Effects of gradually increasing force generated by permanent rare earth magnets for orthodontic tooth movement

OBJECTIVE: To examine the effects of gradually increasing force generated by permanent rare earth magnets for orthodontic tooth movement by using a novel experimental rat model and computer simulation. MATERIALS AND METHODS: Fifty-five male rats (age 18 weeks) were used as animal experiments. Magnetic (experimental groups) or titanium (control group) cuboids (1.5 x 1.5 x 0.7 mm) were bonded to the lingual surface of the maxillary first molars. The initial distance between materials was 1.0 mm, generating 4.96 gf (experimental group I), or 1.5 mm, generating 2.26 gf (experimental group II). Tooth movement was measured and periodontal structures were observed with microfocus x-ray computed tomography radiographs. RESULTS: The distance between the magnets decreased with time in experimental groups I and II (P < .001), whereas there was no tooth displacement in the control group. Experimental group I showed rapid tooth movement in the initial phase followed by slower tooth movement. Experimental group II showed gradual tooth movement. Horizontal sections on microfocus computed tomgraphy radiographs revealed no pathological changes, such as root resorption, on the compressed side in the experimental groups. CONCLUSIONS: The initial light force and gradual increasing force in magnetic attractive force induced effective tooth movement in rats without inducing any pathological changes.     

Neutralizing effects of an anti-vascular endothelial growth factor antibody on tooth movement

Our recent studies demonstrated that local administration of recombinant human vascular endothelial growth factor (rhVEGF) during experimental tooth movement enhanced the number of osteoclasts and the rate of tooth movement. The purpose of this study was to examine the effect of anti-VEGF polyclonal antibody on osteoclastic differentiation, the amount of tooth movement, and the degree of tooth relapse in 30-day-old mice. First, these mice were subjected to various doses of anti-VEGF polyclonal antibody, with tooth movement for three days. In the next study, daily injections of 10-microg antibody were administered for 18 days during the experimental tooth movement. The amount of tooth movement was measured as in our previous study. Furthermore, in the third study, we administered daily injection of 10-microg antibody and measured tooth relapse after the experimental tooth movement for 45 days. The osteoclasts number in 10- and 50-microg antibody two-time injection group was significantly smaller than that in the controls (P < .05). The number of osteoclasts was decreased more substantially by daily injection of 10-microg antibody, showing more significant differences from the controls (P < .01). The amount of tooth movement was significantly less in the experimental group than in the controls on days 15 and 18 (P < .05). Furthermore, the amount of relapse in the experimental group was significantly less than that in the controls on days 9 and 11 after removal of the appliance (P < .05). These results show that the treatment of anti-VEGF polyclonal antibody markedly reduced the osteoclasts number and inhibited the amount of tooth movement and relapse of moved teeth.     

Epidermal growth factor in liposomes may enhance osteoclast recruitment during tooth movement in rats

OBJECTIVE: To evaluate the effects of local administration of epidermal growth factor (EGF) located within liposomes on recruitment of osteoclasts during mechanical force in rats. MATERIALS AND METHODS: An orthodontic elastic band was inserted between the left upper first and second molars, to move mesially the first molar. Rats were randomly divided into 4 groups (n = 8): EGF (2 ng/microL) located within liposomes (group 1), liposomes only (group 2), soluble EGF (2 ng/microL; group 3), or vehicle alone (group 4). The solutions were injected into the region of the root furcation of the left first molar after elastic band insertion. Tooth movement was measured using a plaster model of the maxilla, and the number of osteoclasts recruited at the pressure side of the first molar was histologically evaluated. RESULTS: Intergroup analysis showed that there was no significant difference between group 2 and group 4 (P > .05) and between group 1 and group 3 (P > .05). However, group 1 and group 3 exhibited greater differences in tooth movement than group 2 and group 4 (P < .05). On the other hand, group 1 showed greater tooth movement than groups 2 and 4 with statistical significance (P < .01). The increase in the number of osteoclasts in group 1 was significantly higher than in the other groups (P < .05). CONCLUSION: Exogenous EGF-liposome administration has an additive effect when compared with soluble EGF on the rate of osteoclast recruitment, producing faster bone resorption and tooth movement.     

The effect of pregnancy on orthodontic tooth movement in rats

Introduction: The purpose of this study was to investigate the effect of pregnancy on orthodontic tooth movement in Wistar rats. Material and Methods: Forty eight female three-month old Wistar rats with an average weight of 250±25 gr were selected and randomly divided into two experimental (pregnant) and control groups (non-pregnant). Maxillary central incisors were tipped distally by insertion of springs exerting 30g force. Two, seven and fourteen days after spring insertion animals were sacrificed. Then the mesioincisal distance between maxillary incisors were measured. Subsequently, histological sections were prepared to count osteoclasts under a light microscope. The data on the extent of orthodontic tooth movement, and the number of osteoclasts were analyzed by independent sample t-test. Results: The results indicated that 2,7 and 14 days after force application there was no significant difference in orthodontic tooth movement between experimental and control groups (p>0.05). The number of osteoclasts were significantly lower in the experimental group 7 and 14 days after spring insertion (p<0.05). Conclusion: Pregnancy may decrease the amount of tooth movement in the linear phase but it is not statistically significant. The number of osteoclasts is significantly decreased during pregnancy. Key words:Pregnancy, rat, orthodontic tooth movement, osteoclast.     

外源性TGF-β1与PDGF-BB联合应用对正畸牙压力侧Pyk2蛋白和基因表达的影响

目的 探讨外源性生长因子-β1与外源性血小板衍生生长因子BB联合应用对牙周组织破骨细胞内Pyk2表达的影响。方法 160只SD大鼠随机分为2组,建立正畸牙移动模型。A组注射含rhTGF-β1与rhPDGF-BB的混合液 0.1 mL,B组注射相同容量的PBS。加力后1、4、7、10、14 d,分别处死每大组的1小组大鼠。测量牙移动距离变化,TRAP染色行破骨细胞计数,Pyk2蛋白和基因水平分别用免疫组织化学染色法和RT-PCR检测。采用SPSS19.0软件包对数据进行统计学分析。结果 2组牙移动距离在第4、7、10、14天均具有统计学差异（P<0.05）。A组压力侧破骨细胞计数显著高于B组,除第14天外,其余各时间点均具有显著差异（P<0.05）。A组Pyk2蛋白和基因表达均比B组高,2组均在第7天达到最高峰,除第1天外,其余时间点Pyk2蛋白表达均具有统计学差异（P<0.05）。第4、7天,2组Pyk2基因表达均具有统计学差异（P<0.05）。结论 外源性TGF-β1与PDGF-BB联合应用可从蛋白和分子水平上调正畸牙牙周组织压力侧Pyk2的表达,这可能是加速正畸牙移动速率的原因之一。     

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。     

Rapid Palatal Expansion in Mixed Dentition Using a Modified Expander: a Cephalometric Investigation

Abstract

Aim: To investigate light forces for experimental tooth movement.

Method: Light orthodontic forces of 1.2, 3.6, 6.5, and 10 g force (gf) were applied for 14 days to move rat molars, and the effects of the forces on the rate of tooth movement and changes of the periodontium were examined.

Results: In the early period, despite the different levels of force used in each group, there were no significant differences in tooth displacement. From hour 56 to day 14, the tooth displacement in the 1.2 gf group was significantly smaller than that in the other groups and the rate was nearly constant. The rates of tooth displacement in the 3.6, 6.5, and 10 gf groups fluctuated repeatedly, while the orthodontic forces gradually decreased.

Conclusion: Experimental tooth movement in rats, tipping without friction under light forces, were either constant or fluctuated in cycles of several days' duration. This is in contradiction to the three-phases-theory of tooth movement described in previous investigations using heavy forces.     

正畸移动后大鼠牙周炎牙整合素β1mRNA变化的实验研究

目的　研究正畸移动后大鼠牙周炎牙与正常牙整合素β1 mRNA表达的变化。方法　选用10周龄雄性成 年SD大鼠96只,随机分为正常牙组、牙周炎牙组,每组48只。分别在加力后0、1、2、3、5、7 d点处死动物,制备标 本,采用原位杂交检测牙周炎牙与正常牙正畸移动后β1 mRNA转录水平的变化。结果　正常牙组和牙周炎组加力 后各时间点的整合素β1 mRNA阳性强度均较加力前有明显增高(P<0·001);在加力各时间点,两组整合素β1 mRNA的表达强度均无显著性差异(P>0·05)。结论　在牙移动中,整合素β1 mRNA牙周组织破骨细胞上有强表 达,提示其与牙移动中牙周组织的稳定和改建有关。     

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.     

超声波加速正畸牙移动的实验动物研究

目的:在大鼠正畸模型中,对第一磨牙牙周组织施加超声波振动,观察超声波是否能加速正畸牙移动。方法:选用30只SD大鼠,建立以中切牙为支抗,移动单侧第一磨牙的正畸模型,分为常规正畸组和超声波振动组。于加力第7、14、28天测量牙移动距离,HE染色,trap染色破骨细胞计数,Masson染色观察第一磨牙牙周组织的变化。结果:牙周组织接受超声波振动刺激后,大鼠第一磨牙在第7、14、28天移动速率显著高于常规正畸组(P<0.05);同时可观察到超声波振动组中TRAP阳性的破骨细胞显著多于常规正畸组(P<0.05)。而Masson染色则显示,在加力第7天,常规正畸组和超声波振动组中,皆出现新生骨;但第14天时,前者新骨形成更加明显;直到第28天超声波后者出现更大规模的成骨反应。结论:超声波显著、并持续地增加牙周组织内破骨细胞形成数量,此效应可能导致了大鼠正畸模型的牙齿移动的加速,成功建立超声波加速正畸牙移动的实验动物模型。     

Later orthodontic appliance reactivation stimulates immediate appearance of osteoclasts and linear tooth movement

Background: Delays in the appearance of osteoclasts at compression sites occur after orthodontic appliance reactivation, when this is done during both the period of osteoclast recruitment and the peak expansion in the osteoclast population. This experiment examines osteoclasts and tooth movement in alveolar bone after appliance reactivation coinciding with alveolar bone formation and the time when reactivation osteoclasts first appear (ie, 10 days after initial appliance activation). Methods: Bilateral orthodontic appliances were activated to mesially tip maxillary molars with 40 cN in 144 rats. After 10 days, all rats were randomized into two groups of 72. Group I had appliances reactivated in precisely the same manner as the first activation. Group II had appliances sham-reactivated. Nine to 12 rats were then sacrificed at 1, 3, 5, 7, 10, and 14 days in both groups (eg, day 1 represents an interval of 11 days after the first appliance activation and 1 day after either sham or real reactivation). Orthodontic movement was measured cephalometrically; changes in osteoclasts and root resorption were assessed at both compression and tension sites histomorphometrically. Results: Teeth in the reactivated group (Group I) displayed linear tooth movement (62.6 μm/day), and 0.9 mm tooth movement by day 10. Significant increases in osteoclast numbers, osteoclast surface percentage, and surface per individual osteoclast were evident in these animals by 1 day postreactivation (P < .01). Significant treatment-related increases in root resorption were not evident at compression sites at any time. Conclusions: These findings indicate that, after appliance reactivation during the time when reactivation osteoclasts appear, a second cohort of osteoclasts can be recruited immediately, along with immediate and substantial tooth movement and no greater risk of root resorption. (Am J Orthod Dentofacial Orthop 1998;114:692-7)     

Role of polycystin-1 in bone remodeling: Orthodontic tooth movement study in mutant mice

Objective:To test the hypothesis that polycystin-1 (PC1) is involved in orthodontic tooth movement as a mechanical sensor.Materials and Methods:The response to force application was compared between three mutant and four wild-type 7-week-old mice. The mutant mice were PC1/Wnt1-cre, lacking PC1 in the craniofacial region. An orthodontic closed coil spring was bonded between the incisor and the left first molar, applying 20 g of force for 4 days. Micro–computed tomography, hematoxylin and eosin staining, and tartrate-resistent acid phosphatase (TRAP) staining were used to study the differences in tooth movement among the groups.Results:In the wild-type mice the bonded molar moved mesially, and the periodontal ligament (PDL) was compressed in the compression side. The compression side showed a hyalinized zone, and osteoclasts were identified there using TRAP staining. In the mutant mice, the molar did not move, the incisor tipped palatally, and there was slight widening of the PDL in the tension area. Osteoclasts were not seen on the bone surface or on the compression side. Osteoclasts were only observed on the other side of the bone—in the bone marrow.Conclusions:These results suggest a difference in tooth movement and osteoclast activity between PC1 mutant mice and wild-type mice in response to orthodontic force. The impaired tooth movement and the lack of osteoclasts on the bone surface in the mutant working side may be related to lack of signal from the PDL due to PC1 deficiency.     

组织工程修复区早期牙移动压力侧牙周组织的改建

目的: 探讨牙槽骨组织工程修复区内早期牙移动时压力侧的牙周改建情况,为组织工程技术在正畸中应用的安全性和可行性提供实验依据。方法: 选取30只新西兰大白兔,通过拔除下颌第一磨牙并扩大拔牙窝,建立双侧牙槽骨的超临界骨缺损,分别以实验组骨髓间充质干细胞（bone marrow mesenchymal stem cells,BMSCs）与颗粒型多孔β磷酸三钙（beta-tricalcium phosphate,β-TCP）支架复合构成的组织工程骨和对照组单纯β-TCP支架进行右侧和左侧骨缺损修复。术后8周,选取6只兔进行植骨区取材,评价2组的成骨效果。对剩余兔进行下颌两侧第二磨牙加力,近中向牵引4周。分别在加力后的第1、2、3、4周各处死6只动物,测量牙移动距离并制作组织学切片,通过H-E染色观察牙周组织变化,抗酒石酸酸性磷酸酶染色法计数压力侧破骨细胞数目。采用SPSS 19.0软件包对数据进行统计学分析。结果: 植骨术后8周,实验组成骨效果优于对照组。牵引4周后,正畸牙在实验组牙槽骨修复区内的移动量大于对照组。牵引第2、3、4周时,实验组移动牙压力侧的破骨细胞数量均高于对照组,差异具有统计学意义。结论: BMSCs复合β-TCP支架能够良好地修复牙槽骨缺损,邻牙在组织工程修复区内早期移动时,再生的牙周组织改建活跃,有加速牙移动的趋势。     

The effect of oral contraceptives on orthodontic tooth movement in rat

Introduction: The purpose of this study was to investigate the effect of ethinyl estradiol/norgestrel � used in some oral contraceptives- on orthodontic tooth movement in Wistar rats. Material and Methods: Forty eight female three-month old Wistar rats with an average weight of 250�25gr were divided into two experimental and control groups. One week prior to appliance insertion and during the appliance therapy period, 100 mcg/kg/day of ethinyl estradiol and 1mg/kg/days of norgestrel were administered to the experimental group by gavage; meanwhile the control group received an equivalent volume of Sodium Chloride 0.9 % (Saline). Maxillary central incisors were tipped distally by insertion of springs exerting 30g force. Two, seven and fourteen days after spring insertion animals were sacrificed. The mesioincisal distance between maxillary incisors were measured. Subsequently, histological sections were prepared for histomorphometric studies. Results: 14 days after force application the orthodontic tooth movement was significantly lower in the experimental group (p<0.05). The number of osteoclasts were significantly lower in the experimental group 2, 7 and 14 days after spring insertion (p<0.05). Conclusion: Ethinyl estradiol/norgestrel (oral contraceptives) can significantly decrease the amount of tooth movement in the linear phase. Key words:Oral contraceptives, orthodontic tooth movement, ethinyl estradiol, norgestrel.     

局部应用二磷酸盐对鼠正畸牙移动影响的研究

目的 探讨局部注射Zoledronate溶液对鼠正畸牙齿移动距离与牙周组织形态的影响。方法 选用42只雄性Wistar大鼠，牵引其上颌第一磨牙近中移动。实验中分别将Zoledronate溶液及生理盐水注射入实验组（左侧）及对照组大鼠（双侧）上颌第一磨牙腭侧的粘骨膜下。注射于实验前3d开始，共进行9次，每3d一次。分别在加力0、3、7、14、21d后记录上颌第一磨牙移动距离，组织HE染色后，观察牙周组织形态学的改变。结果 ①实验组大鼠牙齿移动距离明显低于对照组。②实验组大鼠压力侧破骨细胞数在实验全过程中均低于对照组，而根分叉区破牙骨质细胞数除加力14d外，2组差异无显著性。③实验过程中Zoledronate溶液对破骨细胞和破牙骨质细胞以外的细胞作用不明显。结论 Zoledronate能有效地抑制支抗牙移动，减少压力侧牙槽骨表面破骨细胞数。     

Electron microscopic study of periodontal tissues in the pressure side by intermittent forces

The intermittent forces (10g and 30g) were applied to the upper right first molars of mature Wistar rats to move them lingually for 1, 5 and 9 days with wire springs. The periodontal tissues in the pressure side were investigated light/electron-microscopically and cytochemically (localization of acid phosphatase activity). The periodontal tissues in the pressure side divided into the following three areas were observed. The area I: The area of hyalinized tissues. The area II: The area situated within 100 microns from the end of hyalinized tissues. The area III: The area situated within 100 microns from the border of area II. The following results were obtained. I Tooth movement Experimental teeth applied with 30 g were moved much more than those applied with 10g. II Light microscopic findings 1) The narrowness of the periodontal space in the area I was not observed remarkably on 1 and 5 day experiment of 10g and 1 day experiment of 30g, though hyalinized tissues had appeared in them. 2) Semi-hyalinized tissues observed in some parts of area II degenerated into hyalinized tissues during the experimental periods. 3) Direct resorption of alveolar bone by osteoclasts was seen initially in the area III on 5 day experiment of 10g and 1 day experiment of 30g. III Electron microscopic findings 1) The hyalinized tissues (area I) and semi-hyalinized tissues (some parts of area II) were characterized to contain only a few necrotic cells and cell debris. The localization of Acpase activity could not be seen in these cells and cell debris. 2) Fibroblasts in the area II and III showed various appearances; autophagy, heterophagy of collagen fibrils, fusion with other fibroblasts and cell degeneration. And the localization of Acpase-activity was observed remarkably in lysosomes, secondary lysosomes and Golgi apparatus. A few macrophages were observed in the area II and III, but the other inflammatory cells and foreign body giant cells could not be seen. 3) On the other hand, active and inactive osteoclasts were seen on the bone surface in both area II and area III.     

大鼠牙周炎牙正畸移动后整合素β_3mRNA变化的实验研究

目的研究大鼠牙周炎牙及其正常牙在正畸移动中整合素β3mRNA的表达变化.方法选用10周龄雄性成年SD大鼠96只,随机分为正常牙组、牙周炎牙组,每组48只.分别在加力后0 d、12 h、1 d、3 d、5 d、7 d每一时间点处死8只动物,制备标本.采用原位杂交检测牙周炎牙与正常牙正畸移动后β3mRNA转录水平的变化.结果正常牙组和牙周炎牙组加力后12 h和3 d时的牙周膜内破骨细胞整合素β3mRNA阳性强度均较加力前有明显增加(P＜0.001);其余时间点未见整合素β3mRNA阳性表达.在加力各时间点,两组整合素β3mRNA的表达强度无显著性差异(P＞0.05).结论在正常牙及牙周炎牙移动早期,牙周膜和牙槽骨骨髓腔内有整合素β3mRNA表达,提示整合素β3可能参与破骨细胞前体向破骨细胞转化及破骨细胞迁移和粘附.     

Effect of appliance reactivation after decay of initial activation on osteoclasts, tooth movement, and root resorption

Clinical orthodontists frequently reactivate appliances following decay. Studies of tooth movement and tissue responses following reactivations indicate that linear tooth movement and rapid recruitment of osteoclasts can be achieved if reactivation is timed to coincide with the latter part of the bone remodeling cycle initiated by the first activation. Both can be delayed if reactivations are timed for the early part of the previous cycle. The objective of this study was to examine tooth movement, root resorption, and osteoclast recruitment following appliance reactivation after the first activation had decayed. Bilateral orthodontic appliances were activated with 40 cN in 144 rats to mesially tip the maxillary molars. After 16 days, rats were randomized into two groups of 72. In group 1, appliances were reactivated in precisely the same manner as the first activation. In group 2, appliances were sham-reactivated. Rats were sacrificed at 1, 3, 5, 7, 10, and 14 days. Orthodontic movement was measured cephalometrically; changes in osteoclasts and root resorption were assessed at both compression and tension sites histomorphometrically; tartrate-resistant acid phosphatase (TRAP) was measured in alveolar bone and serum biochemically. Orthodontic tooth movement was linear in group 1, but osteoclasts required 3 to 5 days to appear. There were no group- or time-related differences in root resorption. Bone TRAP levels were elevated in both groups but dropped significantly (p<0.01) in group 2 at day 7. Appliance reactivations that followed decay of the first activation produced efficient tooth movement without increased risk of root resorption, but these changes were not accompanied by rapid osteoclast recruitment at compression sites. Timing appliance reactivations for the latter portion of the previous bone remodeling cycle could have significant clinical advantages because the delay period seen in tooth movement following a single activation or short-term reactivation can be avoided.     

不同双膜透明矫治器戴用时间对正畸牙移动效果影响的实验研究

目的 探讨不同双膜透明矫治器戴用时间对正畸牙移动效果的影响。方法 选取9只新西兰大白兔,随机分为实验1组、实验2组和对照组,每组3只。对两个实验组动物采用薄膜（0.625 mm）和厚膜（0.750 mm）两种厚度膜片透明矫治器进行矫治,均设计为每一步矫治使左右下中切牙各远中移动0.33 mm,总矫治时长为12 d;其中实验1组（缩短薄膜矫治器戴用时间）的每步矫治时长为3 d（薄膜矫治器1 d、厚膜矫治器2 d）,共进行4步矫治;实验2组的每步矫治时长为4 d（薄膜矫治器2 d、厚膜矫治器2 d）,共进行3步矫治。对照组配戴厚膜矫治器,但不进行牙移动。测量矫治前及每步矫治结束后实验动物临床冠切点、中点、龈点的牙移动相关指标。对实验组每一步矫治前后及两个实验组之间的牙移动量、牙移动速率及牙移动表达精确度进行比较分析。结果 （1）戴用双膜透明矫治器可有效完成牙移动,与矫治前比较,牙移动量具有统计学意义（P < 0.05）;（2）同一位点实验1组牙移动速率均高于实验2组（P < 0.05）;（3）实验1组缩短薄膜佩戴时间,与实验2组的单步矫治牙移动量差异无统计学意义（P > 0.05）;（4）在进行同一步骤矫治时,实验1组龈点牙移动表达精确度稍低于实验2组,在切点和中点两组的牙移动表达精确度无差异;（5）实验1组和实验2组的牙移动方式均为倾斜移动,且两组的倾斜程度差异无统计学意义（P > 0.05）。结论 （1）缩短薄膜戴用时间可有效提高牙移动速率,且牙移动量无明显差异,但龈点牙移动量表达精确度可能稍有降低;（2）临床可适当缩短薄膜戴用时间,以提高正畸牙移动速率,并可缩短疗程、优化患者感受,尤其适用于需要倾斜移动的病例。     

减阻牵张快速牙移动中TGF-β1表达变化对牙周组织改建的影响

目的 探讨减阻牵张快速牙移动中转化生长因子β1（TGF-β1）在牙周组织改建中的作用。方法 20 只 Beagle 犬随机均分为加力 5、10、15 d、加力 15 d 保持 10、90 d 5组。于下颌骨两侧随机分别采用减阻牵张（实验组）和常规正畸方法（对照组）移动第一前磨牙。各组犬分别于预定时间测量牙移动距离并获取第一前磨牙牙周组织块,进行 H-E、苦味酸-天狼星红、免疫组化染色观察。采用SPSS 18.0软件包对数据进行统计学分析。结果 实验组牙移动及牙周改建速度显著快于对照组;2组TGF-β1阳性表达分布区域相似,均于15 d骨生成最活跃阶段达到峰值,但加力各阶段实验组阳性表达显著高于对照组（P<0.05）。结论 与常规正畸方法相比,减阻牵张能明显增加移动牙张力侧牙周组织TGF-β1的表达,加速牙周组织改建。