正畸牙根吸收过程中牙根三维形态的MICRO-CT初步研究

目的了解不同的矫治力作用下牙根表面的三维形态学特征变化,探索正畸牙根吸收过程中矫治力值对牙根吸收的影响规律。方法选择11周龄的SD雄性大鼠22只,分别施加100g和30g近中移动上颌第一磨牙建立实验动物模型,以对侧同名牙作为对照牙。2周后处死动物,获得上颌第一磨牙及其周围牙槽骨。使用Skyscan 1172型Micro-CT扫描大鼠上颌第一磨牙,计算大鼠上颌第一磨牙近中根的表面凹陷体积并进行统计学分析。结果施加矫治力2周后,重力组与轻力组在牙根表面凹陷总体积上没有显著性差异,但是二者都显著高于对照组。在牙根上段近中面的凹陷体积上,轻力组显著高于重力组和对照组。在牙根下段远中面,重力组显著高于对照组（P〈0.01）。结论施加矫治力后,发生牙根吸收,但是在本实验的研究周期中,力值对牙根吸收的程度无明显影响,对吸收的部位有影响。在重力作用下,牙根吸收主要发生在牙根下段远中面。而在轻力作用下,牙根吸收主要发生在牙根上段近中面。     

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。     

牙齿移动过程中牙槽骨显微结构动态变化的微型CT研究

目的 通过微型CT探讨正畸牙齿移动过程中矫治力对牙槽骨骨小梁的影响规律,以期为正畸临床提供参考.方法 选择10周龄SD雄性大鼠10只建立实验动物模型,施加0.196 N矫治力,近中移动上颌第一磨牙,分别于加力前、加力后第3、7、14 d对大鼠上颌牙槽骨骨小梁进行微型CT扫描,计算骨体积分数、骨表面积体积比、结构模型指数...     

正畸牙齿移动过程中牙槽骨的Micro-CT形态学研究

目的了解不同矫治力作用下牙槽骨骨小梁显微结构变化情况,探索正畸过程中牙槽骨骨小梁结构变化规律,为正畸临床提供指导。方法选择11周龄sD雄性大鼠22只,分别施加100g和30g矫治力,近中移动上颌第一磨牙建立实验动物模型。2周后处死动物,获得上颌第一磨牙及其周围牙槽骨。使用Skyscan1172型Micro．CT扫描大鼠上颌牙槽骨骨小梁,计算骨小梁显微结构的各项参数并进行统计学分析。结果施加矫治力2周后,轻力组、重力组牙槽骨骨体积分数（BV／TV）都较对照组显著升高,重力组牙槽骨骨小梁间隙（Tb．Sp）比对照组明显减少（P〈0．05）,但重力组和轻力组之间没有显著性差别。结论在正畸矫治力产生的压应力作用下,牙槽骨进行相应的改建。     

近中移动上颌二磨牙后牙根吸收情况分析

目的：观察上颌第一磨牙拔除后正畸近中移动第二磨牙对牙根吸收的影响。方法：选取正畸拔除上颌第一磨牙病例17例,通过头颅定位侧位片测量第二磨牙近中移动的距离,应用头影测量软件分析矫治前后上颌第二磨牙的冠根比,确定牙根吸收的量,对17例病例治疗前后第二磨牙冠根比做t检验,对上颌第二磨牙近中移动距离和冠根比进行相关分析。结果：治疗前后上颌第二磨牙的冠根比差异均有统计学意义（P＜0．01）,移动距离与冠根比呈正相关。结论：上颌第二磨牙近中移动会造成牙根吸收,但是吸收量较少,在临床上是可以接受的。牙齿的移动距离是影响牙根吸收的重要因素。     

骨转换率对大鼠正畸牙齿移动量及牙根吸收的影响

目的:研究在不同骨转换率的条件下,大鼠牙齿移动过程中牙齿移动量及对牙根吸收的影响。方法:健康成年雄性威斯塔大鼠30只,体重180～220g。随机分成3组:高骨转换率组,低骨转换率组,正常对照组。前2组通过20d甲状腺片和丙硫氧嘧啶灌胃得到高骨转换率和低骨转换率组动物模型。左侧上颌第一磨牙加力21d。在处死动物前15d及2d添加骨标志物。拍X线片测量牙齿移动距离及牙根长度。结果:高骨转换率组的大鼠正畸牙齿移动的距离长,牙根最长。结论:骨转换率对正畸牙齿移动量及牙根吸收有影响。骨转换率高则大鼠牙齿移动量大,牙根吸收少,反之大鼠牙齿移动量小,牙根吸收多。     

灌服川续断水煎液对大鼠正畸牙移动的影响

目的 研究灌服川续断水煎液对大鼠正畸牙移动的影响。方法 选择48只SPF级Wistar大鼠,随机分2组,每组24只,于上颌一侧第一磨牙与上切牙之间结扎正畸螺旋弹簧,建立大鼠正畸牙齿移动实验模型。实验组每日灌服6g/kg川续断水煎液;对照组每日灌服3ml生理盐水。两组动物于正畸加力7、14、21、28d后分批处死,取上颌磨牙及牙周组织,测量上颌第一磨牙近中移动距离并行统计学分析。结果 正畸加力7d,实验组大鼠第一磨牙近中移动距离与对照组无统计学差异(P>0.05)。正畸加力14、21、28d,实验组大鼠第一磨牙近中移动距离明显大于对照组(P<0.05)。结论 川续断能够加速正畸牙齿的移动速度。     

Sprague-Dawley 大鼠磨牙早期牙根发育的显微CT研究

目的：研究发育中Sprague-Dawley大鼠第一磨牙牙根发育的形态学特征。方法健康雄性Sprague-Dawley 大鼠30只,随机分成6组,每组5只,分别于出生后26d、33d、40d、47d、54d、70d处死后行显微CT(西门子,层距18μm)扫描,然后通过Mimics15．0进行三维重建,观察不同时间点上颌右侧第一磨牙的三维形态,并对其磨牙体积和近中牙根的长度进行测量分析。结果大鼠上颌第一磨牙有5个牙根,近中颊侧牙根较细而短,发育提前完成。从26d到70d,第一磨牙牙根不断伸长,根尖孔逐渐缩窄。磨牙体积从26d到54d不断增加,在70d体积出现了一定减少。结论大鼠上颌第一磨牙牙根发育持续到70d,提示牙齿移动实验设计时要考虑第一磨牙的发育阶段。     

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。     

上颌窦底对上颌第一磨牙正畸移动影响的锥形束CT研究

目的:利用锥形束计算机断层扫描技术评估上颌第一磨牙牙根与上颌窦底间不同的解剖位置关系对正畸减数矫治时第一磨牙近中整体移动及牙根吸收的影响。方法:纳入44例减数前磨牙完成正畸矫治的成年患者,根据上颌第一磨牙牙根与上颌窦的接触关系分为两组：各牙根均未与窦底接触(isolate from maxillary sinus, I...     

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.     

釉基质蛋白衍生物对大鼠牙移动后复发和牙根修复的影响

目的:观察釉基质蛋白衍生物对大鼠正畸牙移动后早期复发和牙根吸收的影响.方法:选用20只10周龄雄性SD大鼠,实验组和对照组各10只,在左上第一磨牙施加100 g力,使其近中移动,加力14d后拆除装置.自拆除加力装置起,实验组局部注射釉基质蛋白衍生物,对照组不注射任何药物.分别于拆除装置后当天及第14天分别行Micro-CT活体扫描,分析牙根吸收陷窝以及牙移动距离的变化.采用SPSS19.0软件包对数据进行统计学分析.结果:拆除装置14 d后,实验组与对照组牙根吸收陷窝体积修复量分别为(0.0295±0.0052) ×1 07 μm3、(0.0189±0.0086)×107 μm3;牙移动后复发距离及复发百分率分别为(0.089±0.005)mm、(64.76±3.63)％和(0.127±0.010)mm、(92.28±1.90)％.统计学分析表明,拆除装置14 d后,牙根吸收陷窝体积修复量、牙移动后复发距离及复发百分率均有显著差异(P＜0.05).结论:一定浓度的釉基质蛋白衍生物可在一定程度上加强大鼠正畸移动后牙根吸收后修复效应,减弱牙移动后早期复发.     

Effects of different force magnitudes on corticotomy-assisted orthodontic tooth movement in rats

Objectives:To investigate the effects of light and heavy forces with corticotomy on tooth movement rate, alveolar bone response, and root resorption in a rat model.Materials and Methods:The right and left sides of 40 male Wistar rats were randomly assigned using the split-mouth design to two groups: light force with corticotomy (LF) and heavy force with corticotomy (HF). Tooth movement was performed on the maxillary first molars using a nickel-titanium closed-coil spring delivering either 10 g (light force) or 50 g (heavy force). Tooth movement and alveolar bone response were assessed by micro–computed tomography (micro-CT) at day 0 as the baseline and on days 7, 14, 21, and 28. Root resorption was examined by histomorphometric analysis at day 28.Results:Micro-CT analysis showed a significantly greater tooth movement in the HF group at days 7 and 14 but no difference in bone volume fraction at any of the observed periods. Histomorphometric analysis found no significant difference in root resorption between the LF and HF groups at day 28.Conclusions:Heavy force with corticotomy increased tooth movement at days 7 and 14 but did not show any difference in alveolar bone change or root resorption.     

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.     

Intermittent force in orthodontic tooth movement

A single orthodontic activation lasting one hour can initiate tooth movement. The purpose of this study is to examine tooth movement, osteoclasts, and root resorption in rats following several one-hour activations. Rats (n = 144) were randomly assigned to intermittent (multiple activations of 1 hr/day), continuous, and sham appliances. Twelve rats were killed at 3, 5, 7, and 14 days. Tooth movement, osteoclasts, osteoclast %, and root resorption % were quantified. Continuous force moved molars mesially at days 3 and 14 (p < 0.05), but intermittent and sham did not. Intermittent and continuous force increased osteoclast numbers at days 3, 5, and 7 (p < 0.05). Continuous force increased osteoclast surface on days 3 and 14 (p < 0.05). Continuous force increased root resorption at days 5, 7, and 14 (p < 0.05). These results demonstrate that orthodontic force for one hour in 24 stimulates osteoclasts at compression sites but does not stimulate tooth movement or root resorption.     

Effect of continuous versus intermittent orthodontic forces on root resorption: A microcomputed tomography study

Objectives:To compare the extent of root resorption and the amount of tooth movement between continuous orthodontic force and intermittent orthodontic force that was activated in a similar way to a 4-week orthodontic adjustment period.Materials and Methods:Twenty-five patients who required the extraction of upper first premolars were recruited in this study. A buccally directed continuous force of 150 g was applied to the upper first premolar on one side for 15 weeks. A buccally directed intermittent force (28 days on, 7 days off) of the same magnitude was applied to the contralateral first premolar. The teeth were extracted at the end of the experimental period and processed for volumetric evaluations of resorption craters. The degree of tooth movement and rotation were measured on the study models.Results:Continuous force application displayed significantly higher root resorption volume than the intermittent force application (P < .05), particularly on the buccal and lingual surfaces (P < .05) and the middle third of the root (P < .01). There was more tipping and rotational movement in the continuous force group.Conclusions:In a 4-week orthodontic adjustment period, intermittent force significantly reduced the amount of root resorption compared with continuous force. Although there was less degree of tooth movement with intermittent force, unwanted rotational movement was avoided. This is crucial in patients who are predisposed to orthodontically induced inflammatory root resorption, and the use of this intermittent regimen should be considered.     

Periodontal response to experimental tooth movement by interrupted orthodontic force in rats

The upper first molars of Wistar rat were moved experimentally using an expansion screw in order to clarify whether an interrupted orthodontic force that maintains the blood circulation in compressed periodontal ligament (PDL) can cause efficient tooth movement without pathological damage.In the 30-μm group with moving distance of one-third of PDL width, degenerating tissue with toluidine blue staining and appreciable root resorption were not seen during the experimental period. On the other hand, in the 60-μm group with moving distance of two-third of PDL width degenerating tissue and severe root resorption appeared. On observation of bone formation using Villanueva fluorescent staining, a thick labeling line was observed on the tension side in both experimental groups.In statistical analysis about the ratio between mesial and distal PDL areas, expressing expansion rate of mesial PDL, there was no significant difference between 30-μm and control groups, except an experimental period of day 11. In contrast, significant differences were seen between 60-μm and control groups in 23–31 days after tooth movement.From these results, it is evident that the interrupted force that induces tooth movement within a distance of approximately one-third of PDL width enables tooth movement without toluidine blue-stained degenerating tissue, regarded as pathological damage, and promotes bone formation on the tension side.     

Effects of calcitonin on orthodontic tooth movement and associated root resorption in rats

Objectives: Our main aim was to evaluate the effects of calcitonin (CT) on orthodontic tooth movement (OTM) and orthodontic root resorption in a rat model.

Material and methods: Eighty male Wistar rats were randomly divided into five groups. Rats in the negative control group were not given any appliances or injections. All the remaining rats were used to establish a model of OTM. The positive control group were then injected with normal saline, while rats in the three experimental groups were injected with 0.2?IU, 1?IU or 5?IU/kg/day CT. Nickel-titanium closed-coil springs were used to deliver an initial 50?g mesial force to the left maxillary first molar for 14 days in rats in the positive control group and the experimental groups. Each group was randomly subdivided into two groups, one for analysis of tooth movement, tissue changes and tartrate-resistant acid phosphatase (TRAP)-positive cells in alveolar bone, the other to examine root resorption by scanning electron microscopy.

Results: The OTM distance, the number of force-induced osteoclasts and root resorption areas were significantly decreased in CT-injected rats in a dose-dependent manner.

Conclusions: Administration of CT reduces the root resorption area and may therefore be effective as a novel adjunctive orthodontic approach to diminish undesired tooth movement via enhancing anchorage or preventing relapse after OTM.     

Celebrex offers a small protection from root resorption associated with orthodontic movement

Tooth movement results from alveolar bone resorption/deposition following application of orthodontic forces, and root resorption can be an undesirable complication associated with this process. No treatment for external root resorption is available to date. OBJECTIVE: To determine if COX-2 inhibitors like Celebrex are effective in protecting root resorption associated with orthodontic forces. METHODS: A force of 80 grams was applied to the left maxillary first molars of 7-week-old female Wistar rats using nickel titanium closed coil springs attached to the cervical area of the incisors with 0.010 stainless-steel ligature wires. Twenty animals were divided into three experimental groups: one receiving no treatment, the second receiving 25mg/kg, and the third receiving 50 mg/kg of celecoxib (Celebrex) in their drinking water. Rats were maintained on a soft diet and euthanized two weeks after initial placement of the force. Paraffin-embedded sections of the right (control) and left (experimental) maxillae were stained with H&E and the areas of root resorption were examined by counting the number of lacunaes in the roots. RESULTS: No difference in the distance of tooth movement (0.5 mm/two weeks) was seen in all three groups. The rats that received the low dose of Celebrex showed no statistically significant difference in root resorption than that of the rats that received no dose. The rats that received the high dose of Celebrex showed a lower number of lacunaes (mean = 3.5) than that of the control group (mean 10.2; p=0.02). CONCLUSIONS: Administration of Celebrex during the application of orthodontic forces does not interfere with tooth movement and appears to offer some slight protection against root resorption.     

偏侧咀嚼对正畸牙移动影响的实验研究

目的通过建立偏侧咀嚼大鼠模型,探讨偏侧咀嚼对正畸牙移动过程的影响。方法选择30只6～8周龄,（250±10）g,雄性SD大鼠,随机分为实验组与对照组,每组各15只。通过拔除实验组大鼠右下颌所有磨牙使右上颌第一磨牙丧失咬合接触建立大鼠偏侧咀嚼动物模型,同时,在两组大鼠双侧上颌切牙和第一磨牙间放置镍钛拉簧,初始力值为50g,近中移动磨牙。分别于第0、3、7、10、14天测量大鼠上颌第一磨牙近中移动的距离并通过HE染色观察大鼠上颌第一磨牙牙周组织形态学变化。结果各时间点代偿性咀嚼增强侧牙移动速率均小于对照组（P〈0.05）,牙周组织变化与对照组相似;失咬合侧牙移动速率大于对照组（P〈0.05）,牙周组织出现退行性改变;但三种咬合状态下牙齿移动速率曲线均表现为瞬时运动、迟滞期及后期移动三个阶段。结论动物实验证实偏侧咀嚼引起正畸牙牙周组织发生相应改变最终影响牙移动速率,但无论牙移动速率快慢,牙移动均符合正畸性牙移动的一般规律。