Growth hormone receptor and IGF-I receptor immunoreactivity during orthodontic tooth movement in the prednisolone-treated rat.

Bone remodeling during tooth movement is regulated by local and systemic factors. Two regulators of bone metabolism are growth hormone (GH) and insulin-like growth factor-I (IGF-I). Their effects are mediated via binding to GH receptor (GHR) and IGF-I receptor (IGF-IR) in target tissues. Corticosteroids may affect the activity of these growth factors. This study examined the effect of prednisolone on GHR and IGF-IR expression in dental tissues following orthodontic tooth movement. The corticosteroid-treated group (N = 6) was administered prednisolone (1 mg/kg) daily and the control group (N = 6) received equivalent volumes of saline. An orthodontic force (30 g) was applied to the maxillary first molar. Animals were sacrificed 12 days postappliance insertion. Sagittal sections of the first molar were stained for GHR and IGF-IR immunoreactivity. GHR and IGF-IR cell counts were elevated following appliance-treatment. Orthodontic tooth movement appeared to up-regulate GHR and IGF-IR immunoreactivity, but this up-regulation was reduced following prednisolone treatment. The suppression of GHR and IGF-I immunoreactivity in steroid-treated animals infers the mechanism whereby bone resorption and deposition, necessary for orthodontic tooth movement, may be inhibited by prednisolone. However, at 12 days postappliance insertion, no difference in orthodontic tooth movement was observed following low-dose prednisolone treatment.     

Periodontal healing following orthodontic movement of rat molars with intact versus damaged periodontia towards a bony defect

The aim of this research was to determine whether orthodontic tooth movement influences periodontal healing. In 16 male Wistar rats, 12 week of age, a bony defect was created mesial to both maxillary first molars, not including the attachment apparatus (group 1), and in 15 animals, the defect included the periodontal ligament (group 2). In both groups, the right first molar was moved mesially (orthodontic side) for 2 weeks followed by a 1-week retention period; the contralateral molar was not moved (control side). Histomorphometric analysis was performed. The results within and between the different treatment groups and sides were statistically compared by t-test and analysis of variance with repeated measures on logarithmic transformation. Junctional epithelium was significantly larger at the control than at the orthodontic side of both groups (P = 0.024), and significantly larger in group 2 than in group 1 (P < 0.001). A significantly (P = 0.034) larger pocket depth was found at the control side in group 1. Supracrestal connective tissue was larger at the control than at the orthodontic side for both groups and significantly larger in group 2 than in group 1 (P = 0.004). Root resorption was found infrequently only at the orthodontic side in both groups (five out of 31 cases). The principal findings suggest favourable effects of orthodontic tooth movement on restraining epithelial apical down-growth and decreasing pocket depth. Orthodontic treatment could not completely avoid formation of a long epithelial attachment. Therefore, periodontal regenerative surgery might be indicated prior to orthodontic tooth movement. Orthodontic movement, shortly after periodontal surgery, had no detrimental effect on periodontal soft tissue healing or on diminished but non-inflamed periodontal tissues.     

牙周膜牵张成骨快速移动牙齿的组织学观察

目的 观察牙周膜牵张成骨快速移动牙齿的牙周组织学变化。方法 将6只杂种犬随机分为2w，4w，6w三组（每组二只）。拔除两侧第二前磨牙，并随机选择其中一侧为实验侧，另一侧为常规橡皮圈加力方法对照侧。动物基牙预备：拔牙凿骨减阻；粘结自制牵张装置；实验组以2次／天的频率、0．15fnm／次的速率加力，2w后固定保持。对照组以传统橡皮链对移动牙施加100g力值，加力2w后，固定保持。测量支抗牙、移动牙移动距离：分别于第2、4、6w各宰杀二只动物，观察实验侧与对照侧的组织学变化。结果 ①实验侧移动牙加力2w平均向远中移动3．78mm，对照侧移动牙平均向远中移动1．09mm（P〈0．01），实验侧支抗牙平均向近中移动0．42mm，对照侧支抗牙平均向近中移动0．40mm（P〉0．01）。②组织学观察得出：2w组，实验侧与对照侧相比，实验侧牙周膜显著增宽，牙周膜内成纤维细胞增殖，新生板层状牙槽骨明显增多，与牵张作用力方向一致；4w组，旧间隔骨已改建完成，牙周膜宽度基本恢复正常；6如组两种方法作用下移动牙牙周组织己无明显差异。结论 牙周膜牵张成骨可以快速移动牙齿；牙周组织不会出现不可复性损害。     

正畸牙移动过程中高迁移率族蛋白B1的改变

目的:研究高迁移率族蛋白B1(High Mobility Group Box-1,HMGB1)在正畸牙移动过程中的表达,以指导正畸临床加力。方法:30只Wistar大鼠,分为0、1、3、5和7 d组,每组6只;左侧施加0.6 N以近中移动上颌第一磨牙,右侧放置正畸装置但不加力作为对照;HE染色观察正畸牙移动过程中牙周组织的变化,免疫组织化学染色观察牙周支持组织中HMGB1的变化,以平均光密度法检测组织中HMGB1的表达量。结果:HE染色显示,加力1 d~7 d,大鼠第一磨牙牙周组织呈现正畸牙移动的典型变化:压力侧牙周膜变窄,呈现纤维排列紊乱,破骨细胞数目逐渐增多;张力侧牙周膜增宽,纤维排列整齐,成骨细胞数目逐渐增多。免疫组织化学染色显示,压力侧1 d时HMGB1表达量最低(0.0012 ± 0.0009),显著低于1 d对照组(0.0239 ± 0.011),从1~7 d,压力侧HMGB1逐渐增加,到7 d时到达加力后最高值(0.0127 ± 0.0014);张力侧1 d时HMGB1表达量(0.0193 ± 0.0012)低于1 d对照组(0.0284 ± 0.009),到5 d时,张力侧HMGB1达到最高值(0.0324 ± 0.0014),但与5 d对照组(0.0289 ± 0.0012)无显著差别。结论:过大的正畸矫治力减少压力侧牙周组织内HMGB1的表达,减慢透明样组织清除和正畸牙移动。     

机械敏感离子通道Piezo1在糖尿病大鼠牙移动过程中的表达和功能研究

目的 研究糖尿病大鼠正畸牙齿移动中张力侧牙周组织内Piezo1的表达变化, 探索其在张力侧牙周组织改建中的作用。方法 选取60只健康雄性Wistar大鼠为研究对象,分成对照组以及糖尿病组,以双侧切牙为支抗施加40 g拉伸力近中移动左侧第一磨牙,分别在0、7、14 d处死大鼠后获得左上后牙区牙槽骨块。HE染色检测组织形态变化,免疫组化及荧光染色检测张力侧Piezo1、Osterix以及Runx2的表达水平,Micro-CT检测张力侧骨组织相关参数指标。结果 正畸牙移动激活了张力侧牙周膜中Piezo1的表达,糖尿病大鼠Piezo1以及成骨分化关键转录因子Osterix和Runx2的表达显著低于健康大鼠。结论 糖尿病显著抑制了正畸牙移动过程中张力侧牙周膜中Piezo1的表达,降低了张力侧成骨活性,抑制正畸牙移动张力侧牙周组织的改建。     

Effect of a static magnetic field on orthodontic tooth movement in the rat

Orthodontic tooth movement may be enhanced by the application of a magnetic field. Bone remodelling necessary for orthodontic tooth movement involves clastic cells, which are tartrate-resistant acid phosphatase (TRAP) positive and which may also be regulated by growth hormone (GH) via its receptor (GHR). The aim of this study was to determine the effect of a static magnetic field (SMF) on orthodontic tooth movement in the rat. Thirty-two male Wistar rats, 9 weeks old, were fitted with an orthodontic appliance directing a mesial force of 30 g on the left maxillary first molar. The appliance incorporated a weight (NM) or a magnet (M). The animals were killed at 1, 3, 7, or 14 days post-appliance insertion, and the maxillae processed to paraffin. Sagittal sections of the first molar were stained with haematoxylin and eosin (H&E), for TRAP activity or immunohistochemically for GHR. The percentage body weight loss/gain, magnetic flux density, tooth movement, width of the periodontal ligament (PDL), length of root resorption lacunae, and hyalinized zone were measured. TRAP and GHR-positive cells along the alveolar bone, root surface, and in the PDL space were counted. The incorporation of a SMF (100-170 Gauss) into an orthodontic appliance did not enhance tooth movement, nor greatly alter the histological appearance of the PDL during tooth movement. However significantly greater root resorption (P = 0.016), increased width of the PDL (P = 0.017) and greater TRAP activity (P = 0.001) were observed for group M at day 7 on the compression side. At day 14 no differences were observed between the appliance groups.     

Tooth movement and changes in periodontal tissue in response to orthodontic force in rats vary depending on the time of day the force is applied.

The purpose of this study was to investigate whether there are any differences in tooth movement or in the response of periodontal tissue to orthodontic force when the force is applied at different times of the day. One hundred 6-week-old male Wistar rats were divided into one control group without force application and three experimental groups based on the time of day the force was applied to the upper first molars. Animals in the whole-day group received force continuously throughout the experimental period, while animals in the light- and dark-period groups received force only during the light (07:00-19:00) or dark period (19:00-07:00), respectively. Tooth movement was measured using the occlusal view of a precise plaster model with a profile projector. Periodontal tissues were evaluated histologically. The time course of tooth movement varied among the groups. Tooth movement over 21 days in the whole-day and light-period groups was about twice that as in the dark-period group. The formation of new bone on the tension side in the whole-day and light-period groups was more than twice that as in the dark-period group. On the pressure side, more osteoclasts appeared on the alveolar bone in the whole-day and light-period groups than in the dark-period group. The light-period group showed less extensive hyalinization of the periodontal ligament (PDL) than the whole-day group. The area of root resorption on day 21 also varied among the groups. Interference by masticatory forces did not seem to be a principal cause of the decreased tooth movement in the dark-period group. These results indicate that there are considerable variations in tooth movement and in the response of periodontal tissue to orthodontic force when the force is applied at different times of the day in rats. The results suggest that diurnal rhythms in bone metabolism have important implications in orthodontic treatment.     

不同浓度木通皂苷D对大鼠正畸牙移动的影响

目的:探讨局部注射不同浓度的木通皂苷D对大鼠正畸牙移动的影响。方法:40只6周龄雌性Wistar大鼠,随机分为4组,建立正畸牙移动动物模型。以上颌两中切牙为支抗,牵引上颌第一磨牙向近中移动,镍钛拉簧加力40 g。ASD1组以5 mg/kg的剂量局部注射ASD溶液;ASD2组以10 mg/kg的剂量局部注射ASD溶液;PGE2组以25 μg/kg的剂量局部注射PGE2溶液;空白对照组注射生理盐水。4组动物分别于正畸加力3、7、14、21、28 d后分批处死,测量各期上颌第一磨牙的移动距离,H-E染色观察切片牙周组织及破骨细胞数量的变化,采用SPSS13.0软件包对数据进行统计学分析。结果:各实验组动物牙移动距离均大于对照组,加力第3天,只有PGE2组与对照组相比有显著差异（P<0.05）。加力第7天,ASD2组和PGE2组与对照组相比均有显著差异（P<0.05）。加力第14、21、28天,ASD1组、ASD2组和PGE2组与对照组相比均具有统计学意义（P<0.05）。各时间段ASD2组和PGE2组之间牙移动距离相比无统计学意义（P>0.05）。组织学观察,压力侧多核破骨细胞数目随时间推移呈上升趋势,第21天达到高峰,随后逐渐减少。结论:局部注射ASD可促进大鼠正畸牙移动,ASD以10 mg/kg的剂量局部注射,其作用与PGE2促进正畸牙移动的效果相似,较5 mg/kg剂量的ASD促进牙移动的效果明显。     

局部注射重组人转化生长因子对大鼠正畸牙移动的影响

目的:探讨局部注射重组人转化生长因子 (rhTGF -β1)对大鼠正畸牙移动速度的影响。方法:80只模型大鼠随机分为实验组和对照组,每组又按1、4、7、10和14 d再分为5个小组,每小组8只。实验组从加力的第1天开始,每2 d在大鼠加力侧上颌第一磨牙颊侧黏膜下注射rhTGF-β1 0.1 mL(5 ng/mL),对照组注射相同容量的PBS。加力后依实验设计时间分别处死每1小组大鼠。体视显微镜观察并采集图像,运用计算机图像分析软件测量牙移动的距离,同时应用TRAP组织化学染色观察不同时段压力侧破骨细胞数量的变化,采用SPSS 17.0 软件包对数据进行统计学分析。结果:局部注射rhTGF-β1的牙移动速度较对照组快,在加力后第7天,牙移动距离差异显著(P<0.05);第10天和第14天相比,差异显著(P<0.01)。实验组压力侧破骨细胞的TRAP阳性细胞数较对照组显著增多(P<0.01)。结论:局部注射rhTGF-β1增强了大鼠正畸牙破骨细胞的活性,促进了破骨细胞的骨吸收功能,加速了正畸牙移动。     

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。     

Clinical effect of CO(2) laser in reducing pain in orthodontics

OBJECTIVE: To test the hypothesis that there is no difference in the pain associated with orthodontic force application after the application of local CO(2) laser irradiation to the teeth involved. MATERIALS AND METHODS: Separation modules were placed at the distal contacts of the maxillary first molars in 90 patients in this single-blinded study. In 60 of these patients (42 females and 18 males; mean age = 19.22 years) this was immediately followed by laser therapy. The other 30 patients (18 females and 12 males; mean age = 18.8 years) did not receive active laser irradiation. Patients were then instructed to rate their levels of pain on a visual analog scale over time, and the amount of tooth movement was analyzed. RESULTS: Significant pain reductions were observed with laser treatment from immediately after insertion of separators through day 4, but no differences from the nonirradiated control side were noted thereafter. No significant difference was noted in the amount of tooth movement between the irradiated and nonirradiated group. CONCLUSIONS: The hypothesis was rejected. The results suggest that local CO(2) laser irradiation will reduce pain associated with orthodontic force application without interfering with the tooth movement.     

局部注射阿仑膦酸钠对大鼠正畸牙移动的影响

目的观察局部注射阿仑膦酸钠对大鼠正畸牙移动及牙周组织的影响。方法32只Wistar大鼠分为对照组和低剂量、中剂量、高剂量三个实验组,使用40g力牵其左侧上颌第一磨牙近中移动,实验中分别将生理盐水、0.02mmol/L、0.1mmol/L、0.5mmol/L的阿仑膦酸钠溶液注射入各组大鼠上颌第一磨牙近中腭侧的粘骨膜下,注射于实验前3d开始,每3天一次,每次50μl。分别在0、1、3、7、14、17、21d时取模法测量大鼠牙移动量。第21天取上颌组织块经固定、脱钙、脱水、包埋后切片,HE染色观察牙周组织变化,TRAP染色观察压力区破骨细胞数、破牙骨质细胞数,比较各组间是否有差异。结果①各实验组大鼠第一磨牙移动距离显著低于对照组,并随药物浓度增高其抑制效果增强。②实验组压力区破骨细胞数和破牙骨质细胞数显著低于对照组。结论局部注射不同浓度阿仑膦酸钠能获得不同的抑制牙齿移动的效果,可应用于临床中作为一种增强支抗的手段。     

牙周炎正畸牙周组织中胰岛素样生长因子-Ⅰ表达的实验研究

目的观察胰岛素样生长因子-I在牙周炎正畸牙移动过程中的表达,探讨其对炎性正畸牙周组织的影响。方法 36只wistar大鼠建立牙周炎动物模型,并随机平分为牙移动1天、3天、7天、14天、21天组及对照组,近中移动各实验组大鼠上颌第一磨牙,处死后制取牙周组织标本,行HE染色和免疫组化分析。结果在既定时间内,IGF-Ⅰ在压力侧和张力侧均有阳性表达,在加力第3天两侧表达均达到峰值,但强度较弱。结论 IGF-Ⅰ在正畸牙周组织改建中,参与了炎症正畸牙周组织改建过程,影响张力侧的成骨活动和压力侧的破骨活动。     

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.     

Evening primrose oil effects on osteoclasts during tooth movement

This study was conducted to investigate the influence of supplemented evening primrose oil (EPO) on osteoclast expression during experimental tooth movement in rats. Forty-eight 10-week-old male Sprague-Dawley rats were divided into experimental and control groups. Animals in the experiment group were fed a 7.25 g/kg daily dose of EPO orally by gastric intubation for 20 days before orthodontic tooth movement. The animals in the control group received an equivalent volume of distilled water by the same method. On day 21, a 40-g mesial tipping force was applied to the maxillary right first molar of each rat. After loading, six animals in each group were sacrificed on days 0, 3, 7, and 14 with the appliance in situ. On day 3, the number of osteoclasts on the appliance side of the experimental group was significantly increased compared with the control group (P < .05). On day 7, the number of osteoclasts on the non-appliance side of the experimental group was significantly increased compared with the control group (P < .05). This study indicates that oral administration of EPO can increase the number of osteoclasts and may accelerate orthodontic tooth movement.     

����޽�ܻ�ͪ���������������ƶ���ѹ����������֯Ӱ���о�

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。     

Local and chronic application of PTH accelerates tooth movement in rats

We previously reported that whereas systemic continuous infusion of parathyroid hormone (PTH) accelerated orthodontic tooth movement, systemic but intermittent injection of PTH did not increase the rate of tooth movement. Analysis of these data suggested that continuous administration of PTH could be applicable for orthodontic therapy. In the present study, we investigated whether local and chronic application of PTH(1-34) would accelerate orthodontic tooth movement. To increase the residence time of PTH in the injected area, we used methylcellulose (MC) gel (2% W/V) for a slow-release formulation of PTH. MC gel containing PTH (PTH-MC) continuously released biologically active PTH into the acceptor medium for more than 72 hrs in vitro. When male rats received a local injection of PTH-MC into the subperiosteum in the mesio-palatal region of the maxillary first molar (M1) every other day, M1 movement, which was mesially drawn by an orthodontic coil spring attached to the maxillary incisors, was accelerated in a dose-dependent manner. PTH-MC injection at 1 microg/400 g body weight caused a 1.6-fold increase in the rate of tooth movement. The acceleration of tooth movement by PTH-MC injection was marked on days 6, 9, and 12. Local injection of PTH dissolved in saline without MC did not significantly accelerate tooth movement on day 6 or later. Histological examination revealed active osteoclastic bone resorption and a widened periodontal space on the compression side of the periodontal tissue in the PTH-MC-injected rats. These results suggest that local injection of PTH in a slow-release formulation is applicable to orthodontic therapy.     

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.     

Histological response in dental pulp of accelerate tooth movement using periodontal ligament distraction osteogenesis in dogs

Purpose

This study compared initial histological change in dental pulp in response to periodontal ligament distraction osteogenesis (PLDO) with that to conventional orthodontic treatment to determine the effectiveness of PLDO.

Comparison of the effects of 1,25 dihydroxycholecalciferol and prostaglandin E2 on orthodontic tooth movement.

This study compared the effects of local administrations of prostaglandin E2 (PGE2) and 1,25-dihydroxycholecalciferol (1,25-DHCC) on orthodontic tooth movement in rats. Thirty-seven 6-week-old male Sprague-Dawley rats, weighing 160 +/- 10 g were used. Five rats served as the baseline control group. A fixed appliance system exerting 20 g of distally directed force was applied on the maxillary incisors of 32 animals for 9 days. Eight rats served as the appliance control group; 8 received a 20-microL injection of dimethyl sulfoxide (solvent for 1,25-DHCC) on days 0, 3, and 6; 8 received 20 microL of 10(-10) mol/L 1,25-DHCC on days 0, 3, and 6; 8 received a single injection of 0.1 mL of 0.1 microg PGE2 only on day 0. There was no significant difference in tooth movement between the PGE2 and the 1,25-DHCC groups. Both PGE2 and 1,25-DHCC enhanced the amount of tooth movement significantly when compared with the control group. The numbers of Howship's lacunae and capillaries on the pressure side were significantly greater in the PGE2 group than in the 1,25-DHCC group. On the other hand, the number of osteoblasts on the external surface of the alveolar bone on the pressure side was significantly greater in the 1,25-DHCC group than in the PGE2 group. Thus, 1,25-DHCC was found to be more effective in modulating bone turnover during orthodontic tooth movement, because its effects on bone formation and bone resorption were well balanced.