during the retraction period. The other side was used as a control. The amount of canine retraction was measured with a digital vernier caliper. Statistical analysis was performed by analysis of variance. RESULTS: The average canine retraction time was approximately 2 to 3 months less in all experimental groups (50, 100, and 150 g) compared to the control group. In the control group, 150 g resulted in a shorter duration of canine retraction compared to 50 g. There was no significant difference in the duration of canine retraction among the experimental groups. A greater amount of mean total canine movement was observed in all experimental groups compared to the control groups. CONCLUSION: A shorter duration of canine retraction time was observed with Clear Snap attached when compared with the control. The authors suggest that with the use of Clear Snap, less than 50 g of force may effectively retract a canine.     

种植体支抗移动幼犬牙齿的实验研究

目的：探讨微型种植体移动生长发育期幼犬牙齿的特点,为正畸临床上青少年正畸支抗的选择及设计提供参考。方法：植入直径为1.3mm的微型种植体,分别采用200g及300g的力,拉上颌尖牙向远中移动;利用上颌第一磨牙采用300g力移动直径分别为1.3mm和1.6mm的微型种植体。检测3个月后尖牙的远中移动情况,不同加载力,不同直径的微型种植体的稳定情况。结果：直径1.3mm的微型种植体加载200g及300g力3个月后的位移量差别显著（p〈0.01）、上颌尖牙明显位移,位移量差别显著（p〈0.001）;加载300g力后,直径1.3mm的微型种植体略有松动,直径1.6mm的微型种植体几乎没有松动,不同直径种植体的相对位移量差异有显著性（0.02%@ 1003-1634     

拔牙区骨改建对邻牙移动速度的影响

目的　本研究通过对拔牙创的骨改建进程及矫治力对牙齿移动的影响进行研究,为临床医生选择理想的矫治力和牙齿移动时机,缩短矫治时间提供依据。方法　取SD大鼠36只,随机分为3组,全麻下拔除一侧上颌第一磨牙,3月后拔除另一侧上颌第一磨牙。在拔牙后不同的时间制作口内矫治器,分别以0·30、0·60、1·36 N的力牵上颌第二磨牙向拔牙区移动,分别在施力前及施力后的第1、3、5、7、10、14天拍摄X线片,利用图像处理技术, 测量牙齿移动距离,以置入的拔髓针校正放大率。结果　①牙齿向新鲜拔牙区移动的速度明显大于向已愈合拔牙区移动的速度。②无论向新鲜拔牙区移动还是向已经愈合的拔牙区移动,0·30 N力组牙齿移动的距离在各时间点与0·60 N、1·36 N力组牙齿移动的距离之间存在显著的统计学差异;而0·60 N与1·36 N力组牙齿移动的距离之间基本上从第5天开始差别不大。③加力后牙齿移动周期一般包括三个阶段:瞬时运动;迟滞期;后期移动阶段。大约在第14天时,由于矫治力衰减,牙齿停止移动。结论　①牙齿向新鲜拔牙区移动速度快,而向已经愈合的拔牙区移动速度慢。②在矫治过程中,中等力较为合适;即使使用较大的力,也不一定引起较大的牙齿移动。     

Effects of different types of tooth movement and force magnitudes on the amount of tooth movement and root resorption in rats

Objective:To investigate differences in the amount of tooth movement and root resorption that occurred after tipping and bodily movement of the maxillary first molar in rats.Materials and Methods:Ten-week-old female Wistar rats were divided into two groups according to type of tooth movement and subdivided into four subgroups according to the magnitude of applied force. Nickel-titanium closed-coil springs exerting forces of 10, 25, 50, or 100 g were applied to the maxillary left first molars to induce mesial tooth movement. We designed a novel orthodontic appliance for bodily tooth movement. Tooth movement distance and root resorption were measured using microcomputed tomography and scanning electron and scanning laser microscopy.Results:The amount of tooth movement in the bodily tooth movement group was less than half that in the tipping tooth movement group. The greatest amount of tooth movement occurred in the 10-g tipping and 50-g bodily tooth movement subgroups, and the amount of tooth movement decreased with the application of an excessive magnitude of force. Conversely, root resorption increased when the heavier orthodontic force was applied in both groups. Root resorption in the tipping tooth movement group was approximately twice that in the bodily tooth movement group.Conclusions:Root resorption in the tipping tooth movement group was more pronounced than that in the bodily tooth movement group. Although the amount of tooth movement decreased when extremely heavy forces were applied, root resorption increased in both the tipping and bodily tooth movement groups in rats.     

Evaluation on the movement of endosseous titanium implants under continuous orthodontic forces: an experimental study in the dog

Objectives: The purpose of this study was to evaluate the movement of pure titanium implants under different continuous forces in the edentulous alveolar ridge. Material and methods: Four pairs of titanium implants were inserted into the right maxillary and mandibular post‐extraction edentulous ridge of the experimental dog. Three different levels of continuous force (100, 200, and 500 g) were loaded onto three pairs of adjacent implant abutments using a memory Ni–Ti coil spring for up to 6 months and the remaining two implant abutments as the control group received no force. The positions of implant abutments were observed and the distances between the implants abutment at the top, middle and base levels were measured at the 0th, 2nd, 3rd, 6th and 8th month of the follow‐up period. Results: There was no significant change in the distances between adjacent abutments loaded with 100 or 200 g continuous forces throughout the entire study period. However, significantly more movement of implant abutments was noted in the 500 g pair after the 3rd month of loading when compared with the 200 or the 100 g pair (both P<0.001). This change further increased at the 6th month (P<0.001, 0.01, respectively). Moreover, the difference in the measurements at the top, middle and base level indicated that the two adjacent implants moved in a tipping manner in the 500 g pair after 3 and 6 months of loading. Conclusion: The osseointegrated implants remained stable and rigid with a pulling force of 100 and 200 g after 6 months of loading. However, when the force reached 500 g, the implants moved in an inward‐tipping pattern. The results suggested that endosseous titanium implants might not necessarily be rigid anchorages under all circumstances.     

改良型Ⅱ类颌间牵引致下颌支抗牙受力变化分析

目的 研究改良型Ⅱ类颌间牵引的支抗磨牙受力情况及移动特点,分析其相关影响因素.方法 参考Typodont模型原理,设汁制作出结构简化的实验牙受力、移位测量装置.实验对象依受力点、受力大小及受力角度不同分为4个实验组,每组3颗样本牙.1组:受力点位于下颌实验牙近中舌侧尖,力值150g;2组:受力点位于下颌实验牙远中舌侧尖,力值150g;3组:受力点位于下颌实验牙近中舌侧尖,力值100 g;以上3组上颌受力点均位于上颌尖牙,施力角度约30°.4组:受力点位于下颌实验牙近中舌侧尖,力值100 g,上颌受力点位于上颌双尖牙,施力角度约60°.选取实验牙近中颊尖、远中尖、近中舌尖、远中舌尖最高点为固定标志点,以测量装置上的基准点线为参照点线,测量实验前后下颌实验牙标志点与基准点线间的距离,对所得数据进行t检验分析.结果 4组下颌实验牙在牵引力作用下均有明显的近中向及颊向移位,同时伴(牙合)向伸长.近中向位移值范围为0.50～3.33 mm,颊向位移值范围为2.67 ～6.17 mm,垂直向位移值范围为0.22 ～4.00 mm.位移大小与牵引力大小有关,1组和3组差异有统计学意义(P＜0.05).牵引力角度的变化可影响实验牙移动模式,角度增加,实验牙以颊向及(牙合)向移位为主,同时冠远中向旋转减轻.结论 改良型Ⅱ类颌间牵引力引起下颌实验牙三维移动,以近中及颊向移位为主,受力点的位置、牵引力的大小与角度可影响支抗牙的移动模式.