Effects of the newly developed mandibular retraction system in a rat

Authors have developed a mandibular retraction system in a rat that was constructed by arms having a metal mesh, an incisor metal cap, a pair of closed coil springs and a soft plastic collar. The merit of this system is that the anchor is very stable because it is made on the parietal bones, and the direction and load of the traction are invariable regardless of head position of the rat compared to the previous methods in which the anchor was made on the neck collar of a rat. Seventy of 8-week-old male Wistar rats were divided into five groups that were intact, collar, sham operation, straight-pull and high-pull. The anchor was implanted with a metal mesh into the subperiosteal space of the parietal bones just in front of the lambda suture of a rat. The coil spring attached on the sliding hook on the arm was connected with a hook soldered with an incisor metal cap. Therefore, the mandible was retracted in the TMJ direction (straight-pull) and some were 20 degrees upper than TMJ (high-pull) for 15 days at a tension of 10 g. All operations except for traction by the coil springs were performed on a rat in the sham operation group. Only the plastic collar was set on the neck in the collar group. Mandibular retraction for 15 days showed significant inhibition of the sagittal growth of the mandible in both high- and straight-pull groups. No inhibition of sagittal cranial growth was observed according to morphometrical and microscopical investigations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of anterior retraction and anchorage control between en masse retraction and two-step retraction: A randomized prospective clinical trial

Objectives:The purpose of this two-arm parallel trial was to compare en masse (ER) and two-step retraction (TSR) during space closure.Materials and Methods:Forty-eight adult patients with bimaxillary protrusion who were planned for treatment with extraction of four first premolars were enrolled. All patients were randomly allocated in a 1:1 ratio to either the ER (n = 24) group or the TSR (n = 24) group. The main outcome was the amount of posterior anchorage loss in the molars and the retraction of the incisors between ER and TSR; the difference in incisor and molar inclination was a secondary outcome. Lateral cephalometric radiographs and oblique cephalometric radiographs at 45° were taken before retraction (T1) and after space closure (T2). Cephalograms were digitized and superimposed on the anatomic best fit of the maxilla and mandible by one operator who was blinded to the treatment group.Results:Neither incisor nor molar crown movements showed any significant differences between the ER and TSR. There were no significant differences in the tipping of incisors and molars between the two groups.Conclusions:No significant differences existed in the amount of retraction of incisors and anchorage loss of molars between ER and TSR. Changes in incisor and molar tipping were similar, with the crowns showing more movement than the apex.     

Effects of pulsed electromagnetic field vibration on tooth movement induced by magnetic and mechanical forces: a preliminary study

BACKGROUND: This study was designed to determine whether or not high-frequency and low-magnitude vibration affects orthodontic tooth movement caused by magnetic or/and mechanical forces. METHODS: Forty-four 7-week-old Wistar rats were randomly divided into four groups, with each group further divided into experimental and control subgroups. Neodymium-Iron-Boron (Nd-Fe-B) magnets and Sentalloy closed coil springs were placed between maxillary or mandibular first molars and incisors to activate tooth movement. The animals of experimental subgroups were exposed to the vibration induced by pulsed electromagnetic fields (PEMF) whilst the control subgroups were under normal atmosphere. The experiment lasted for 14 days and all of the animals were sacrificed for examination. The changes in the space between the molar and incisor were measured to indicate the amount of tooth movement. RESULTS: The coil springs, either with sham or active magnets, move molar much more than magnets alone, regardless of absence or presence of PEMF (p < 0.001). Under PEMF, the coil spring moved significantly more amount of tooth movement than that of coil-magnet combination (p < 0.01), as did the magnets compared to sham magnets (p < 0.019). Under a non-PEMF scenario, there was no significant difference in tooth movement between coil spring and coil-magnets combination, nor was there difference between magnets and sham magnets. CONCLUSIONS: It is suggested that the PEMF-induced vibration may enhance the effect of mechanical and magnetic forces on tooth movement.     

En masse retraction and two-step retraction of maxillary anterior teeth in adult Class I women. A comparison of anchorage loss

OBJECTIVE: To compare the amount of anchorage loss of the maxillary posterior teeth and amount of retraction of the maxillary anterior teeth between en masse retraction and two-step retraction of the anterior teeth. MATERIALS AND METHODS: The sample consisted of 30 female adult patients with Class I malocclusion and lip protrusion who needed maximum posterior anchorage. The sample was subdivided into group 1 (n = 15, mean age = 21.4 years, en masse retraction) and group 2 (n = 15, mean age = 24.6 years, two-step retraction). Lateral cephalograms were taken before (T1) and after treatment (T2). Nine skeletal and 10 anchorage variables were measured, and independent t-test was used for statistical analysis. RESULTS: Although the amount of horizontal retraction of the maxillary anterior teeth was not different between the two groups, there was mild labial movement of the root apices of the upper incisors in group 2 at T2. There were no significant differences in the degree of anchorage loss of the maxillary posterior teeth between the two groups. Bodily and mesial movements of the upper molars occurred in both groups. Approximately 4 mm of the retraction of the upper incisal edges resulted from 1 mm of anchorage loss in the upper molars in both groups. CONCLUSION: No significant differences existed in the degree of anchorage loss of the upper posterior teeth and the amount of retraction of the upper anterior teeth associated with en masse retraction and two-step retraction of the anterior teeth.     

Soft-tissue profile changes resulting from retraction of maxillary incisors

The response of the soft-tissue profile to retraction of the maxillary incisors is still a matter of controversy. The purpose of this study was to improve the clinician's ability to predict the soft-tissue profile changes caused by retraction of the maxillary incisors by quantifying the profile changes, and identifying and quantifying the contribution of the most significant factors responsible for these changes. The cephalometric records of 80 Class II, Division 1 treated female subjects and 53 untreated female subjects were digitized and analyzed by means of a stepwise multiple regression analysis. The statistical assessment of the data suggested the following conclusions: In general, growth was associated with only minimal changes in the soft-tissue profile in a period not exceeding 36 months. The three clinically significant soft-tissue changes occurring in response to orthodontic treatment that included a mean upper incisor retraction of 6.7 mm were the retraction of the upper lip, the increase in the lower lip length, and the increase in the nasolabial angle. Other soft-tissue changes, which were of little clinical significance, included the retraction of the lower lip, the reduction of the interlabial gap, the increase in the thickness of both the upper and lower lips, the increase in the soft-tissue lower facial height and the lower soft-tissue component, which is the distance between lower stomion and soft-tissue menton. The length of the upper lip did not increase with either growth or orthodontic treatment. In general, changes in the lower lip in response to orthodontic tooth movement were more predictable than those of the upper lip. The low degree of predictability associated with the upper lip response to orthodontic tooth movement may be caused by the complex anatomy and/or dynamics of the upper lip, which could not be evaluated by the presently available cephalometric techniques.     

The effect of platelet-rich fibrin (PRF) on maxillary incisor retraction rate

ObjectiveTo investigate the efficiency of platelet-rich fibrin (PRF) injection on maxillary incisor retraction rate.Materials and MethodsThe study included 40 patients (23 women and 17 men; mean age; 20.7 ± 1.45) with Class II Division 1 malocclusion. The treatment plan for all patients was extraction of the maxillary first premolars and canine distalization, followed by retraction of the maxillary incisors. Patients were randomly divided into two groups. The study group received injectable platelet-rich fibrin (i-PRF) two times with an interval of 2 weeks; the control group did not receive i-PRF. In both groups, the measurements were bilaterally assessed as the distances between the lateral and canine teeth on the plaster models at five time points. The rate of incisor movement was evaluated by Student''s t-test, analysis of variance, and Tukey honestly significant difference tests. Statistical significance was set as P < .05.ResultsThe average movements of incisors were significantly higher in the study group than the control group at all time points (P < .05). According to the within-group comparison, none of the measurements showed any significant differences between the right and left sides in both groups at all time points (P > .05). While the movement of incisors was significantly higher in the study group in the week following the PRF injection compared to the other weeks (P < .05), there were no significant differences in the control group at all-time points (P > .05).ConclusionsApplying i-PRF significantly increased the rate of maxillary incisor retraction at all time intervals. Platelet-rich fibrin injection can be an effective method for shortening treatment duration.     

Effectiveness of laceback ligatures on maxillary canine retraction

OBJECTIVE: To evaluate the effects of laceback ligatures on canine distalization during the leveling and aligning stage and to compare the effectiveness of laceback ligatures with that of superelastic NiTi closed coil springs. MATERIALS AND METHODS: Fifteen subjects were included in this study. Fixed orthodontic treatment was planned with the extraction of first premolars to solve crowding in upper and/or lower arches. Stainless steel direct-bonding Roth brackets (0.022-inch) were used. For canine distalization superelastic NiTi closed coil springs generating 150 g of force were used on one side. Lacebacks made from 0.010-inch ligature wire were applied on the contralateral side. Dental and skeletal changes were evaluated from predistalization and postdistalization lateral cephalometric and submento vertical radiographs. A Wilcoxon test was applied to determine the differences between predistalization and postdistalization mean values and to determine the mean differences between the groups. RESULTS: Upper incisor crowns moved posteriorly. Distal movement and tipping of the canines were significant for both groups. Likewise, mesial movement and tipping of the first molars were significant for both groups. Furthermore, distopalatinal rotation of the canines was significant in the coil group. Canine and molar movements were greater for the coil group than for the laceback group, and the differences were significant. These differences may be attributed to force characterization, as well as to arch wire size and material. CONCLUSION: The laceback ligatures proved to be effective for canine distalization. Less canine and molar movement was found for the laceback group, but more controlled movements were obtained for the sagittal, vertical, and transverse planes.     

Unpredictability of soft tissue changes after camouflage treatment of Class II division 1 malocclusion with maximum anterior retraction using miniscrews

Objective:To compare soft and hard tissue responses based on the degree of maxillary incisor retraction using maximum anchorage in patients with Class II division 1 malocclusion.Materials and Methods:This retrospective study sample was divided into moderate retraction (<8.0 mm; n = 28) and maximum retraction (≥8.0 mm; n = 29) groups based on the amount of maxillary incisor retraction after extraction of the maxillary and mandibular first premolars for camouflage treatment. Pre- and posttreatment lateral cephalograms were analyzed.Results:There were 2.3 mm and 3.0 mm of upper and lower lip retraction, respectively, in the moderate group; and 4.0 mm and 5.3 mm, respectively, in the maximum group. In the moderate group, the upper lip was most influenced by posterior movement of the cervical point of the maxillary incisor (β = 0.94). The lower lip was most influenced by posterior movement of B-point (β = 0.84) and the cervical point of the mandibular incisor (β = 0.83). Prediction was difficult in the maximum group; no variable showed a significant influence on upper lip changes. The lower lip was highly influenced by posterior movement of the cervical point of the maxillary incisor (β = 0.50), but this correlation was weak in the maximum group.Conclusions:Posterior movement of the cervical point of the anterior teeth is necessary for increased lip retraction. However, periodic evaluation of the lip profile is needed during maximum retraction of the anterior teeth because of limitations in predicting soft tissue responses.     

下切牙内收与牙槽骨厚度变化间的相关分析

目的分析拔牙矫治后下切牙内收量与下颌颏联合处牙槽骨厚度变化间的相关关系。方法从矫治完成的安氏Ⅱ1类错[牙合]患者中，选取拔除4个第一双尖牙（组1），拔除上颌第一、下颌第二双尖牙（组2）以及下颌未矫治的非拔牙（组3）患者各15例，进行矫治前后的X线头影测量分析。结果两拔牙组牙槽点、B点及根尖处的牙槽骨厚度都明显减小（P〈0．01），而下颌未矫治组无明显变化；组1的下切牙内收量与B点及根尖处的牙槽骨厚度减小呈正相关，而组2仅与根尖处的牙槽骨厚度减小正相关。结论下切牙内收后，B点与根尖点处的牙槽骨厚度明显减小，且内收量越大该处厚度减少的越多，在临床诊疗与设计时应予以考虑。     

The effects of samarium-cobalt magnets and pulsed electromagnetic fields on tooth movement

The purpose of this study was to determine whether the application of either samarium cobalt magnets or pulsed electromagnetic fields could increase the rate and amount of orthodontic tooth movement observed in guinea pigs. In addition, the objective was to evaluate the effect of a magnetic field on bony physiology and metabolism and to monitor for possible systemic side effects. Fifteen grams of laterally directed orthodontic force were applied to move the maxillary central incisors of a sample of 18 young male Hartley guinea pigs divided into three groups: group 1, an orthodontic coil spring was used to move the incisors; group 2, a pair of samarium-cobalt magnets provided the tooth moving force; and group 3, a coil spring was used in combination with a pulsed electromagnetic field. The results showed that both the static magnetic field produced by the samarium-cobalt magnets and the pulsed electromagnetic field used in combination with the coil spring were successful in increasing the rate of tooth movement over that produced by the coil springs alone. The mechanism producing this effect appears to have involved a reduction in the “lag” phase often seen in orthodontic tooth movement. Both magnetically stimulated groups also showed increases in both the organization and amount of new bone deposited in the area of tension between the orthodontically moved maxillary incisors. (AM J ORTHOD DENTOFAC ORTHOP 1995;107:578-88.)     

Comprehensive comparison of canine retraction using NiTi closed coil springs vs elastomeric chains:: A split-mouth randomized controlled trial

ObjectivesTo compare canine retraction using NiTi closed coil springs vs elastomeric chains comprehensively in a split-mouth randomized controlled trial.Materials and MethodsThe canines in 64 quadrants were randomly retracted into the first premolar extraction spaces using NiTi closed coil springs or elastomeric chains, in the maxilla and mandible. The retraction force was 150 g. Cone beam computed tomography scans and study models were obtained before the start of canine retraction and 6 months later. The rate and total amount of canine retraction, canine rotation, tipping, and root resorption were evaluated. A visual analogue scale was used to evaluate patients'' pain experience.ResultsThe two methods were statistically similar for dental changes, rate of canine retraction, and root resorption. However, patients reported significantly more days of pain with the elastomeric chain compared to the NiTi closed coil springs.ConclusionsWithin the constraints of the current study, using either NiTi closed coil springs or elastomeric chains as force delivery systems for canine retraction results in no significant difference in the rate of canine retraction, tipping, rotation, or root resorption. Pain experience during retraction using elastomeric chains is more significant yet needs further investigation.     

附件对隐形矫治器内收上前牙影响的三维有限元分析

目的    通过拔除上颌第一前磨牙后前牙内收的隐形矫治三维有限元模型,分析切牙上设置附件对牙齿移动方式的影响。方法    基于1例成年患者颌骨的锥形束CT影像数据,按照切牙上有无附件,构建4组拔除第一前磨牙的上颌隐形矫治模型,分别为切牙无附件组、侧切牙单附件组、中切牙单附件组和双附件组;导入Ansys Workbench三维有限元软件,设置4个上切牙控根压入内收的隐形矫治过程,分析牙列初始位移和附件的应力分布。结果    切牙无附件组及中切牙单附件组均发生4个切牙的舌向倾斜移动,后牙产生不同程度的近中倾斜移动,尖牙近中倾斜伴有伸长;侧切牙单附件组及双附件组切牙呈整体内收压入移动趋势,切牙附件的龈方可观测到压应力集中。结论    隐形矫治内收上前牙时,在侧切牙放置附件有助于切牙整体内收的表达,而中切牙附件对牙移动方式的影响较小。     

The effect of two contrasting forms of orthodontic treatment on the facial profile

The purpose of this paper was to compare retrospectively the effect on the soft tissues of two contrasting forms of treatment for Class II, Division 1 malocclusion. The first group of 30 persons exhibited uncrowded dentitions and were treated without extractions by means of the Andresen activator. No other appliance was used. The second group was also composed of 30 persons. These subjects were treated with the Begg appliance in its classical form. All of the Begg subjects showed varying amounts of crowding and were treated by extraction of four first premolars. It was believed that the Andresen appliance would maintain the incisors in the most labial position possible, while the Begg group with premolar extractions would involve the maximum lingual incisal movement. These groups were compared with a third group of 22 untreated persons who also exhibited Class II, Division 1 malocclusions. The overjets in the treated groups were successfully reduced in both cases by retraction of the upper incisors; in the Begg group only, retraction of lower incisors was also performed. The upper incisors were retracted substantially more in the Begg group than in the Andresen group, but there was only a slight difference within the two groups in the final position of the upper lip relative to a vertical reference line through sella. There was also a slight difference in the lengths of upper and lower lips within the two treated groups. The lower lip followed the lower incisors more closely in the Begg group. Both upper and lower lips "uncurled" in the treated groups and this probably allowed them to be held together with little strain. There was a wide variation in individual response in all three groups.     

微种植体支抗辅助内收上切牙后牙槽骨改建的锥形束CT研究

目的:探索运用微种植体支抗结合高位牵引钩大量内收上颌切牙后牙槽骨的改建情况。方法:以22例青少年上颌前突拔牙矫治患者,上颌切牙内收前、内收完成后的锥形束CT（cone-beam CT,CBCT）为研究样本,应用Mimics 15.0行CBCT影像三维重建,明确上颌切牙移动方式,利用Invivo5.0三维定点测量唇、腭侧牙槽骨厚度和高度变化。采用SPSS19.0 软件包对测量数据进行配对t 检验。结果:上颌切牙切缘与根尖均发生水平舌侧移动,但切缘的移动距离大于根尖;切缘点发生向下移动,根尖点出现明显的向上移动。上切牙腭侧牙槽骨厚度及唇腭侧总厚度在根颈1/3和根中1/3均显著减小（P<0.05）,而根尖1/3显著增加（P<0.05）,腭侧牙槽骨高度显著降低（P<0.05）。结论:青少年上颌前突患者微种植体支抗结合高位牵引钩可以实现受控制的倾斜移动。大量内收上颌切牙后,其腭侧牙槽骨吸收远大于唇侧增生,牙槽骨并没有完全跟随牙的移动而改建,提示正畸矫治时不宜过度内收前牙。     

成人安氏Ⅱ类1分类错牙合患者正畸前后唇部软组织测量和评估

目的 测量和评估成人安氏Ⅱ类1分类错牙合患者正畸前后的唇部软组织形态. 方法 选择30例已经完成正畸治疗的安氏Ⅱ类1分类错牙合成年患者,术后模型及头影测量的数据均在正常范围内. 对其正畸前后正面像和头颅侧位片唇红的矢状向厚度和垂直向厚度进行测量. 结果 正畸后上唇垂直向厚度有变小的趋势,下唇垂直向厚度有变大的趋势,差异有统计学意义(P<0. 05). 上唇矢状向唇红部组织厚度术后有增大的趋势,下唇矢状向唇红部组织厚度矫正后有减少的趋势,且有统计学意义(P<0. 05). 上颌上中切牙(U1C)矢状向内收量与上唇红(TUL)的内收呈显著正相关,下唇红(TLL)矢状向位置的变化与下颌切牙突点(L1C)位置变化存在正相关,下唇红(TLL)矢状向位置的变化与上颌切牙突点(U1C)位置变化存在正相关. 结论 安氏Ⅱ类1分类错牙合成人患者拔牙矫治后,可以通过切牙回收量较好地预测其唇部软组织正畸前后的矢状向厚度和垂直向厚度变化.     

微型种植体与口外弓治疗成人骨性Ⅱ类错（牙合）的比较张雄单丽华赵士芳黄吉娜毛靖王虎中郭家平王蕾赵今史建陆微型种植体与口外弓治疗成人骨性Ⅱ类错（牙合）的比较

目的 比较微型种植体和口外弓作为强支抗在治疗成人骨性II类错（牙合）中的临床效果.方法 微型种植体支抗组16名,口外弓支抗组10名,收集两组治疗前后的X线头颅侧位定位片,通过X线头影测量比较两组的上下颌骨及上下颌牙齿的各角度、线距的变化.结果 两种方法在对上下颌骨的影响、覆（牙合）覆盖的控制上有相同的效果,但对上颌前后牙的移动上两种方法有明显区别（P〈0.05）,上颌磨牙近中移动量分别为1.1mm（微型种植体组）和2.6mm（口外弓组）,上颌切牙内收量8.9mm（微型种植体组）和5.5mm（口外弓组）.结论 两种加强支抗的方法在正畸治疗中均可获到较好的治疗效果,但微型种植体支抗在上颌磨牙的近中移动和上颌切牙的内收上更具有优势.     

骨皮质切开术辅助上切牙内收后对牙根及牙槽骨影响的锥形束CT研究

目的 探讨骨皮质切开术辅助上切牙内收后对上颌切牙牙根吸收、牙槽骨厚度和牙槽骨高度的影响.方法 招募20例拔除两个上颌第一前磨牙的骨性Ⅱ类1分类错牙合畸形患者,分为骨皮质切开术组(n=10)和对照组(n=10).矫治前后拍摄锥形束CT,测量两组矫治前后上颌切牙牙根长度、牙槽骨厚度和牙槽骨丧失高度.结果 骨皮质切开术组矫治疗程明显小于对照组(P<0.05);骨皮质切开术组和对照组上颌切牙牙根吸收未见明显差异(P>0.05);骨皮质切开术组治疗前后在上颌中切牙和侧切牙根中和根尖水平唇侧牙槽骨厚度的变化量大于对照组(P<0.05);骨皮质切开术组中切牙腭侧牙槽骨丧失高度量大于对照组(P<0.05).结论 骨皮质切开术辅助上切牙内收结合植骨术可以增加切牙区的牙槽骨厚度,但是在内收过程中不能减少牙根吸收,且对腭侧牙槽骨高度有一定损害.     

Ethnic differences in upper lip response to incisor retraction

INTRODUCTION: The purpose of this retrospective longitudinal study was to investigate the response of the upper lip to incisor retraction and to ascertain the effect of ethnicity on this response. METHODS: Pretreatment and posttreatment lateral cephalograms of 88 postpubertal female patients (44 black and 44 white; mean age, 18.45 years) were evaluated. The groups were matched by age and the amount of incisor retraction at incisor superius. RESULTS: Although significant pretreatment differences existed between the groups in some cephalometric measurements, analysis of the treatment changes demonstrated significant differences only in incisor inclination. Hard and soft tissue changes of the black group were more downward, whereas changes in the white group were more backward. Multivariate regression analysis showed that the horizontal response of the upper lip to hard tissue changes at subnasale and superior labial sulcus was different in whites than in blacks. At subnasale, stepwise multivariate regression analysis showed that ethnicity contributed to the upper lip response to incisor retraction and was significantly greater in the white group. CONCLUSIONS: The hard and soft tissue treatment changes of the black group were more downward, and those of the white group were more backward. Ethnic differences exist in the soft tissue response to hard tissue changes in the upper lip, and at subnasale and the superior labial sulcus; however, these response differences at superior labial sulcus can be explained by the ethnic differences in initial lip thickness and incisor inclination; they are not due in and of themselves to ethnicity. The change at prosthion was significantly correlated with the response of the upper lip at labrale superius to incisor retraction. Ethnicity added no increase to the predictability of the response. When incisor retraction was performed, the final horizontal upper lip position could be accurately and reliably predicted.     

一步法和两步法关闭间隙对不同支抗影响的研究

目的:研究安氏Ⅰ类错(牙合)患者在间隙关闭过程中分别使用一步法或两步法对上颌支抗的影响.方法:选择安氏Ⅰ类中度拥挤,拔除4个第一前磨牙,侧貌较突的女性成人患者125人,按支抗及关闭方式分为4组,分别使用强支抗和中度支抗、一步和两步滑动法关闭间隙,对其治疗前后X线投影测量结果进行分析比较.结果:无论是强支抗还是中度支抗,两步法与一步法支抗丧失量无统计学差异.使用强支抗组磨牙近移量少,支抗丧失少(P＜0.05).结论:使用一步法或两步法关闭拔牙间隙,上颌第一磨牙前移量无显著差异.强支抗引起的磨牙近移量少于中度支抗.