Effect of sympathetic nervous activity on alveolar bone loss induced by occlusal hypofunction in rats

Objective

To elucidate the effect of sympathetic nervous activity on alveolar bone loss induced by occlusal hypofunction in rat molars.

Design

Occlusal hypofunction in the molar area was produced by attaching appliances to rat maxillary and mandibular incisors. In addition, a non-selective β-adrenergic receptor antagonist, propranolol, was administered orally to rats in drinking water to pharmacologically suppress sympathetic nervous activity. After 1 week, alveolar bones in all groups were examined by micro-CT, histomorphometry and histology to determine their trabecular bone phenotypes and histological changes.

Results

The marrow spaces of the interradicular alveolar bone of rat mandibular first molars (M1) increased in the occlusal hypofunction group (Group H) but not in the control group (Group C), whilst these decreased in rats in the occlusal hypofunction group that were administered propranolol (Group HB). Bone volume/tissue volume (BV/TV), trabecular thickness (Tb.Th) and trabecular number (Tb.N) for interradicular alveolar bone in M1 in Group H were significantly lower than those in Group C, whereas those in Group HB remained as high as those in Group C. The number of TRAP-positive cells in Group H increased compared to that in Group C, whereas it significantly decreased in Group HB.

Conclusions

These results suggest that sympathetic nervous activity may influence the alveolar bone loss induced by occlusal hypofunction.     

大鼠牙移动中牙周膜功能状态与牙槽骨改建关系的研究

目的:通过检测不同牙周膜功能状态大鼠磨牙移动过程中压力侧牙槽骨表面破骨细胞计数及牙移动距离的差异,探讨牙周膜功能状态与牙槽骨改建的关系.方法:选择48只6周龄体重(250±20)gSD大鼠,随机分为正常对照组(16只)和实验组(32只).通过拔除实验组大鼠右下颌所有磨牙使其上颌左、右第一磨牙咬合力改变,3周后分别形成牙周膜代偿性机能亢进模型和牙周膜废用性萎缩模型,据此实验组又分为萎缩组与亢进组(各16只).在各组大鼠上颌切牙和第一磨牙间放置5mm镍钛拉簧,初始力值60g,近中移动磨牙.分别于加力0d、3d、7d,每组各处死动物2只,14d处死其余动物,制备组织学标本,通过TRAP染色鉴别第一磨牙近中根压力侧牙槽骨表面破骨细胞并记数;对加力14d后的标本拍摄X线片测定牙齿移动距离.结果:牙周膜机能代偿性增强组牙齿移动距离(0.265±0.107mm)明显小于其它两组(0.631±0.142mm,0.679±0.090mm),P<0.01.牙周膜废用性萎缩组与正常对照组移动距离无显著性差异(P>0.05).萎缩组大鼠近中根压力侧牙槽骨表面破骨细胞计数在实验全过程中(除0d外)均低于亢进组和对照组,有显著性差异(P<0.05).结论:处于退化状态的废用性萎缩牙周膜对矫治力抵抗性差,细胞分化增殖不活跃,骨组织改建率低;机能代偿性增强牙周膜对矫治力抵抗性好,细胞分化增殖活跃,成骨活动大于破骨活动.     

Prevention of root resorption in hypofunctional teeth by occlusal function recovery

Objective:To clarify whether occlusal hypofunction is one of the key determinants for root resorption during tooth movement and root resorption is prevented by its recovery.Materials and Methods:The rats were randomly divided into one control and two experimental groups: hypofunctional and recovery groups. In the hypofunctional group, an anterior metal cap and bite plate were attached to the maxillary and mandibular incisors to simulate occlusal hypofunction. In the recovery group, the appliances were removed 7 weeks after their use, and the rats were allowed to bite for 4 weeks after removal. At the age of 16 weeks, the upper first molars were moved and after 0, 7, 14, and 21 days, the maxillae were resected. The resorption area was quantified morphohistologically and tartrate-resistant acid phosphatase (TRAP)-positive cells on the root surface were counted. We also examined the expressions of receptor activator of nuclear factor-κB ligand (RANKL), macrophage-colony stimulating factor (M-CSF), and interleukin (IL)-8 immunohistochemically.Results:The amount of root resorption and the number of TRAP-positive cells were significantly greater in the hypofunctional group than in the control and recovery groups. Moreover, immunoreactivity for RANKL, M-CSF, and IL-8 was detected in the periodontal ligament and on the root surface in the hypofunctional group.Conclusion:Occlusal hypofunction is one of the critical factors for root resorption; however, root resorption may be prevented by recovery of occlusal function. (Angle Orthod. 0000;0:1–8.)     

Micro-CT对骨皮质切开术中区域性加速现象的分析

目的:Micro-CT观测骨皮质切开辅助正畸治疗中牙齿移动速率和牙槽骨结构的改变。方法:选用75只4~6周龄的雄性SD大鼠,随机分为3组:组1:牙槽骨皮质切开辅助正畸(CO+TM),组2:传统正畸(TM),组3:单纯牙槽骨皮质切开(CO),按照时间点(加力4、7、14、21、28 d后)处死实验动物并进行Micro-CT扫描,测量牙移动距离;三维重建后测量牙颈部、根中部、根尖部3个平面张力侧及压力侧共6个区域的牙槽骨骨密度及骨体积。结果:1)牙移动距离:初期TM组高于CO+TM组,在第14、21、28天时,CO+TM组明显高于TM组(P<0.05)。速率:4~7 d时TM组大于CO+TM组,之后小于CO+TM组,组间比较P<0.05。2)骨密度:4、7、21、28 d时远中骨密度CO+TM组与CO、TM组比较持续下降,TM组则先下降后上升,CO组稳定于0左右(P<0.05)。3)骨体积:CO+TM组近中骨体积始终呈下降趋势,TM组近中骨体积自加力4 d后持续缓慢升高。结论:牙槽骨骨皮质改良切开术辅助正畸可以在术后14~28 d内增加正畸牙移动距离;牙槽骨远中侧骨密度降低明显,压力侧骨体积下降,张力侧骨体积上升,骨改建活跃,区域性加速现象在21 d时最明显。     

Effects of bone regeneration materials and tooth movement timing on canine experimental orthodontic treatment

Objectives:To evaluate the effects of bone regeneration materials and orthodontic tooth movement (OTM) timing on tooth movement through alveolar bone defects treated with guided bone regeneration (GBR) utilizing xenografts (Bio-Oss) and alloplast (β-TCP).Materials and Methods:Twenty-four standard alveolar bone defects in six male beagle dogs were treated by GBR using either Bio-Oss or β-TCP (experimental), whereas the control defects were left empty. The defects were further grouped into early or late subgroups, depending on OTM timing after GBR (ie 1 month or 2 months, respectively). Rates of OTM were measured intraorally, while computed tomography scan images were used to assess bone density, alveolar bone height, second premolar displacement, and tipping tendency.Results:Generally, the Bio-Oss early and Bio-Oss late subgroups recorded the lowest amount of tooth movement compared with other modes of GBRs assessed. Before OTM, the control group registered significantly lower bone height compared with the Bio-Oss and β-TCP groups (P < .01). The control group was inferior on bone density and bone height compared with Bio-Oss and β-TCP.Conclusions:The Bio-Oss group had favorable radiologic features (higher alveolar bone level and bone density with less premolar tipping) but showed slower OTM than the control group. The late OTM subgroup had favorable radiologic features and showed faster tooth movement than the early OTM in the β -TCP group.     

Bone apposition in surgical bony defects following orthodontic movement: a comparative histomorphometric study between root- and periodontal ligament-damaged and periodontally intact rat molars

BACKGROUND: The influence of orthodontic tooth movement with diminished periodontal support is unclear. The aim of the present study was to evaluate bone healing in surgical defects following orthodontic tooth movement with and without periodontal ligament (PDL) and root surface damage. METHODS: The study comprised 33 adult male Wistar rats, divided into two groups: group 1 (n = 14) with bony defect and no root damage and group 2 (n = 19) with periodontal bony defect including root/PDL damage on the mesial root of the maxillary first molar. One week after a surgical defect was created, orthodontic protraction of the right maxillary first molar was initiated in both groups. After 2 weeks of protraction, retention of 1 week was established; at the end of this period block sections were made. Histomorphometric analysis through light microscopy of decalcified tissue was performed. Results were statistically analyzed using independent samples t test and analysis of variance (ANOVA) with repeated measures. RESULTS: Differences between groups in total area of bone defect and bone apposition were not statistically significant. Bone apposition calculated as percentage of the bone defect was significantly (t-test) greater (P = 0.002) in group 2 (46.21%) than in group 1 (24.95%). Within each group, area of bone apposition was significantly (ANOVA) greater in the distal than in the mesial quadrants of the bony defect (P = 0.006) and in the apical than the occlusal ones (P = 0.021). CONCLUSION: Following orthodontic tooth movement, periodontal bony defects showed enhanced bony healing compared with alveolar bone defects with no direct association with the periodontal attachment apparatus.     

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.     

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目的探讨淫羊藿总黄酮（TFE）对正畸大鼠牙齿移动及压力侧牙周组织的影响。方法本研究于2012年9月至2013年4月在山西医科大学口腔医院进行。选取8周龄雄性Wistar大鼠40只,建立正畸牙移动模型。按随机数字表法分为对照组（A组）和实验组（B、c、D组）,每组10只。从正畸加力第1天开始,A、B、c、D组分别灌服不同剂量TFE（依次为0、75、150、300mg／kg）,每天1次,第10天处死全部大鼠。测量大鼠左上第一磨牙移动距离,HE染色观察其压力侧牙周组织变化。结果A、B组牙齿移动距离差异无统计学意义（P〉O．05）;C、D组牙齿移动距离均明显小于A组（对照组）,差异有统计学意义（均P〈0．05）。HE染色显示,实验组正畸牙齿压力侧骨吸收陷窝少于对照组。结论’FFE可抑制正畸大鼠牙齿移动及压力侧牙槽骨吸收,且在一定范围内,剂量越大作用越明显。     

Influence of occlusal hypofunction on the elastic property and bone formation of rat alveolar bone

The purpose of this study was to investigate the influence of occlusal hypofunction on the maintenance of the elastic property and alveolar bone formation using an occlusal hypofunction model. Analyses of the elastic property and bone formation of the alveolar bone were carried out by the compression test and the bone histomorphometry in the two directions (the tooth axis direction and the bucco-lingual direction). The compression test was done with the texturometer to analyse the springiness of bone specimens of the mandibular first molar. Bone histomorphometric analyses were evaluated using double labeled frontal section. Results showed that occlusal hypofunction significantly reduced the springiness and suppressed the alveolar bone formation in the bucco-lingual direction. These results suggested that occlusal function plays an important role in maintenance of the elastic property and bone formation of the alveolar bone.     

Comparative study of gene expression during tooth eruption and orthodontic tooth movement in mice

Objective:  The aim of this study was to understand tooth eruption by comparing the gene expression during tooth eruption and orthodontic tooth movement (OTM).
Materials and methods:  Orthodontic force was applied on maxillary molars for 2, 4, 7 and 14 days to study tooth movement. Mice at PN 0, 7, 10, 15 and 21 were fixed to observe tooth eruption. Comparative study of two procedures was assessed by haematoxylin and eosin, tartrate-resistant acid phosphatase staining and in situ hybridization for matrix metalloproteinase ( Mmp ) 2 , 13 , bone sialoprotein ( Bsp ) and osteocalcin ( Ocn ).
Results:  Tartrate-resistant acid phosphatase activity and expression of Mmp2 , 13 were obviously detectable in the compression region during OTM. They were also identified in the occlusal and apical region of alveolar bone during tooth eruption. Strong expression of Bsp and Ocn was detectable at the tension side during OTM. These genes were also expressed in the inner lateral region of alveolar bone adjacent to the tooth, but absent in the inner surface of the occlusal and root apical regions during tooth eruption.
Conclusion:  The process of alveolar bone metabolism during developmental eruption and OTM shares the same mechanism. Internal force, as the orthodontic force for OTM, may be initiating factor for tooth eruption.     

Effects of long-term occlusal hypofunction and its recovery on the morphogenesis of molar roots and the periodontium in rats

Objectives:To investigate the effects of long-term, artificially created, hypofunctional occlusion and its recovery on the morphology of rat molar roots.Material and Methods:Eighteen 5-week-old Wistar-strain male rats were randomly divided according to their periodontal conditions into normal, hypofunctional, and recovery groups (n  =  6 in each). In the experimental hypofunctional and recovery groups, a bite-raising appliance was set to produce hypofunction at the molar region. All groups were analyzed at 16 weeks of age using three-dimensional micro-computed tomography. Root length, width, and area as well as the thickness and the area of the periodontal ligament (PDL) space of the maxillary first molar were calculated.Results:Roots were longer and narrower in the hypofunctional group than in the control group. The mesial root in particular showed a dramatic change. Root area also decreased significantly in the hypofunctional group compared to the other groups. Moreover, the PDL thickness and area decreased significantly in the hypofunctional group compared to the control group, but increased in the recovery group compared to the hypofunctional group.Conclusions:These findings suggest that root size and PDL structure may be reduced due to disuse atrophy resulting from a defect in occlusal function, but may be recovered following a gain of occlusal stimuli.     

Facilitation of experimental tooth movement by NOC-18, a long-acting nitric oxide donor

PurposeIn orthodontic tooth movement, osteoclasts play a crucial role in bone resorption on the compression side of the alveolar bone. It has been reported that nitric oxide is involved in bone remodeling caused by mechanical loading, and we previously reported that NOC-18, a long-acting nitric oxide donor, augmented RANKL-induced osteoclast differentiation in mouse monocytic RAW264 cells as well as mouse bone marrow macrophages. In this study, we investigated whether NOC-18 facilitated experimental tooth movement in mice.Materials and methodsEight-week-old male ddY mice were used. Experimental tooth movement was induced by the insertion of an orthodontic elastic between the left maxillary first molar and second molar. Just after the insertion of the elastic, NOC-18 was intraperitoneally administered once, and mice were killed after 3 days. For the detection of osteoclasts, HE staining, TRAP staining, and immunostaining for cathepsin K were performed.ResultsAn intraperitoneal injection of NOC-18 significantly increased the distance of experimental tooth movement. Furthermore, the number and area of osteoclasts on the compression side of the alveolar bone surface was significantly higher in the NOC-18 group.ConclusionThese results suggested that systemic administration of NOC-18 might have some effect to facilitate experimental tooth movement in mice via the augmentation of osteoclast differentiation on the compression side of the alveolar bone.     

Comparison of the effects of three surgical techniques on the rate of orthodontic tooth movement in a rat model

Objective:To evaluate the effect of corticotomy and corticision, with and without a full mucoperiosteal flap, on the rate of tooth movement and alveolar response in a rat model.Materials and Methods:Sixty male, 6-week-old Wistar rats were divided into five groups based on surgical procedure, as follows: control (no tooth movement), orthodontic tooth movement (OTM) only, corticotomy, corticision, and corticision with full mucoperiosteal flap (corticision + flap). A force of 10–15g was applied from the maxillary left first molar to the maxillary incisors using nickel-titanium springs. Surgery was performed at the time of appliance placement (day 0), and tooth movement occurred for 21 days. Micro–computed tomography was performed on day 21 to evaluate the amount of tooth movement and alveolar bone parameters. Histomorphometry, including tartrate-resistant acid phosphatase staining, was performed to quantify the osteoclast parameters at day 21.Results:No statistical differences in the amount of OTM, bone volume fraction, and tissue density and the osteoclast parameters were found among all experimental groups.Conclusions:Corticotomy and corticision, with or without a full mucoperiosteal flap, did not show a significant effect on either the OTM magnitude or alveolar bone response.     

正畸牙移动困难相关因素研究进展

正畸牙移动是以牙周组织塑建为生物学基础的复杂生理过程。许多因素如口颌复合体的解剖特征、咬合干扰、机械因素及系统性因素等都可能对其造成影响,导致正畸牙移动困难。近年来,国内外学者非常关注牙移动困难相关因素的研究,但当前有关正畸牙移动困难的研究多为动物实验及回顾性研究,亟需高质量的临床试验及循证医学研究。许多正畸牙移动困难相关因素的作用机制尚存在争议,未形成一个普遍认可的完善理论体系,目前认为牙槽骨缺损、上颌窦、牙龈、牙根粘连、骨岛和摩擦力等因素都可能导致正畸牙移动困难。了解正畸牙移动困难的相关因素有助于正畸医生为患者制定更全面的个性化治疗方案,实现更高效、安全的牙移动。本文对目前正畸牙移动困难的相关因素作一综述,为正畸临床治疗提供参考。     

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。     

Treatment of ankylosed maxillary central incisors by single-tooth dento-osseous osteotomy and alveolar bone distraction

When tooth ankylosis occurs in growing children, the ankylosed tooth fails to erupt and gradually positions itself below the occlusal plane. This causes functional and esthetic problems, and orthodontic treatment is often impossible. To clarify this problem, we developed a new treatment protocol for the movement of ankylosed teeth. This consists of single-tooth dento-osseous osteotomy and alveolar bone distraction using orthodontic multibracket appliances. A special distraction device is not required, thus reducing the burden to patients. Two cases in which an ankylosed maxillary central incisor was successfully treated with this protocol are presented.     

Segmental alveolar distraction for the correction of unilateral open-bite caused by multiple ankylosed teeth: A case report

Abstract

Ankylosed teeth fail to erupt to meet their counterparts in the opposite jaw. In cases where ankylosis occurs in multiple teeth, the occlusion shows an open bite. This article describes a case of unilateral open bite caused by multiple ankylosed teeth, where treatment involved segmental alveolar bone distraction. A 25-year-old female patient presented with a left-sided unilateral open bite. On the left-hand side, only the lower incisors were not ankylosed. On the right, the maxillary first molar was ankylosed. All these ankylosed teeth were positioned below the occlusal plane. Her mother and brother also had multiple ankylosed teeth, and a familial cause was considered. Orthodontic tooth movement was considered impossible and segmental osteotomy on the left maxillary alveolar bone and downward bone distraction were performed as an alternative. A distractor consisting of orthodontic bands, wires and screws was devised and worn in the left mandibular dentition. Multi-bracket orthodontic appliances were also used for distraction. The amount of vertical movement was 7 mm at the premolar region. Five months after distraction, the multibracket appliance was removed, and fixed and removable retainers were placed. Eight months after distraction, prosthodontic restorations on the occlusal surfaces of the ankylosed teeth were made to obtain the final occlusion. The unilateral open bite was successfully treated and a good occlusion was obtained. The occlusion has shown good long-term stability for more than 3 years.     

丹参联合电动牙刷对大鼠正畸牙移动过程的影响

目的：研究中药丹参联合电动牙刷对大鼠正畸牙齿移动及移动过程中牙槽骨密度的影响。方法：选取72只SD雄性大鼠,建立大鼠正畸牙齿移动实验模型,随机分为丹参联合电动牙刷+加力组（A组）丹参+加力组（B组）和对照组单纯加力组（C组）,每组24只。 A组每天于左上第一磨牙颊黏膜处注射丹参,并间歇进行15 min电动牙刷颤动,B组注射丹参,C组为对照组。3组动物于正畸加力1、3、7、14 d分批次处死,每批处死6只,分离大鼠上颌骨,HE染色观察牙周组织变化并测量牙齿移动的距离及牙槽骨骨密度。使用SPSS 19.0软件进行数据分析。结果：A组和B组较C组的牙周组织中更早更多出现破骨细胞;A、B组除第1 d外牙齿移动距离均明显高于C组（P<0.01）,且A组明显高于B组（P<0.01）;第7d,A组牙槽骨密度明显高于C组（P<0.05）,第14 d,A组明显高于B组（P<0.05）,且A、B组均高于C组（P<0.05）,差异有统计学意义。结论：丹参联合电动牙刷在加速牙齿移动的同时能有效地降低牙槽骨骨密度的减少。     

Orthodontic tooth movement enhances bone healing of surgical bony defects in rats

BACKGROUND: The question of whether the repair of an alveolar bony defect can be enhanced by orthodontic tooth movement was addressed. METHODS: Alveolar bone defects were created in 52 Wistar male rats anterior to both maxillary first molars. After 1 week of healing, orthodontic protraction was applied for 2 weeks on the right side, resulting in mesial tipping and displacement movement. Subsequently, a retention appliance was inserted for 1 week. The left side served as the untreated (control) group. Vital bone staining (procion brilliant red H-8) was administered before and after orthodontic traction. Histomorphometric analysis was performed on 62 hemimaxillae using UV confocal microscopy and an imaging program. The total area of the bony defect was divided into 4 equal quadrants, and the area of bony apposition in each quadrant was measured. RESULTS: The total area of bony apposition was 6.5-fold larger in the treated (26.41 x 10(4) +/- 28.92 x 10(4) microm2) than in the control group (4.07 x 10(4) +/- 2.82 x 10(4) microm2), approaching statistical significance (P = 0.065). The treated occlusal quadrants demonstrated highly significant (P= 0.010), greater bone apposition compared to the control group (13.8-fold) and to the treated apical quadrants (P= 0.04, 5-fold). CONCLUSIONS: This study confirms that orthodontic tooth movement is a stimulating factor of bone apposition. A conversion in the repair pattern of the bony defect from apicoocclusal in the control group (no tooth movement) to occlusoapical in the treated group (with tooth movement) further supports the linkage between tooth movement and enhanced bone deposition. Clinical implication suggests incorporation of orthodontic tooth movement in regenerative therapy.