可调式自锁托槽的摩擦力研究及有限元分析
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摘要
背景和目的
1935年,当第一种自锁托槽Russell Lock诞生的时候,并未引起正畸医师的广泛关注。发明者Jacob Stolzenberg医生认为自锁托槽具有减少复诊时间,病人感觉舒适,缩短正畸治疗总疗程等优点,但是由于Russell Lock自锁托槽结构相对简单,缺乏类似方丝弓托槽的双翼结构,没有得到其他正畸医生的认可,也最终没有成为一种被广泛应用的自锁托槽。20世纪70年代以后,随着正畸技术的发展,各种自锁托槽相继推出,例如：SPEED(Spring-loaded, Precision, Edgewise, Energy, Delivery)自锁托槽、Activa自锁托槽、Time自锁托槽、TwinLock自锁托槽、Damon SL、DamonⅡ自锁托槽、SmartClip自锁托槽和In-Ovation自锁托槽等。
以上各种类型的自锁托槽,大致可以根据滑盖或弹簧夹与托槽槽沟的接触形式分为两类：被动型和主动型。两类自锁托槽都具有的特点是：①不需要传统的不锈钢结扎丝或弹力橡胶圈；②利用托槽上可以开关的滑盖、弹簧夹,或是托槽自身的弹性结构,将矫治弓丝限定在托槽槽沟中；③操作便捷,节省椅旁操作时间,易于清洁。相对于传统直丝弓托槽,最新的自锁托槽不仅吸收了直丝弓托槽在正畸治疗中表现的大部分特点和能力,而且具备传统直丝弓托槽所没有的诸多优点。这一点大大推动了自锁托槽在正畸临床的广泛应用。美国正畸医生已经积累了十多年使用Damon系列自锁托槽的临床经验。2003年,由3M公司推出的Smartclip自锁托槽,因为结构简洁,使用方便,商业运作较为成功,也吸引了部分正畸医生将其应用到临床。
我国自上个世纪90年代就有使用加拿大SPEED自锁托槽的尝试。2000年之后,中国正畸医生们意识到自锁托槽的优势,逐渐开始学习引进并尝试在临床使用。在数年的临床应用过程中,不断的总结经验,探索自锁托槽的使用要点,论证其临床应用价值和前景。在使用自锁托槽的过程中,正畸医生们发现自锁托槽除了具有前述的优点,例如较轻的正畸矫治力,摩擦力较小,缩短矫治疗程之外,同样也有部分缺点,例如价格昂贵,矫治器对牙齿的三维控制能力下降,托槽结构相对复杂,容易损坏等。
在美国和欧洲,自锁托槽因为具有良好的经济前景,吸引了众多公司投入人力物力与正畸医生合作进行开发研究,取得了大量的成果和专利,并将其应用于临床。正畸器材的发展,离不开正畸医生,同样也离不开这些大公司的科研开发。自锁托槽成为继MBT直丝弓托槽之后,又一个正畸临床与商业运作成功结合的范例。
我国正畸医生使用的自锁托槽,大多数是国外公司的产品,价格比较昂贵。目前国内有关自锁托槽的知识产权比较少,不利于自锁托槽在我国的推广和应用,因此有必要在自锁托槽的设计上进行研究,为建立我国拥有自主知识产权的自锁托槽系统做初步探索。
本研究在总结常用的自锁托槽优缺点的基础上,设计了一种新型自锁托槽,并绘制了详细的图纸,制作了放大的托槽模型,对新托槽进行实验室研究。本研究分为两部分：第一部分,在实验室对新托槽模型进行体外摩擦力实验,研究在不同调节状态下,托槽对摩擦力的控制能力。第二部分,采用Pro/E软件对新托槽进行建模,运用三维有限元法对其进行分析,模拟口腔内的复杂力学环境,研究在不同受力状态下,托槽内部的应力变化状况,判断其在临床应用过程中的可靠性。
材料与方法
1.可调式自锁托槽的摩擦力研究
首先我们设计一种新型的自锁托槽,绘制详细的图纸,并申请了专利(专利号ZL200620084676.4)。
制作尺寸20倍的钢质托槽模型,同时制作尺寸20倍的钢质圆丝和方丝,直径分别为7.2mm、8.2mm、9.2mm的钢质圆丝(对应直径0.36mm、0.41 mm、0.46mm圆丝),以及9.2mm X 12.8mm(对应0.46mm X 0.64mm)和9.7×12.8mm(对应0.485mm X 0.64mm)的钢质方丝,弓丝长度均为400mm。由于普通钢与钢之间的摩擦系数与不锈钢相同,因此钢质的不同对实验结果的影响不大。
把新托槽模型固定在一个方槽内,以确保其不发生移动。方槽的两端放置两个定位器,以确保弓丝在托槽中处于无转矩、无倾斜的中央位置。将弓丝的端固定在拉力传感器上,传感器的另一端固定在电机的传动杆上,当电机和变速器开始拉动传动杆时,传感器把形变信号转化为电压信号并且传送到计算机内,计算机记录拉力的变化情况。开始实验前,调解定位器,使其与弓丝的接触是相切无压力状态,定位器的高度与托槽槽沟持平,然后,电机和变速器以2mm/min的速度拉动弓丝。
由于可调式装置可以通过旋转上升和下降,垫片与弓丝之间的位置可以发生变化。实验中垫片的位置分为四种状态：最高,与弓丝平面无压力状态相切,旋转0.5圈,旋转1圈。托槽槽沟无转矩,无轴倾角,弓丝处于槽沟的中央位置。由于有5种弓丝,分为4种状态,产生20种组合,每种组合测试10次。在测试前弓丝和托槽用95%酒精进行擦拭,避免油脂产生润滑作用。实验在室温24度,干燥状态下进行。每次更换弓丝时,同时更换托槽模型以避免磨损导致摩擦力下降。使用光学显微镜观察摩擦平面,以确认未发现明显的磨损。
摩擦力分为动摩擦力和静摩擦力两种情况,在记录的时候分开进行,弓丝开始运动时摩擦力的最大值作为静摩擦力数值,而弓丝开始稳定运动3mm以后数值作为动摩擦力。力值大小通过拉力传感器输入计算机,然后采用专用计算机软件进行处理。
数据结果采用SPSS11.0软件进行分析。
2.摩擦力可调式自锁托槽的三维有限元分析
首先选择进口的SUS304钢作为试验托槽的材料,确定SUS304的密度、维氏硬度、屈服强度、抗拉强度、延伸率、弹性模量、泊松比的指标。采用Pro/E软件定义单元类型、实常数、材料属性、网格尺寸,划分网格。本模型采用8节点六面体进行人工分网,分为320个节点,304个单元。
在托槽的近远中面进行固定约束,在托槽的上部结构中心从0°-180°加载200N的表面载荷,然后从托槽槽沟内部向托槽盖的中心0°-180°加载200N的表面载荷,在Ansys Workbench中进行求解分析,应用自锁托槽的Von Mises应力(Equivalent stress, EQV应力)峰值进行力学评估。
采用Ansys软件,对结果进行记录分析
结果
1.在垫片完全收入的状态下,7.2mm、8.2mm、9.2mm的钢圆丝(对应直径0.36mm、0.41mm、0.46mm圆丝),以及9.2mm X 12.8mm(对应0.46mm X 0.64mm)和9.7×12.8mm(对应0.485mm X 0.64mm)的不锈钢方丝的动静摩擦力均低于1N；垫片与弓丝无压力接触的状态时,所有弓丝的动、静摩擦力与前者无显著性差异；在继续旋转0.5圈之后,所有弓丝的动、静摩擦力与前两者之间有显著性差异(P<0.01)；旋转1圈之后,方丝的摩擦力过大,未能测量出结果,所有圆丝的动、静摩擦力与前三者之间有显著性差异(P<0.01)。
2.(1)当从不同角度对外部表面载荷加载过程中,模型应力分布情况比较相似。应力主要集中在轴的表面,盖与底座接合部位(开关处)。当外部载荷与模型X轴呈30°时,模型的应力峰值最大。
(2)当槽沟内部加载表面载荷的过程中,模型应力分布也比较相似,主要集中在轴的表面,垫片的下缘和盖与底座接合部位(开关处)。当表面载荷与模型X轴呈80°时,模型的应力峰值最大。
结论
1、可调式托槽通过上部调节装置的旋转,可以有效的调节摩擦力的大小,达到控制摩擦力大小的目的。
2、圆丝与方丝在托槽内滑动时,动、静摩擦力之间有显著差异,方丝大于圆丝。
3、当垫片位于完全收入的状态下或者垫片与弓丝相切时,弓丝与托槽的解除状态与Damon被动自锁托槽相似。
4、当可调式托槽在口内受到外部表面加载力时,轴的表面,盖与底座接合部位(开关处)是主要的应力集中区域,容易发生损坏；当外部载荷与模型X轴呈30°时,模型的应力峰值最大。
5、当槽沟内部加载表面载荷的过程中,轴的表面,垫片的下缘和盖与底座接合部位(开关处)是主要的应力集中区域。当表面载荷与模型X轴呈80°时,模型的应力峰值最大。
6、不论是外部加载还是内部加载表面负荷,其应力峰值均小于不锈钢的屈服系数,可调式托槽可以承受正常口腔内压力而不发生永久形变。
Background and Objective
In 1935, when the first self-ligating bracket--Russell Lock--born, it did not cause widespread concern in orthodontics doctors. Inventor Jacob Stolzenberg doctor regard the self-ligating bracket haveing lots of advantages, such as reduce referral, the patient feel comfortable, shorten the course of orthodontic treatment, and so on. However, because Russell Lock self-ligating bracket relatively simple structure, the lack of similar Edgewise bracket structure of the wings, and other orthodontic doctors have not been recognized, and eventually did not become a widely used by the self-ligating bracket.since the 1970's, with the development of orthodontic technology, all kinds of self-ligating bracket have been introduced, such as:SPEED (Spring-loaded, Precision, Edgewise, Energy, Delivery) self-ligating bracket, Activa self-ligating bracket, Time self-ligating bracket, TwinLock self-ligating bracket, Damon SL, DamonⅡself-ligating bracket, SmartClip self-ligating bracket and In-Ovation self-ligating bracket.
According to forms of slide contacting with brackets slots,above all types of self-lgating bracket generally can be divided into two categories:passive and active. Two kinds of self-ligating bracket all have the features:①eliminates the traditional stainless steel ligation wire or elastic rubber ring.②brackets can limit the treatment arch wire in bracket's slots by using active clip or passive slide.③operation convenient, time-saving operation next chair, and easy to clean. Compared with traditional straight wire bracket, the latest self-ligating brackets not only absorbed straight wire brackets in the orthodontic treatment in the majority of characteristics and performance capabilities, but with many advantages which traditional straight wire bracket does not have. This was greatly promoted the self-ligating bracket in a wide range of orthodontic clinical application. Orthodontic doctors with the United States for more than 10 years has been the use of self-ligating Damon Series Bracket clinical experience.2003,3 M Company introduced Smartclip self-ligating bracket, because simple, easy-to-use, the more successful commercial operation, and attract some of orthodontic doctors who will be its application to clinical practice.
In the 1990s, Miao Yaoqiang have used Canada SPEED Bracket attempt. After 2000, China orthodontic doctors aware of the self-ligating bracket advantages, gradually learning in the clinical introduction and try to use. In a few years the clinical application of the process of constantly sum up experience, and self-ligating bracket to explore the use of points, demonstrating its clinical value and prospects. In the use of self-ligating bracket in the process of orthodontic doctors found that self-ligating bracket addition to the aforementioned advantages, such as using light force in treatment, less friction and shorten treatment course. There are also some shortcomings, For example:expensive, dental appliance on the ability to control the three-dimensional drop brackets relatively complex structure, easy to damage.
In the United States and Europe, the self-ligating bracket because of good economic prospects, the company has attracted many resources into orthodontic doctors in cooperation with the Research and Development, made a lot of achievements and patents, and its clinical application. Development of self-ligating brackets can not be separated from orthodontic doctors, the same can not be separated from these big companies in research and development.
Self-ligating bracket became the successful combination of orthodontic clinical and commercial operation after the MBT straight wire bracket. The self-ligating bracket which China orthodontic doctors used is the majority of the foreign company's products and it's prices more expensive. At present the domestic self-ligating bracket of intellectual property rights less, to the detriment of self-ligating bracket in the promotion and application of our country, there is a need in the self-ligating bracket design study for the establishment of China's own self-ligating bracket knowledge property rights do preliminary exploration.
In conclusion of this study used self-ligating bracket on the basis of advantages and disadvantages, design a new type of self-ligating bracket, and the mapping of detailed drawings, produced an enlarged bracket model, the new brackets for laboratory research. This study is divided into two parts: the first part, in a laboratory model of the new brackets friction in vitro experiments on the regulation of different state, the friction brackets ability to control. The second part, with Pro/E software on the new brackets for modeling, using 3D finite element analysis method to simulate the complex mechanics of oral environment, the study of different state, the bracket changes in the internal stress, in the clinical judgement in the application of reliability.
Materials and Methods
1. Study of adjustable self-ligating bracket on the friction
First, we designed a new type of self-ligating bracket, drawing detailed drawings, And applied for a patent (Patent No:ZL200620084676.4)
Produced 20 times the size of the steel bracket model, and 20 times the size of the production of steel round wire and wire diameter of 7.2 mm,8.2mm,9.2mm steel round wire (corresponding diameter 0.36 mm,0.41mm,0.46mm round wire), and 9.2 mm x 12.8mm (for 0.46 mm x 0.64mm), and 9.7 x 12.8mm (corresponding 0.485 mm x 0.64mm) steel wire, each arch wire length is 400 mm. As ordinary steel and the friction coefficient between the same stainless steel,the steel of different little effect on the outcome of the experiment.
We welded the bracket in a square trough to make sure it will not move, and place two localizers at both ends of the square trough, which are to ensure that the arch wire has no torque and no tip in the bracket。Fasten one end of the sensor for pulling force on the archwire and the other end on the transmission shaft of the electrical machinery, so when the electrical machinery and the gears begin to pull the transmission shaft, the sensor will change the deformation signal into the voltage signal and send it to the compute that will record the changing conditions of the pulling force. Adjust the localizer before the experiment to make it touch the arc wire in a tangent and no pressure condition and its height level with the slot. The electrical machinery and the gears pull the archwire at a speed of 10mm/min. Ireland's study 13has proved that changing of the speed does not affect the magnitude of the frictional force remarkably when the speed of the transmission shaft goes from 0.5 to 50mm/min..
Since the FAS unit can up and down by revolving, the position of the shim and archwire can be changed accordingly. The positions of the shim in this experiment fall into four states:the highest, touching the wires in a no pressure and tangent condition, turning a half circle, and turning a whole circle. The slot of bracket in experiment has no tip and torque, wires was putted in center of the slot。Five kinds of wire and four states bring 20 combinations, and every one is tested 10 times. Clean the wires and the bracket with 95% alcohol before the experiment to avoid the lubrication of the greases. The experiment is conducted under a condition of 24℃inside and dryness. Clean the model of the bracket every time the wire is changed in case the abrasion causes the frictional force goes down. Therefore, use the magnifier to observe the frictional plane to confirm that no obvious abrasion occurs. Since the frictional force can be divided into the kinetic and the static, they are recorded respectively. The highest frictional force when the wire just starts to move is stated as the numerical value of the static, while the numerical value when the wire has moved steadily for 3mm is the kinetic。The values of the forces are put into the computer through the sensor, and then are processed by a special software. The SPSS 11.0 software is applied to conducting them statistic analysis.
2. The three-dimensional finite element analysis of adjustable self-ligating
bracket
First choosen imported steel SUS304 as the bracket material in experiment, determine the density of SUS304, Vickers hardness, yield strength, tensile strength, elongation, modulus of elasticity, Poisson's ratio, and other indicators. Used Pro/E software defined unit type, material properties, mesh size of the grid. This model uses the 8-node hexahedral artificial-net, divided into 320 nodes,304 units.
In brackets in the mesial-distal-fixed constraints, and in the structure of the upper bracket Centre from 0°-180°loading 200 N load on the surface and then from within the brackets plots to the center bracket covered 0°-180 N°200 loading on the surface load, carried out in the Ansys Workbench for analysis. Application of the self-ligating bracket Von Mises stress (Equivalent stress, stress EQV) peak mechanical assessment.
Ansys software used to record the results of experiment.
Results
1.In the result of this research, to the round wire, there is no significant difference on frictional force between state A and B, and obvious difference in statistics between states A、B and C、D (P<0.01) and difference in frictional forces between state C and D (P<0.01). To the square wires, the frictional force is too strong to be measured under state D, and there is no significant difference in frictional force between state A and B, but obvious difference in statistics between state A、BandC (P<0.01).
2.When from different angles on the external surface load loading process, the stress distribution model more similar. Mainly concentrated in the axial stress on the surface, cover and the base occupies a bit (switch). When the external load and model X-axis was 30 degrees, the largest peak stress model.When the trenches internal loading surface in the process of loading the model stress distribution is relatively similar, mainly concentrated in the shaft surface and the gasket and cover with the lower edge of the base interface (switch). When the load and surface model X-axis was 80 degrees, the largest peak stress model.
Conclusions
1 Round wire and wire care bed in the slide, dynamic and static friction between the significant difference, more than round wire to wire.
2 When the gasket in the A, B status, arch wire and brackets contact state and Damon passive self-ligating bracket similar.
3 Adjustable upper bracket adjustment device through the rotation, can effectively adjust the size of friction, the friction to control purposes.
4 When the adjustable brackets in the mouth by the external surface of the load, the surface shaft, covered with the base occupies a bit (switch) is a major stress on the regional, easily damaged when the external load and a 30 model X-axis degrees, the largest peak stress model.
5 When plots internal loading surface in the process of loading, mainly concentrated in the shaft surface and the gasket and cover with the lower edge of the base interface (switch) is a major stress on the region. When the load and surface model X-axis was 80 degrees, the largest peak stress model.
6 Whether external or internal loading loading surface load, the stress peaks were less than the yield coefficient of stainless steel, adjustable brackets can withstand the pressure instead of the normal oral permanent deformation occurred.
1935年,当第一种自锁托槽Russell Lock诞生的时候,并未引起正畸医师的广泛关注。发明者Jacob Stolzenberg医生认为自锁托槽具有减少复诊时间,病人感觉舒适,缩短正畸治疗总疗程等优点,但是由于Russell Lock自锁托槽结构相对简单,缺乏类似方丝弓托槽的双翼结构,没有得到其他正畸医生的认可,也最终没有成为一种被广泛应用的自锁托槽。20世纪70年代以后,随着正畸技术的发展,各种自锁托槽相继推出,例如：SPEED(Spring-loaded, Precision, Edgewise, Energy, Delivery)自锁托槽、Activa自锁托槽、Time自锁托槽、TwinLock自锁托槽、Damon SL、DamonⅡ自锁托槽、SmartClip自锁托槽和In-Ovation自锁托槽等。
以上各种类型的自锁托槽,大致可以根据滑盖或弹簧夹与托槽槽沟的接触形式分为两类：被动型和主动型。两类自锁托槽都具有的特点是：①不需要传统的不锈钢结扎丝或弹力橡胶圈；②利用托槽上可以开关的滑盖、弹簧夹,或是托槽自身的弹性结构,将矫治弓丝限定在托槽槽沟中；③操作便捷,节省椅旁操作时间,易于清洁。相对于传统直丝弓托槽,最新的自锁托槽不仅吸收了直丝弓托槽在正畸治疗中表现的大部分特点和能力,而且具备传统直丝弓托槽所没有的诸多优点。这一点大大推动了自锁托槽在正畸临床的广泛应用。美国正畸医生已经积累了十多年使用Damon系列自锁托槽的临床经验。2003年,由3M公司推出的Smartclip自锁托槽,因为结构简洁,使用方便,商业运作较为成功,也吸引了部分正畸医生将其应用到临床。
我国自上个世纪90年代就有使用加拿大SPEED自锁托槽的尝试。2000年之后,中国正畸医生们意识到自锁托槽的优势,逐渐开始学习引进并尝试在临床使用。在数年的临床应用过程中,不断的总结经验,探索自锁托槽的使用要点,论证其临床应用价值和前景。在使用自锁托槽的过程中,正畸医生们发现自锁托槽除了具有前述的优点,例如较轻的正畸矫治力,摩擦力较小,缩短矫治疗程之外,同样也有部分缺点,例如价格昂贵,矫治器对牙齿的三维控制能力下降,托槽结构相对复杂,容易损坏等。
在美国和欧洲,自锁托槽因为具有良好的经济前景,吸引了众多公司投入人力物力与正畸医生合作进行开发研究,取得了大量的成果和专利,并将其应用于临床。正畸器材的发展,离不开正畸医生,同样也离不开这些大公司的科研开发。自锁托槽成为继MBT直丝弓托槽之后,又一个正畸临床与商业运作成功结合的范例。
我国正畸医生使用的自锁托槽,大多数是国外公司的产品,价格比较昂贵。目前国内有关自锁托槽的知识产权比较少,不利于自锁托槽在我国的推广和应用,因此有必要在自锁托槽的设计上进行研究,为建立我国拥有自主知识产权的自锁托槽系统做初步探索。
本研究在总结常用的自锁托槽优缺点的基础上,设计了一种新型自锁托槽,并绘制了详细的图纸,制作了放大的托槽模型,对新托槽进行实验室研究。本研究分为两部分：第一部分,在实验室对新托槽模型进行体外摩擦力实验,研究在不同调节状态下,托槽对摩擦力的控制能力。第二部分,采用Pro/E软件对新托槽进行建模,运用三维有限元法对其进行分析,模拟口腔内的复杂力学环境,研究在不同受力状态下,托槽内部的应力变化状况,判断其在临床应用过程中的可靠性。
材料与方法
1.可调式自锁托槽的摩擦力研究
首先我们设计一种新型的自锁托槽,绘制详细的图纸,并申请了专利(专利号ZL200620084676.4)。
制作尺寸20倍的钢质托槽模型,同时制作尺寸20倍的钢质圆丝和方丝,直径分别为7.2mm、8.2mm、9.2mm的钢质圆丝(对应直径0.36mm、0.41 mm、0.46mm圆丝),以及9.2mm X 12.8mm(对应0.46mm X 0.64mm)和9.7×12.8mm(对应0.485mm X 0.64mm)的钢质方丝,弓丝长度均为400mm。由于普通钢与钢之间的摩擦系数与不锈钢相同,因此钢质的不同对实验结果的影响不大。
把新托槽模型固定在一个方槽内,以确保其不发生移动。方槽的两端放置两个定位器,以确保弓丝在托槽中处于无转矩、无倾斜的中央位置。将弓丝的端固定在拉力传感器上,传感器的另一端固定在电机的传动杆上,当电机和变速器开始拉动传动杆时,传感器把形变信号转化为电压信号并且传送到计算机内,计算机记录拉力的变化情况。开始实验前,调解定位器,使其与弓丝的接触是相切无压力状态,定位器的高度与托槽槽沟持平,然后,电机和变速器以2mm/min的速度拉动弓丝。
由于可调式装置可以通过旋转上升和下降,垫片与弓丝之间的位置可以发生变化。实验中垫片的位置分为四种状态：最高,与弓丝平面无压力状态相切,旋转0.5圈,旋转1圈。托槽槽沟无转矩,无轴倾角,弓丝处于槽沟的中央位置。由于有5种弓丝,分为4种状态,产生20种组合,每种组合测试10次。在测试前弓丝和托槽用95%酒精进行擦拭,避免油脂产生润滑作用。实验在室温24度,干燥状态下进行。每次更换弓丝时,同时更换托槽模型以避免磨损导致摩擦力下降。使用光学显微镜观察摩擦平面,以确认未发现明显的磨损。
摩擦力分为动摩擦力和静摩擦力两种情况,在记录的时候分开进行,弓丝开始运动时摩擦力的最大值作为静摩擦力数值,而弓丝开始稳定运动3mm以后数值作为动摩擦力。力值大小通过拉力传感器输入计算机,然后采用专用计算机软件进行处理。
数据结果采用SPSS11.0软件进行分析。
2.摩擦力可调式自锁托槽的三维有限元分析
首先选择进口的SUS304钢作为试验托槽的材料,确定SUS304的密度、维氏硬度、屈服强度、抗拉强度、延伸率、弹性模量、泊松比的指标。采用Pro/E软件定义单元类型、实常数、材料属性、网格尺寸,划分网格。本模型采用8节点六面体进行人工分网,分为320个节点,304个单元。
在托槽的近远中面进行固定约束,在托槽的上部结构中心从0°-180°加载200N的表面载荷,然后从托槽槽沟内部向托槽盖的中心0°-180°加载200N的表面载荷,在Ansys Workbench中进行求解分析,应用自锁托槽的Von Mises应力(Equivalent stress, EQV应力)峰值进行力学评估。
采用Ansys软件,对结果进行记录分析
结果
1.在垫片完全收入的状态下,7.2mm、8.2mm、9.2mm的钢圆丝(对应直径0.36mm、0.41mm、0.46mm圆丝),以及9.2mm X 12.8mm(对应0.46mm X 0.64mm)和9.7×12.8mm(对应0.485mm X 0.64mm)的不锈钢方丝的动静摩擦力均低于1N；垫片与弓丝无压力接触的状态时,所有弓丝的动、静摩擦力与前者无显著性差异；在继续旋转0.5圈之后,所有弓丝的动、静摩擦力与前两者之间有显著性差异(P<0.01)；旋转1圈之后,方丝的摩擦力过大,未能测量出结果,所有圆丝的动、静摩擦力与前三者之间有显著性差异(P<0.01)。
2.(1)当从不同角度对外部表面载荷加载过程中,模型应力分布情况比较相似。应力主要集中在轴的表面,盖与底座接合部位(开关处)。当外部载荷与模型X轴呈30°时,模型的应力峰值最大。
(2)当槽沟内部加载表面载荷的过程中,模型应力分布也比较相似,主要集中在轴的表面,垫片的下缘和盖与底座接合部位(开关处)。当表面载荷与模型X轴呈80°时,模型的应力峰值最大。
结论
1、可调式托槽通过上部调节装置的旋转,可以有效的调节摩擦力的大小,达到控制摩擦力大小的目的。
2、圆丝与方丝在托槽内滑动时,动、静摩擦力之间有显著差异,方丝大于圆丝。
3、当垫片位于完全收入的状态下或者垫片与弓丝相切时,弓丝与托槽的解除状态与Damon被动自锁托槽相似。
4、当可调式托槽在口内受到外部表面加载力时,轴的表面,盖与底座接合部位(开关处)是主要的应力集中区域,容易发生损坏；当外部载荷与模型X轴呈30°时,模型的应力峰值最大。
5、当槽沟内部加载表面载荷的过程中,轴的表面,垫片的下缘和盖与底座接合部位(开关处)是主要的应力集中区域。当表面载荷与模型X轴呈80°时,模型的应力峰值最大。
6、不论是外部加载还是内部加载表面负荷,其应力峰值均小于不锈钢的屈服系数,可调式托槽可以承受正常口腔内压力而不发生永久形变。
Background and Objective
In 1935, when the first self-ligating bracket--Russell Lock--born, it did not cause widespread concern in orthodontics doctors. Inventor Jacob Stolzenberg doctor regard the self-ligating bracket haveing lots of advantages, such as reduce referral, the patient feel comfortable, shorten the course of orthodontic treatment, and so on. However, because Russell Lock self-ligating bracket relatively simple structure, the lack of similar Edgewise bracket structure of the wings, and other orthodontic doctors have not been recognized, and eventually did not become a widely used by the self-ligating bracket.since the 1970's, with the development of orthodontic technology, all kinds of self-ligating bracket have been introduced, such as:SPEED (Spring-loaded, Precision, Edgewise, Energy, Delivery) self-ligating bracket, Activa self-ligating bracket, Time self-ligating bracket, TwinLock self-ligating bracket, Damon SL, DamonⅡself-ligating bracket, SmartClip self-ligating bracket and In-Ovation self-ligating bracket.
According to forms of slide contacting with brackets slots,above all types of self-lgating bracket generally can be divided into two categories:passive and active. Two kinds of self-ligating bracket all have the features:①eliminates the traditional stainless steel ligation wire or elastic rubber ring.②brackets can limit the treatment arch wire in bracket's slots by using active clip or passive slide.③operation convenient, time-saving operation next chair, and easy to clean. Compared with traditional straight wire bracket, the latest self-ligating brackets not only absorbed straight wire brackets in the orthodontic treatment in the majority of characteristics and performance capabilities, but with many advantages which traditional straight wire bracket does not have. This was greatly promoted the self-ligating bracket in a wide range of orthodontic clinical application. Orthodontic doctors with the United States for more than 10 years has been the use of self-ligating Damon Series Bracket clinical experience.2003,3 M Company introduced Smartclip self-ligating bracket, because simple, easy-to-use, the more successful commercial operation, and attract some of orthodontic doctors who will be its application to clinical practice.
In the 1990s, Miao Yaoqiang have used Canada SPEED Bracket attempt. After 2000, China orthodontic doctors aware of the self-ligating bracket advantages, gradually learning in the clinical introduction and try to use. In a few years the clinical application of the process of constantly sum up experience, and self-ligating bracket to explore the use of points, demonstrating its clinical value and prospects. In the use of self-ligating bracket in the process of orthodontic doctors found that self-ligating bracket addition to the aforementioned advantages, such as using light force in treatment, less friction and shorten treatment course. There are also some shortcomings, For example:expensive, dental appliance on the ability to control the three-dimensional drop brackets relatively complex structure, easy to damage.
In the United States and Europe, the self-ligating bracket because of good economic prospects, the company has attracted many resources into orthodontic doctors in cooperation with the Research and Development, made a lot of achievements and patents, and its clinical application. Development of self-ligating brackets can not be separated from orthodontic doctors, the same can not be separated from these big companies in research and development.
Self-ligating bracket became the successful combination of orthodontic clinical and commercial operation after the MBT straight wire bracket. The self-ligating bracket which China orthodontic doctors used is the majority of the foreign company's products and it's prices more expensive. At present the domestic self-ligating bracket of intellectual property rights less, to the detriment of self-ligating bracket in the promotion and application of our country, there is a need in the self-ligating bracket design study for the establishment of China's own self-ligating bracket knowledge property rights do preliminary exploration.
In conclusion of this study used self-ligating bracket on the basis of advantages and disadvantages, design a new type of self-ligating bracket, and the mapping of detailed drawings, produced an enlarged bracket model, the new brackets for laboratory research. This study is divided into two parts: the first part, in a laboratory model of the new brackets friction in vitro experiments on the regulation of different state, the friction brackets ability to control. The second part, with Pro/E software on the new brackets for modeling, using 3D finite element analysis method to simulate the complex mechanics of oral environment, the study of different state, the bracket changes in the internal stress, in the clinical judgement in the application of reliability.
Materials and Methods
1. Study of adjustable self-ligating bracket on the friction
First, we designed a new type of self-ligating bracket, drawing detailed drawings, And applied for a patent (Patent No:ZL200620084676.4)
Produced 20 times the size of the steel bracket model, and 20 times the size of the production of steel round wire and wire diameter of 7.2 mm,8.2mm,9.2mm steel round wire (corresponding diameter 0.36 mm,0.41mm,0.46mm round wire), and 9.2 mm x 12.8mm (for 0.46 mm x 0.64mm), and 9.7 x 12.8mm (corresponding 0.485 mm x 0.64mm) steel wire, each arch wire length is 400 mm. As ordinary steel and the friction coefficient between the same stainless steel,the steel of different little effect on the outcome of the experiment.
We welded the bracket in a square trough to make sure it will not move, and place two localizers at both ends of the square trough, which are to ensure that the arch wire has no torque and no tip in the bracket。Fasten one end of the sensor for pulling force on the archwire and the other end on the transmission shaft of the electrical machinery, so when the electrical machinery and the gears begin to pull the transmission shaft, the sensor will change the deformation signal into the voltage signal and send it to the compute that will record the changing conditions of the pulling force. Adjust the localizer before the experiment to make it touch the arc wire in a tangent and no pressure condition and its height level with the slot. The electrical machinery and the gears pull the archwire at a speed of 10mm/min. Ireland's study 13has proved that changing of the speed does not affect the magnitude of the frictional force remarkably when the speed of the transmission shaft goes from 0.5 to 50mm/min..
Since the FAS unit can up and down by revolving, the position of the shim and archwire can be changed accordingly. The positions of the shim in this experiment fall into four states:the highest, touching the wires in a no pressure and tangent condition, turning a half circle, and turning a whole circle. The slot of bracket in experiment has no tip and torque, wires was putted in center of the slot。Five kinds of wire and four states bring 20 combinations, and every one is tested 10 times. Clean the wires and the bracket with 95% alcohol before the experiment to avoid the lubrication of the greases. The experiment is conducted under a condition of 24℃inside and dryness. Clean the model of the bracket every time the wire is changed in case the abrasion causes the frictional force goes down. Therefore, use the magnifier to observe the frictional plane to confirm that no obvious abrasion occurs. Since the frictional force can be divided into the kinetic and the static, they are recorded respectively. The highest frictional force when the wire just starts to move is stated as the numerical value of the static, while the numerical value when the wire has moved steadily for 3mm is the kinetic。The values of the forces are put into the computer through the sensor, and then are processed by a special software. The SPSS 11.0 software is applied to conducting them statistic analysis.
2. The three-dimensional finite element analysis of adjustable self-ligating
bracket
First choosen imported steel SUS304 as the bracket material in experiment, determine the density of SUS304, Vickers hardness, yield strength, tensile strength, elongation, modulus of elasticity, Poisson's ratio, and other indicators. Used Pro/E software defined unit type, material properties, mesh size of the grid. This model uses the 8-node hexahedral artificial-net, divided into 320 nodes,304 units.
In brackets in the mesial-distal-fixed constraints, and in the structure of the upper bracket Centre from 0°-180°loading 200 N load on the surface and then from within the brackets plots to the center bracket covered 0°-180 N°200 loading on the surface load, carried out in the Ansys Workbench for analysis. Application of the self-ligating bracket Von Mises stress (Equivalent stress, stress EQV) peak mechanical assessment.
Ansys software used to record the results of experiment.
Results
1.In the result of this research, to the round wire, there is no significant difference on frictional force between state A and B, and obvious difference in statistics between states A、B and C、D (P<0.01) and difference in frictional forces between state C and D (P<0.01). To the square wires, the frictional force is too strong to be measured under state D, and there is no significant difference in frictional force between state A and B, but obvious difference in statistics between state A、BandC (P<0.01).
2.When from different angles on the external surface load loading process, the stress distribution model more similar. Mainly concentrated in the axial stress on the surface, cover and the base occupies a bit (switch). When the external load and model X-axis was 30 degrees, the largest peak stress model.When the trenches internal loading surface in the process of loading the model stress distribution is relatively similar, mainly concentrated in the shaft surface and the gasket and cover with the lower edge of the base interface (switch). When the load and surface model X-axis was 80 degrees, the largest peak stress model.
Conclusions
1 Round wire and wire care bed in the slide, dynamic and static friction between the significant difference, more than round wire to wire.
2 When the gasket in the A, B status, arch wire and brackets contact state and Damon passive self-ligating bracket similar.
3 Adjustable upper bracket adjustment device through the rotation, can effectively adjust the size of friction, the friction to control purposes.
4 When the adjustable brackets in the mouth by the external surface of the load, the surface shaft, covered with the base occupies a bit (switch) is a major stress on the regional, easily damaged when the external load and a 30 model X-axis degrees, the largest peak stress model.
5 When plots internal loading surface in the process of loading, mainly concentrated in the shaft surface and the gasket and cover with the lower edge of the base interface (switch) is a major stress on the region. When the load and surface model X-axis was 80 degrees, the largest peak stress model.
6 Whether external or internal loading loading surface load, the stress peaks were less than the yield coefficient of stainless steel, adjustable brackets can withstand the pressure instead of the normal oral permanent deformation occurred.
引文
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[4]Thorstenson GA, Kusy RP. Comparison of resistance to sliding between different self-ligating brackets with second-order angulation in the dry and saliva states[J]. Am J Orthod Dentofacial Orthop,2002,121(4):472-482.
[5]Thorstenson GA, Kusy RP. Effect of archwire size and material on the resistance to sliding of self-ligating brackets with second order angnlation in the dry state [J]. Am J Orthod Dentofacial Orthop,2002,122(2):295-305.
[6]Caeeiafesta V, Sfondrini MF, Rieciardi A, et al. Evaluation of friction of stainless steel and esthetic self-ligating brackets in various bracket-archwire combinations [J]. Am J Orthod Dentofacial Orthop,2003,124(4):395-402.
[7]Voudouris JC. Interactive edgewise mechanisms: form and function comparison with conventional edgewise brackets. Am J Orthod Dentofac Orthop 1997; 111:119-140.
[8]Henao SP, Kusy RP. Frictional evaluations of dental typodont models using four self-ligating designs and a conventional design[J]. Angle Orthop,2004, 75(1):75—78.
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[11]Griffiths HS, Sherriff M, Ireland AJ. Resistance to sliding with 3 types of elastomeric modules [J]. Am J Orthod Dentofacial Orthop,2005,127(5): 670-675.
[12]Tecco S, Festa F, Caputi S, et al. Friction of conventional and self-Ligating brackets using a 10 bracket model[J]. Angle Orthod.2005.75(6): 1041-1045.
[13]O'Reilly D, Dowling PA, Lagerstrom L, Swartz ML.An ex-vivo investigation into the effect of bracket displacement on resistance to sliding[J]. Br J Orthod 1999; 26:219-227.
[14]Pilon JGM, Kuijpers-Jagtman AM, Maltha JC. Magnitude of orthodontic forces and rate of bodily tooth movement. An experimental study. Am J Orthod Dentofac Orthop 1996; 110:16-23.
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[1]姜若萍,傅明魁.自锁托槽的特点及其临床应用[J].口腔正畸学.2006.13(4)：187—190.
[2]Henao SP,Kusy RP. Evaluation of the frictional resistance of conventional and self-ligating bracket designs using standardized archwires and dental typodonts [J]. Angle Orthod,2004 74(2):202-211.
[3]Meling T R, Odegaard J, Holthe Ko et al. Am J Orthod Dentofacial Orthop, 1997,112(1):41-49.
[4]Thorstenson GA, Kusy RP. Comparison of resistance to sliding between different self-ligating brackets with second-order angulation in the dry and saliva states[J]. Am J Orthod Dentofacial Orthop,2002,121(4):472-482.
[5]Thorstenson GA, Kusy RP. Effect of archwire size and material on the resistance to sliding of self-ligating brackets with second order angnlation in the dry state [J]. Am J Orthod Dentofacial Orthop,2002,122(2):295-305.
[6]Caeeiafesta V, Sfondrini MF, Rieciardi A, et al. Evaluation of friction of stainless steel and esthetic self-ligating brackets in various bracket-archwire combinations [J]. Am J Orthod Dentofacial Orthop,2003,124(4):395-402.
[7]Voudouris JC. Interactive edgewise mechanisms: form and function comparison with conventional edgewise brackets. Am J Orthod Dentofac Orthop 1997; 111:119-140.
[8]Henao SP, Kusy RP. Frictional evaluations of dental typodont models using four self-ligating designs and a conventional design[J]. Angle Orthop,2004, 75(1):75—78.
[9]Harradine NWT. The clinical use of Activa self-ligating brackets[J]. Am J Orthod Dentofacial Orthop,1996,109(3):319—328.
[10]Read-Ward GE, Jones SP, Davies EH. A comparison of self-ligating and conventional orthodontic bracket systems[J]. Br J Orthod,1997,24(3): 309-317.
[11]Griffiths HS, Sherriff M, Ireland AJ. Resistance to sliding with 3 types of elastomeric modules [J]. Am J Orthod Dentofacial Orthop,2005,127(5): 670-675.
[12]Tecco S, Festa F, Caputi S, et al. Friction of conventional and self-Ligating brackets using a 10 bracket model[J]. Angle Orthod.2005.75(6): 1041-1045.
[13]O'Reilly D, Dowling PA, Lagerstrom L, Swartz ML.An ex-vivo investigation into the effect of bracket displacement on resistance to sliding[J]. Br J Orthod 1999; 26:219-227.
[14]Pilon JGM, Kuijpers-Jagtman AM, Maltha JC. Magnitude of orthodontic forces and rate of bodily tooth movement. An experimental study. Am J Orthod Dentofac Orthop 1996; 110:16-23.
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