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。     

大鼠正畸牙齿在不同骨转换率下牙周组织变化

目的:研究在不同骨转换率的条件下,大鼠牙齿移动过程中,牙周组织形态的变化。方法:健康成年雄性威斯塔大鼠30只,体重180～220 g。随机分成3组:高骨转换率组,低骨转换率组,正常对照组。高骨转换率组将甲状腺片研末,0.9%氯化钠注射液配制成2 mg/mL混悬液。每只大鼠2 mL/d灌胃。低骨转换率组动物1%丙硫氧嘧啶2mL/d灌胃,对照组蒸馏水2 mL/d灌胃。20 d后,大鼠麻醉下加力,加力21 d后处死。组织学切片,HE染色,光镜下观察。结果:各组对照侧牙周膜排列整齐,牙槽骨表面破骨细胞少见。没有明显成骨及破骨现象,张力侧成骨细胞、成纤维细胞,功能旺盛;压力侧破骨细胞增多,成纤维细胞,间充质细胞、活跃的巨噬细胞增多。高骨转换率组表现更强的组织反应性。结论:高骨转换率能增加牙周组织反应,有利于正畸牙齿的移动。     

两种二膦酸盐对大鼠正畸源性牙根吸收及牙移动影响的对比研究

目的探讨第2代与第3代膦酸盐类在正畸过程中对大鼠牙齿移动距离和牙根吸收的影响,为临床正畸牙齿移动中预防牙根吸收提供参考。方法选取96只6周龄无特定病原体动物级Wistar雌性大鼠建立正畸牙移动模型,正畸牙齿大鼠模型按随机数字表随机分为帕米膦酸钠组与伊班膦酸钠组各48只;分别于上颌左侧第一磨牙近中腭侧黏骨膜下注射50μL帕米膦酸钠、伊班膦酸钠,每3天1次。正畸加力第3、7、14天时每组分别处死16只大鼠,随机选择其中8只测定牙齿移动距离并制作牙周组织学切片测定牙根吸收指数,另外8只采用扫描电镜观察牙根吸收情况。实验数据用PASW statistics18软件进行处理。结果第3、7、14天,两组牙齿移动距离均逐渐增加,但两者之间无显著差异;帕米膦酸钠组牙根吸收指数在第3、7、14天比伊班膦酸钠组相对较大,但两者间的差异无统计学意义。结论局部注射第2代膦酸盐类与第3代膦酸盐类对大鼠正畸源性牙齿移动和根吸收的影响大致相同,两者均可减缓牙齿移动的速度和减轻牙根吸收的程度。     

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目的探讨伊班膦酸钠对正畸源性牙根吸收的影响。方法本实验于2011年6月至2012年1月在山东大学西校区动物实验中心完成。选用30只6周龄雌性SPF级Wistar大鼠,随机分为实验组和对照组,各15只。建立大鼠正畸牙移动模型,安装矫治器前3d实验组于腭侧黏骨膜下局部注射伊班膦酸钠50μL,对照组于相同部位注射生理盐水50μL,每3d注射1次直至实验结束。2组动物分别于安装矫治器后第3、7、14d各处死5只。检测大鼠第一磨牙近中移动距离、牙根吸收指数,并进行牙体牙周联合切片的组织学观察。结果安装矫治器后第7、14d时实验组牙齿移动距离、牙根吸收指数、破牙骨质细胞数及破骨细胞分化因子阳性表达均小于对照组,差异具有统计学意义(P<0.05)。结论局部应用伊班膦酸钠可抑制大鼠正畸牙齿的移动及牙骨质和牙本质的异常吸收,利于牙周组织受正畸力后的改建。     

伊班膦酸钠对正畸源性牙根吸收面积的影响

目的:通过牙齿移动距离的差异、牙周组织中破牙骨质细胞数量的变化及牙根吸收面积的差异,研究伊班膦酸钠对大鼠正畸源性牙根吸收的作用。方法:48只SPF级雌性Wistar大鼠,建立正畸牙齿移动动物模型,设置自身对照,对照侧为对侧未注药侧。在大鼠上颌双侧第一磨牙与上切牙之间安置一0.012英寸镍钛拉簧,施力60 g左右,所有大鼠均于安装矫治器前3 d在实验侧(大鼠上颌左侧)移动牙齿近中腭侧黏骨膜下局部注射50μL伊班膦酸钠,对照侧(大鼠上颌右侧)注射50μL 0.9%氯化钠液。每3 d注射一次直至实验结束。实验第3、7、14 d随机选择8只大鼠处死。分离大鼠头颅骨,用游标卡尺(精确度0.02 mm)测量上颌双侧第一磨牙移动的距离,并制备大鼠第一磨牙及其牙周组织切片,HE染色观察两侧牙周组织形态学变化,观察破牙骨质细胞的数量,采用图像处理软件对两侧的牙根吸收指数进行分析。结果:①牙齿移动距离随实验时间延长逐渐增加,组间比较:实验第3 d,实验侧和对照侧的牙齿移动距离平均值差异无统计学意义;实验第7 d和14 d,实验侧的牙齿移动距离均小于对照侧,差异具有统计学意义(P<0.05)。②实验侧第3 d、7 d和14 d大鼠第一磨牙牙周组织压力侧破牙骨质细胞数量均小于对照侧,且第7 d和14 d结果差异具有统计学意义(P<0.05)。③实验侧第3 d、7 d和14 d大鼠牙根吸收指数均小于对照侧,牙根吸收程度均比对照侧轻,且第7 d和14 d结果差异具有统计学意义(P<0.05)。结论:局部应用伊班膦酸钠可以减缓正畸牙齿移动的速度,减少牙周组织压力侧破牙骨质细胞的数量,减少正畸源性牙根吸收的发生。     

应用Micro-CT研究矫治力对正畸牙齿移动及牙根吸收的影响

目的：了解不同矫治力作用下大鼠牙齿移动距离及牙根吸收情况,探索应用Micro?CT研究正畸牙齿移动过程中矫治力对牙根吸收的影响。方法10周龄健康雄性SD大鼠64只（220~270 g）,分别施以10 g （10 g力组）、30 g力（130 g力组）拉右侧上颌第一磨牙向近中移动建立实验动物模型,以对侧同名牙为对照牙。于加力后第3、7、14、28天处死动物,使用Micro?CT扫描上颌第一磨牙及周围牙槽骨,测量上颌第一磨牙近中移动距离,计算加力28 d上颌第一磨牙近中根的表面凹陷体积,进行统计学分析。结果加力后发生牙齿移动,10 g力组在加力14 d内,牙齿移动量小于30 g力组（P =0.039）,在加力28 d时大于30 g力组（P<0.05）。加力28 d,10 g力组、30 g力组的牙根表面凹陷总体积高于对照组（P=0.004）,30 g力组产生的牙根表面凹陷总体积高于10 g力组（P<0.001）。结论 Micro?CT可以对牙齿移动及牙根吸收进行可靠评价及量化分析。加力后28 d,10 g力组移动量较30 g力组大,相应产生牙根吸收较30 g力组少。     

正畸治疗中牙根发育对牙根吸收影响的临床研究

目的探讨正畸治疗对正畸治疗前不同的牙根发育状况与正畸治疗中出现的牙根吸收的影响。方法120例经固定矫治青少年,检测其前磨牙、尖牙区的744颗牙齿正畸治疗前牙根发育状况及正畸治疗后牙根的等级。按正畸治疗前牙根是否发育完成分为发育完成组和发育未完成组两组。分析正畸治疗后牙根吸收情况。结果正畸治疗前牙根发育未完成的牙齿在正畸治疗中牙齿继续发育完成,牙根根管形态发育正常,无牙根吸收情况。正畸治疗前牙根发育完成的牙齿在正畸治疗后牙根出现不同比例的牙根吸收情况。两组之间有显著的组间差异(P<0.01)。结论 正畸治疗前牙根是否发育完成对正畸治疗中牙根是否出现吸收有显著的影响。     

Bio-oss骨胶原修复牙槽骨缺损区后对牙齿移动影响的临床初探

目的:评价应用Bio-oss骨胶原修复牙槽骨缺损区后对牙齿移动的影响。方法:对4例因多生牙拔除和2例因拔牙窝感染而造成牙齿移动区骨量不足病例。应用Bio-oss骨胶原修复6个月后,排齐整平牙列。观察牙齿在骨缺损修复区移动以及牙根吸收的情况。结果:6例骨缺损修复区愈合良好,牙槽嵴丰满,牙齿在骨缺损修复区移动的月平均距离为0.9mm,移动后6个月,12个月未见明显根吸收。结论:Bio-oss骨胶原吸收较缓慢,但未对牙齿的移动造成影响,可以考虑作为正畸临床骨缺损修复材料。     

ISO对大鼠正畸牙移动效果及牙周组织中Runx2、ODF水平的影响

建立SD大鼠正畸牙模型,随机分为对照组与ISO组,各20只,术后当天及7、14、21 d分别测定大鼠牙齿移动距离,HE染色观察牙周组织变化,对破骨细胞数量计数,检测Runt相关转录因子2(Runx2)和破骨细胞分化因子(ODF)水平.结果表明:加力后两组大鼠的牙齿均明显移动,且ISO组大鼠移动距离显著长于对照组(P＜0...     

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。     

Bone turnover rate in rats does not influence root resorption induced by orthodontic treatment

The aim of this study was to determine, in a rat model, whether a state of high or low bone turnover had an effect on the rate and type of tooth movement and on the incidence of root resorption induced by orthodontic treatment. The maxillary left first molar was moved mesially for 21 days in 52 6-month-old Wistar rats. They were divided into three groups: group 1 (n = 19) with normal bone turnover, group 2 (n = 16) with high bone turnover, and group 3 (n = 17) with low bone turnover. The contralateral side was left untreated to act as a control. The different metabolic rates were created by inducing hyper- and hypothyroidism. The amount of tooth movement was measured using an electronic calliper and the location of the centre of rotation (CRot) was determined after microcomputer tomographic scanning and subsequent three-dimensional reconstruction. Histomorphometric evaluation of root resorption was performed on undecalcified 7 microm thick sections of the maxilla and the differences between treated and untreated sides were evaluated. The results showed that high bone turnover increased the amount of tooth movement compared with the normal or low bone turnover state. There was no statistical difference in the location of the CRot. The treated side presented more root resorption than the untreated side, but this difference was not influenced by the metabolic rates. On the contrary, the untreated side in the low bone turnover group showed more root resorption, suggesting that in subjects where a decreased bone turnover rate is expected, the risk of root resorption could be increased.     

Tissue reaction to orthodontic tooth movement in acute and chronic corticosteroid treatment

Authors – Kalia S, Melsen B, Verna C Objectives – To study tissue reaction to orthodontic loading during the course of short‐ and long‐term corticosteroid administration. Design – ‘Split‐mouth’ design to perform orthodontic tooth movement in 64 six‐month‐old male rats divided into groups: no drug administration (n = 19), acute (n = 22) and chronic (n = 23) 8 mg/kg/day corticosteroid treatment. Performed in the Department of Orthodontics at Aarhus University. Experimental Variable – The upper left first molar was moved for 21 days. Bone markers were administered at 7 and 2 days before sacrifice. Histological sections were cut at the coronal level. Outcome Measure – Tooth movement rate, alveolar socket area, the relative extension of alveolar wall with erosion, and the mineralizing surfaces were measured and compared in the three groups. Results – Tooth movement rate increased in the chronic group. The mechanical load induced an enlargement of the alveolar wall that was less pronounced in both medicated groups. In the acute group the drug suppressed bone resorption and formation without mechanical stimulus. Force application resulted in significant increase in the relative extension of resorption and formation in both drug groups; it was particularly pronounced in the chronic group. Conclusion – Because acute corticosteroid ingestion reduces bone turnover, in these patients orthodontic treatment might best be postponed until a time the patient is free of the drug. Chronic steroid ingestion leads to an increased biological reaction to mechanical perturbation indicating that the orthodontic force level should be reduced and controlled more frequently in patients on chronic steroid treatment.     

The rate and the type of orthodontic tooth movement is influenced by bone turnover in a rat model

The influence of bone metabolism on both the rate and the type of orthodontic tooth movement was investigated. A rat model in which high (n = 16) and low (n = 17) bone turnover was pharmacologically induced was used. A non-pharmacologically treated group (n = 19) served as the control. A mesially directed constant single force of 25 cN was applied to the upper left first molar for a period of 3 weeks. The study was performed as a split-mouth design, the contralateral side of each animal serving as its control. The displacement of the molar crown was measured with an electronic calliper, while changes in inclination of the teeth were measured from micro-CT scans of the excised maxillae. The bone turnover significantly affected the rate of tooth movement. In the case of high turnover, the rate of tooth movement was increased while it was reduced in the case of low turnover. A controlled mesial tipping in all three groups was observed, but the actual location of the centre of rotation seemed to be influenced by the metabolic state of the bone. Based on the results it can be concluded that deviations in bone turnover influence the response to orthodontic forces, and should be taken into consideration when planning orthodontic treatment in patients with metabolic bone disease or those on chronic medication influencing bone metabolism.     

Tissue reaction to orthodontic tooth movement in different bone turnover conditions

Authors – Verna C, Melsen B Objectives – To study the tissue reaction to orthodontic load in normal, high, and low bone turnover states. Design – ‘Split mouth’ design performing orthodontic tooth movement in 52, 6‐month‐old male rats with: normal (n = 19), high (n = 16), and low bone turnover (n = 17), the latter two being obtained by induction of hyperthyroidism and hypothyroidism, respectively. Performed at the Department of Orthodontics at Aarhus University. Experimental Variable – The upper left first molar was moved for 21 days. Bone markers were administered 7 and 2 days before killing. Histological sections were cut at the coronal and apical levels. Outcome Measure – Alveolar socket area, periodontal ligament width, the relative extension of alveolar wall with erosion surfaces, and the mineralizing surfaces were measured and compared in the three groups. Results – Alveolar socket, periodontal ligament width, and erosion surface were larger on the treated than on the control side in the three groups. The normal and hypothyroid groups showed a wider periodontal ligament at the bucco‐distal site at the coronal level, while the hyperthyroid group showed a widening which was not spatially oriented. The normal and hyperthyroid groups showed higher erosion at the corono‐mesial site. The mineralizing surfaces were larger on the treated than on the control side in the normal and hypothyroid groups, but not in the hyperthyroid group. Conclusion – In the hyperthyroid group, the widening of the periodontal ligament was not spatially oriented and the increased erosion was not accompanied by increased formation, as observed in the normal and hypothyroid groups.     

Association between root resorption incident to orthodontic treatment and treatment factors

The purpose of this study was to clarify the prevalence and degree of root resorption induced by orthodontic treatment in association with treatment factors. The files of 243 patients (72 males and 171 females) aged 9-51 years were randomly selected from subjects treated with multi-bracket appliances. The severity of root resorption was classified into five categories on radiographs taken before and after treatment. The subjects were divided into extraction (n = 113 patients, 2805 teeth) and non-extraction (n = 130 patients, 3616 teeth) groups and surgical (n = 56 patients, 1503 teeth) and non-surgical treatment (n = 187 patients, 4918 teeth) groups. These subjects were also divided into two or three groups based on the duration of multiloop edgewise archwire (MEAW) treatment, elastic use, and total treatment time: 0 month (T1; n = 184 patients, 4831 teeth), range 1-6 months (T2; n = 37 patients, 994 teeth), more than 6 months (T3; n = 22 patients, 596 teeth); range 0-6 months (n = 114 patients, 3016 teeth) more than 6 months (n = 129 patients, 3405 teeth); range 1-30 months (n = 148 patients, 3913 teeth) and more than 30 months (n = 95 patients, 2508 teeth). The prevalence of overall and severe root resorption evaluated by the number of subjects and teeth was compared with a chi-square test. A Student's t-test for unpaired data was used to determine any statistically significant differences. The prevalence of severe root resorption based on the number of teeth was significantly higher in the group with extractions (P < 0.01). Longer use of a MEAW appliance and elastics also produced a significantly higher prevalence of root resorption (P < 0.05). On the other hand, the prevalence of severe root resorption was not significantly different between the subjects treated with or without surgery, but there was a significant increase when treatment time was prolonged (P < 0.05). A significant difference was found in the amount of root movement of the upper central incisors and the distance from their root apices to the cortical bone surface (P < 0.05). These are regarded as essential factors in the onset of root resorption. These results indicate that orthodontic treatment with extractions, long-term use of a MEAW appliance and elastics, treatment time, and distance of tooth movement are risk factors for severe root resorption.     

Experimental tooth movement through mature and immature bone regenerates after distraction osteogenesis in dogs.

The purpose of this study was to verify the influence of tooth movement on tooth roots and periodontal tissues when teeth were moved into mature, well-organized, and mineralized regenerate bone created after distraction osteogenesis compared with immature, fibrous, and less-mineralized bone. Six 15-month-old male beagles underwent 10 mm of bilateral mandibular distraction osteogenesis. After 2-week (group 1) and 12-week (group 2) consolidation periods, third premolars were moved distally into the regenerate bone with 100 g of orthodontic force for 12 weeks. Simultaneously, second premolars were also moved distally as controls. After completion of tooth movement, the experimental animals were killed, and their tissues were harvested for histological evaluation. When premolars in groups 1 and 2 were compared, group 1 showed higher rates of tooth movement until the eighth week of experimental tooth movement (P <.05). The amount of tooth movement was significantly greater in group 1 than in group 2 or in the control teeth (P <.05). In group 1, we observed considerable root resorption extending into the dentin, and the thickness of the dentin became approximately half that of the controls at the compression side adjacent to the distraction gap. This root resorption extended from the cementoenamel junction to the root apex. In group 2, root resorption on the compression side reached the dentin, but the root resorption was less than in group 1. These results indicated that heavy force and early orthodontic tooth movement are not recommended when teeth are moved through regenerated bone created by distraction osteogenesis, to avoid tipping and severe root resorption.     

Application of calcium phosphate ceramics to periodontal therapy. 8. Effects of orthodontic force on repaired bone with hydroxyapatite

It has been unclear whether M.T.M. is acceptable for patients treated with bone grafts using hydroxyapatite (HAP), which is not biodegradable. Therefore we studied histological changes in bone among HAP during orthodontic tooth movement. HAP was implanted into artificial bone defects adjacent to second premolars in beagle dogs, and as a control no material was implanted Three months after implantation, the second premolars were moved with orthodontic force. Then they were observed histopathologically. The results obtained were as follows. The amount of movement of the teeth in implanted sites was less than in the controls. In the pressure zone, resorption of bone by osteoclasts was observed in both the implanted and the control sites, in addition, root resorption occurred adjacent to HAP. Furthermore multinucleated giant cells were closely attached to HAP and were surrounded by bone and connective tissue. In retention period there was ankylosis between the roots and bone around HAP. In the tension zone, additional bone from HAP was observed. Bone defects were filled with bone in the implanted sites, but with connective tissue in the controls. These results suggest that bone among HAP was resolved by osteoclasts. Clinically, HAP implantation for the pressure zone should be avoided because of the occurrence of root resorption and ankylosis. But for the tension zone it seems to be effective because HAP implantation produces more repaired bone.     

Decreased alveolar bone turnover is related to the occurrence of root resorption during experimental tooth movement in dogs

Objective:To investigate the relationship between root resorption (RR) and bone turnover in two different types of tooth movement in dogs.Materials and Methods:A total of 16 dogs in two different groups were used. Tooth movement of dog premolars resulted from approximately 200 g of force. Histomorphometric analysis of premolar roots was assessed after 4 and 12 weeks of tooth movement by comparing nonresorptive to resorptive surfaces.Results:Histomorphometric analysis indicated a significant decrease in the bone formation rate in the root resorptive areas, which resulted in decreased bone volume after 12 weeks. The threshold to detect RR in periapical radiographs was about 1.0 mm².Conclusions:A sustained mechanical load, due to the prolonged stress and strain of continuous mechanics, induces elevated bone metabolic activity, such as the bone turnover (remodeling) and change in bone volume (modeling). Therefore, our data support the hypothesis that increased RR is related to decreased bone formation (turnover) in high stress areas exposed to prolonged orthodontic tooth movement.     

Non-steroidal and steroidal anti-inflammatory use in the context of orthodontic movement

The early phase of orthodontic tooth movement involves sterile acute inflammation of the periodontal ligament in response to biomechanical forces. Anti-inflammatories are pharmacologic agents used in medical and dentistry clinics. The aim of the study was to analyse the bone remodelling during orthodontic movement under non-steroidal and steroidal treatment. Male Wistar rats (n = 90) were randomly divided into three groups: C (control), non-steroidal anti-inflammatory drug (NSAID; potassium diclofenac), and steroidal anti-inflammatory drug (SAID; dexamethasone dissodium phosphate). The animals of the C group received 0.9 per cent saline solution, the NSAID group received potassium diclofenac CATAFLAM? (5 mg/kg), and the SAID group received dexamethasone dissodium phosphate DEXANIL? (2 mg/kg). Animals were sacrificed 3, 7, or 14 days after placement of the orthodontic appliance. The upper first molars were processed histologically; we quantified the blood vessels, Howship lacunae, and osteoclast-like cells present on the tension and compression sides of the periodontal ligament. Bone formation was evaluated under polarized light microscopy; 4.5 Image Pro-Plus? software calculated the percentage of immature/mature collagen present. The results showed that, in 3 and 7 days, NSAID and SAID groups presented fewer blood vessels, Howship lacunae, and osteoclast-like cells when compared to the control group. On the 7th and 14th days, there was a lower percentage of mature collagen in the SAID group (P < 0.001). These data demonstrate that potassium diclofenac and dexamethasone inhibit bone resorption during the initial period of orthodontic movement and that dexamethasone delays the collagen maturation process in established bone matrix.