控轴矫治系统下颌尖牙及牙周组织三维有限元模型的建立

目的 建立带尖牙控轴托槽的下颌尖牙及其支持组织的三维有限元模型,初步进行有限元力学分析。方法 CBCT扫描获取下颌尖牙的断层图像,通过Mimics 14.0软件生成尖牙实体模型,并使用Pro/ENGINEER 4.0建模软件建立尖牙控轴托槽的实体模型,最后利用Ansya l4.5有限元分析软件建立有限元模型并进行分析。结果 建立了带控轴托槽的下颌尖牙及其支持组织的有限元模型,模型由5种材料属性、6个实体组成,具有良好的几何相似性和力学相似性,符合有限元计算要求,并初步分析了远中牵引尖牙的有限元力学情况。结论 本研究所建立的模型与临床情况接近,能够满足生物力学分析的要求,为进一步力学研究奠定理论基础。     

常用国产、进口正畸托槽的槽沟宽度精度及表面光洁度的比较

目的比较临床常用的国产金属直丝弓托槽和进口金属直丝弓托槽槽沟宽度及其精度、槽沟近远中截面光洁度和结扎翼光洁度。方法采用施奈德坐标测量仪对4种国产金属直丝弓托槽和4种进口金属直丝弓托槽放大30倍后进行测量。结果国产托槽和进口托槽槽沟的近、远中宽度均有良好的一致性,但国产托槽和进口托槽槽沟宽度普遍大于设计值;进口托槽槽沟近远中端截面的光洁度优于国产托槽,国产托槽结扎翼表面光洁度已达到进口托槽结扎翼表面光洁度水平。结论绝大部分国产和进口直丝弓金属托槽槽沟宽度较设计值大,个别品牌托槽槽沟宽度显著大于设计值。国产和进口金属托槽结扎翼表面均有较好的抛光度,但国产托槽槽沟内的抛光工艺尚待提高。     

不同托槽与弓丝之间动态摩擦力的研究

目的 :研究正畸过程中牙移动时托槽与弓丝之间的动态摩擦力。方法 :设计了体外装置模拟牙移动时托槽与弓丝的关系 ,分析尖牙远中移动时托槽与弓丝之间的动态摩擦力。结果 :对目前临床常用的七种托槽与五种不同弓丝在不同结扎方式下的动态摩擦力进行了研究 ,得出了托槽与弓丝之间的动态摩擦力。结论 :不同的托槽、不同弓丝以及不同结扎方式对摩擦力的影响均有显著性意义。     

Lock-loose托槽与传统托槽摩擦力特性的比较研究

目的 在干燥和人工唾液环境中测量Lock-loose托槽结扎中间翼和结扎全翼时与弓丝之间滑动摩擦力和静摩擦力的大小,并与传统四翼托槽和自锁托槽进行对比。方法 应用原子力显微镜观察不锈钢弓丝与不同托槽摩擦前后的表观形貌。选用Lock-loose托槽、传统四翼托槽和自锁托槽,分别与0.406 4 mm、0.457 2 mm不锈钢圆丝和0.457 2 mm×0.634 9 mm、0.482 6 mm×0.634 9 mm不锈钢方丝组合,其中Lock-loose托槽使用结扎中间翼和结扎全翼两种结扎方式。使用电子万能力学实验机测量干燥和人工唾液两种环境下弓丝在托槽内滑动的动、静摩擦力。结果 不同尺寸弓丝与不同托槽摩擦前后的表面粗糙度无明显差异（P>0.05）;Lock-loose托槽结扎中间翼与4种弓丝组合的动、静摩擦力均接近于0,与传统四翼托槽有明显差异（P<0.05）;与0.457 2 mm×0.634 9 mm不锈钢方丝组合时,Lock-loose托槽结扎全翼可以获得最大动、静摩擦力,与传统四翼托槽和自锁托槽的差异有统计学意义（P<0.05）;人工唾液环境中的摩擦力小于干燥环境中的摩擦力（P<0.05）。结论 Lock-loose托槽可以通过不同的结扎方式调节并获得临床所需的摩擦力,有效解决了低摩擦力与强支抗控制的矛盾问题。     

自锁托槽矫治技术的临床研究进展

自锁托槽自问世以来不断改进发展,代表了直丝弓矫治器的发展方向.自锁托槽通过闭锁结构替代了传统托槽橡皮圈或结扎丝对弓丝的结扎,根据其对弓丝的加力方式主要分为主动自锁托槽与被动自锁托槽.因自锁托槽无需结扎,临床操作方便、快捷,节省椅旁工作时间,摩擦力低,在正畸临床应用中日趋广泛,本文就自锁托槽临床应用中矫治力的选择、矫治时...     

介绍一种结扎严重错位牙的方法

正畸病例中常见个别严重错位牙如上颌侧切牙腭向错位 ,上颌尖牙唇向低位等等。矫治过程中 ,因为错位牙距弓丝距离过远。弓丝常常不能完全入槽需要用结扎丝悬吊 ,“妥协”结扎 ,此时在方丝弓或直丝弓托槽上结扎操作较为困难。若结扎过紧 ,牙齿受力过大 ,且托槽易脱落 ;结扎过松 ,牙齿稍做移动后结扎丝又很容易变松脱落 ,影响治疗。由于牙齿错位严重 ,为了保持牙弓形状 ,此时常常需要用较硬的弓丝 ,结扎时上述问题更加突出 ,有时不得不用辅弓或在弓丝上弯制各种曲来使错位牙排入牙列 ,临床操作繁琐 ,增加了椅旁工作时间和医生劳动强度。附图　…     

欧米加阻挡曲扩弓法排齐和整平下颌拥挤牙列效果的临床研究

目的 评价下颌非拔牙病例中,澳丝弯制的欧米加阻挡曲扩弓法在传统直丝弓托槽上排齐和整平下颌拥挤牙列方面的临床效果。方法 选择58例正畸患者,年龄19~24岁,随机均分成2组,各29例,一组接受传统矫治方法,另一组采用欧米加阻挡曲扩弓法矫治。每种矫正方法又分为轻-中度拥挤（5 > Ⅱ > 2）和重度拥挤（Ⅱ > 5）两个亚组。下颌治疗结束时间以下牙弓完全排齐和整平为准。头颅侧位片评价下牙弓排齐和整平前后下切牙位置的变化;模型上测量下尖牙间距和下第一恒磨牙间距以反映牙弓宽度的变化。结果 2种排齐和整平的方法获得了相同程度的前牙区和后牙区扩弓量;就重度拥挤病例而言,欧米加阻挡曲扩弓法要明显快于传统方法（P=0.017）;结论 2种方法无论在切牙的唇向移动程度还是尖牙间距和磨牙间距的扩大情况等各方面几乎获得了同样的效果,对于严重拥挤的牙列,欧米加阻挡曲扩弓装置显示出更高的效率,是非常值得推荐的一种矫正方法。     

改良滑动直丝弓托槽的竖沟设计对支抗的影响

目的研究改良滑动直丝弓托槽背板上的竖沟设计在拉尖牙向远中移动的过程中的作用,检验此设计在减小摩擦力节省支抗方面是否有效。方法选用Ⅱ°~Ⅲ°拥挤的AngleⅠ类错患者28例,年龄14~25岁,均拔除四个第一双尖牙,使用杭州西湖巴尔公司生产的改良滑动直丝弓矫治器进行矫治。在拉尖牙向远中移动的过程中,对尖牙采用竖结扎,在尖牙与第一磨牙之间挂弹性橡皮圈,力值为90~100g。在拉尖牙之前及尖牙与第二双尖牙并拢之后,分别进行模型测量和X线头影测量,并进行统计学分析。结果上颌尖牙远中移动的距离与上颌磨牙近中移动距离之比为11.161;下颌尖牙远中移动的距离与下颌磨牙近中移动距离之比为5.941。上下颌切牙均有明显内收。结论改良滑动直丝弓托槽的竖沟设计及尖牙的竖结扎,在拉尖牙向远中移动的过程中减小了尖牙托槽与主弓丝之间的摩擦力,节省了支抗,并符合差动力的原理。改良滑动直丝弓矫治器的使用可为错畸形的矫治提供强支抗,从而省去了使用口外弓等其它增强支抗的方法,使滑动直丝弓矫治器的使用更加简便。     

改良滑动杆远中移动尖牙

笔者将滑动杆作改良设计 ,用于取代开大螺旋簧推尖牙向远中 ,获得了良好的临床效果。　　作者单位 :42 3 0 0 0湖南省郴州市第一人民医院口腔科　　 1.材料和方法 :改良滑动杆用 0 .4ｍｍ澳丝弯制 ,滑动杆固位部分高度约 4ｍｍ。中切牙与尖牙之间放置滑动杆者 ,用 0 .45ｍｍ澳丝弯制滑动杆 ,中切牙应作连续结扎 ,滑动杆长度为中切牙托槽远中翼端与尖牙托槽近中翼端距离再加3ｍｍ。尖牙间放置滑动杆者 ,用 0 .45ｍｍ澳丝弯制滑动杆 ,长度为尖牙托槽近中翼端间距加 3ｍｍ ,把滑动杆小圈曲结扎在弓丝上 ,经临床测试改良滑动杆受压 3ｍｍ ,将产…     

正畸治疗中上前牙压入的Typodont研究

目的 :运用Typodont对方丝弓矫治器上应用Vbends弓托槽翼上结扎压低上前牙进行实验研究。 方法 :在Typodont上对Vbends弓托槽翼上结扎 ,托槽槽沟内结扎以及连续摇椅弓三种压低上前牙的方法进行对比研究。结果 :Vbends弓托槽翼上结扎方法在上前牙的压入及支抗磨牙控制方面的效果较好。结论 :Vbends弓托槽翼上结扎是正畸临床可以选用的一种压低上前牙的方法     

国产3B自锁托槽、3B直丝弓托槽和Damon Q自锁托槽椅旁操作时间的对比研究

目的比较国产3B自锁托槽、Damon Q自锁托槽以及国产3B直丝弓托槽的椅旁操作时间,为国产3B自锁托槽的临床应用提供参考依据。方法选择正畸患者80例,其中20人使用国产3B自锁托槽(3B自锁组),20人使用Damon Q自锁托槽(Damon Q自锁组),20人使用国产3B直丝弓托槽+结扎丝结扎(结扎丝组),20人使用国产3B直丝弓托槽+橡皮圈结扎(橡皮圈组)。待患者上下颌牙列基本排齐后,使用0.018*0.025英寸镍钛方丝入槽,记录全口结扎和拆除时间。采用单因素方差分析,比较4组患者的结扎和拆除时间。结果 3B自锁组的结扎、拆除和总时间均明显短于结扎丝组和橡皮圈组(P<0.01)。3B自锁组和Damon Q自锁组在结扎、拆除和总时间方面的差异均无统计学意义(P>0.05)。结论无论是采用结扎丝结扎还是橡皮圈结扎,国产3B自锁托槽的椅旁操作时间明显短于直丝弓托槽,且与进口的Damon Q自锁托槽相比无明显统计学差异。     

Physical and chemical properties of orthodontic brackets after 12 and 24 months: in situ study

Objective

The aim of this article was to assess how intraoral biodegradation influenced the surface characteristics and friction levels of metallic brackets used during 12 and 24 months of orthodontic treatment and also to compare the static friction generated in these brackets with four different methods of the ligation of orthodontic wires.

Material and Methods

Seventy premolar brackets as received from the manufacturer and 224 brackets that were used in previous orthodontic treatments were evaluated in this experiment. The surface morphology and the composition of the deposits found in the brackets were evaluated with rugosimetry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Friction was analyzed by applying tensile tests simulating sliding mechanics with a 0.019x0.025" steel wire. The static friction levels produced by the following ligation methods were evaluated: loosely attached steel ligature around all four bracket wings, steel ligature attached to only two wings, conventional elastomeric ligation around all 4 bracket wings, and non-conventional Slide^® elastomeric ligature.

Results

The results demonstrated the presence of biodegradation effects such as corrosion pits, plastic deformation, cracks, and material deposits. The main chemical elements found on these deposits were Carbon and Oxygen. The maximum friction produced by each ligation method changed according to the time of intraoral use. The steel ligature loosely attached to all four bracket wings produced the lowest friction levels in the new brackets. The conventional elastic ligatures generated the highest friction levels. The metallic brackets underwent significant degradation during orthodontic treatment, showing an increase in surface roughness and the deposit of chemical elements on the surface.

Conclusion

The levels of static friction decreased with use. The non-conventional elastic ligatures were the best alternative to reduce friction.     

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??Objective    To observe the change of the surface structure of the arch wire due to different orthodontic bracket designs and ligations. Methods    In the dry environment the sliding of bracket  on the arch wire was simulated??and WDW20 & 0.5 electronic universal testing machine was used to provide uniform traction??the arch wire was scanned with SEM. Results    The wires investigated in this study had varying degrees of change??the MLF bracket with 0.2 mm ligation group had minimal changes to the arch wire surface. The scratches of arch wire surface distributed evenly on elastic ligation ring group??0.25 mm ligature wire was likely to cause the uneven distribution of stress. Conclusion    The different ways of ligation have different effects on morphological structure of the surface of the arch wire. The coarser ligature wires have bigger influence on the arch wire surface structure. Different orthodontic bracket designs will change the arch wire surface structure.     

Forces in the presence of ceramic versus stainless steel brackets with unconventional vs conventional ligatures

OBJECTIVE: To compare the forces resulting from four types of bracket/ligature combinations: ceramic brackets and stainless steel brackets combined with unconventional elastomeric ligatures (UEL) and conventional elastomeric ligatures (CEL) during the leveling and aligning phases of orthodontic therapy. MATERIALS AND METHODS: The testing model consisted of five 0.022-inch preadjusted brackets (second premolar, first premolar, canine, lateral incisor, and central incisor) for each of the two bracket types. The canine bracket was welded to a sliding bar that allowed for different amounts of offset in the gingival direction. The forces generated by a 0.014-inch superelastic nickel titanium wire in the presence of either the UEL or CEL bracket/ligature systems at different amounts of upward canine misalignment (1.5 mm, 3 mm, 4.5 mm, and 6 mm) were recorded. RESULTS: Significant differences were found between UEL and CEL systems for all tested variables (P < .01) with the exception of the canine misalignment of 1.5 mm. The average amount of recorded force in the presence of CEL was negligible with 3.0 mm or greater of canine misalignment. On the contrary, during alignment, a force available for tooth movement was recorded in the presence of both ceramic and stainless steel brackets when associated with UEL. CONCLUSIONS: The type of ligature used influenced the actual amount of force released by the orthodontic system significantly more than the type of bracket used (stainless steel vs ceramic).     

Torque Expression in Stainless Steel Orthodontic Brackets: A Systematic Review

Objective:To evaluate the quantitative effects on torque expression of varying the slot size of stainless steel orthodontic brackets and the dimension of stainless steel wire, and to analyze the limitations of the experimental methods used.Materials and Methods:In vitro studies measuring torque expression in conventional and self-ligating stainless steel brackets with a torque-measuring device, with the use of straight stainless steel orthodontic wire without second-order mechanics and without loops, coils, or auxiliary wires, were sought through a systematic review process.Results:Eleven articles were selected. Direct comparison of different studies was limited by differences in the measuring devices used and in the parameters measured. On the basis of the selected studies, in a 0.018 inch stainless steel bracket slot, the engagement angle ranges from 31 degrees with a 0.016 × 0.016 inch stainless steel archwire to 4.6 degrees with a 0.018 × 0.025 inch stainless steel archwire. In a 0.022 inch stainless steel bracket slot, the engagement angle ranges from 18 degrees with a 0.018 × 0.025 inch stainless steel archwire to 6 degrees with a 0.021 × 0.025 inch stainless steel archwire. Active stainless steel self-ligating brackets demonstrate an engagement angle of approximately 7.5 degrees, whereas passive stainless steel self-ligating brackets show an engagement angle of approximately 14 degrees with 0.019 × 0.025 inch stainless steel wire in a 0.022 inch slot.Conclusions:The engagement angle depends on archwire dimension and edge shape, as well as on bracket slot dimension, and is variable and larger than published theoretical values. Clinically effective torque can be achieved in a 0.022 inch bracket slot with archwire torsion of 15 to 31 degrees for active self-ligating brackets and of 23 to 35 degrees for passive self-ligating brackets with a 0.019 × 0.025 inch stainless steel wire.     

In vitro evaluation of frictional force of a novel elastic bendable orthodontic wire

Objectives:To determine the frictional force (FF) of the novel, elastic, bendable titanium-niobium (Ti-Nb) alloy orthodontic wire in stainless steel (SS) brackets and to compare it with those of titanium-nickel (Ti-Ni) and titanium-molybdenum (Ti-Mo) alloy wires.Materials and Methods:Three sizes of Ti-Nb, Ti-Ni, and Ti-Mo alloy wires were ligated with elastic modules to 0.018-inch and 0.022-inch SS brackets. The dynamic FFs between the orthodontic wires and SS brackets were measured at three bracket-wire angles (0°, 5°, and 10°) with an Instron 5567 loading apparatus (Canton, Mass).Results:FFs increased gradually with the angle and wire size. In the 0.018-inch-slot bracket, the dynamic FFs of Ti-Nb and Ti-Ni alloy wires were almost the same, and those of the Ti-Mo alloy wire were significantly greater (P<0.05). FF values were 1.5–2 times greater in the 0.022-inch-slot bracket than in the 0.018-inch-slot bracket, regardless of alloy wire type, and the Ti-Mo alloy wire showed the greatest FF. Scanning electric microscopic images showed that the surface of the Ti-Mo alloy wire was much rougher than that of the Ti-Ni and Ti-Nb alloy wires.Conclusion:These findings demonstrate that the Ti-Nb alloy wire has almost the same frictional resistance as the Ti-Ni alloy wire, although it has a higher elastic modulus.     

Changes in physical properties of new,non-BPA containing,polymeric orthodontic bracket materials over time: A 2-year clinical study

PurposeThe purpose of this study was to develop new, biocompatible plastic brackets which are esthetic and do not release bisphenol A (BPA).Materials and methodsIn this study, brackets were fabricated using four different materials: polyacetal (POM), polyester (PE) and polycarbonate (PC), and a filled polycarbonate (PCF) as a control. Clinical testing using 46 subjects was conducted to evaluate changes in their physical properties (fracture frequency of bracket wings, strength of bracket wings and bracket wear) over 2 years (at baseline, year 1 and year 2) to assess the suitability of these materials for clinical use.Results(1) PE brackets were the only group that showed fracture in the fracture frequency test. (2) POM showed low wear rates. (3) POM showed great variation in bracket wing strength, but no statistical significant difference was observed between PE and POM.ConclusionThis 2-year clinical study concludes that POM and PE are more promising materials for the fabrication of orthodontic brackets than PCF.     

Pattern of stress distribution in different bracket–adhesive–tooth systems due to debonding load application

PurposeOrthodontic bracket debonding during treatment period is an unbecoming occurrence for both orthodontists and patients. Various clinical and numerical studies have been done to specify different parameters which affect the bond strength of bracket–adhesive–tooth system. Pattern of stress distribution seems to be an appropriate factor to estimate bond strength of different systems. Since it is not possible to experimentally define stress distribution in bracket–adhesive–tooth systems, three dimensional finite element method is used. The purpose of this study is to obtain and compare stress distribution of five bracket–adhesive–tooth systems with various enamel surface morphologies as an indicator parameter of these systems’ bond strength.Materials and methodsIn order to specify and compare stress in five different teeth, including maxillary central incisor, mandibular central incisor, maxillary canine, and maxillary and mandibular premolar, 3D STL files of teeth and brackets were reconstructed in MIMICS10 and were imported to HYPERMESH for each tooth, separately. Space between enamel and bracket was filled with orthodontic adhesive, mechanical property of each layer was assigned and appropriate boundary conditions were applied.ResultsIt was observed that stress distribution in bracket, adhesive and tooth due to shear load application had irregular pattern. For all of systems stress concentration was observed either on the borders or incisal and gingival regions of enamel–adhesive bonding region and adhesive layer.ConclusionDespite the overall similarity in stress distribution pattern of different bracket–adhesive–tooth systems, some differences on pattern of stress distribution and magnitude of stress were also observed. This may bring about more susceptibility of curved enamel surface teeth to lower bond strength, damage and fracture than flat enamel surface teeth.