【作者】 黄世友；

【导师】 段银钟； 刁东风；

【作者基本信息】 第四军医大学 ， 口腔临床医学， 2013， 博士

【摘要】 研究目的不锈钢、镍钛合金作为正畸托槽及弓丝的制造材料已经应用多年，但这些合金表面耐磨性差，摩擦系数高，易被氟化物腐蚀并析出离子，这些缺点可通过表面处理技术加以改善。类金刚石（DLC）膜具有良好的生物相容性和优异的摩擦学性能，是理想的生物涂层材料，其在工业领域的应用研究已广泛开展，在生物医学领域的临床研究也获得了重大进展。本课题拟通过在正畸托槽及弓丝表面研制类金刚石膜，并评估类金刚石膜对正畸托槽-弓丝表面生物学行为及摩擦磨损性能的影响，从而为类金刚石膜改性技术在口腔正畸领域应用提供实验依据。研究方法1.采用封闭式电子回旋共振（MCECR）等离子体溅射技术在正畸不锈钢（316Lstainless steel）表面制备类金刚石膜，利用Pin-on-Disk标准摩擦磨损试验机研究薄膜的摩擦磨损性能，以寻找在托槽、弓丝上制备类金刚石膜的最佳镀膜工艺参数。2.选用变形链球菌（S. mutans）在DLC薄膜表面进行细菌粘附对比试验，以及人牙周膜细胞（HPDLC）在DLC薄膜表面进行细胞粘附、增殖对比试验（MTT比色实验），以测试DLC薄膜的抗菌性能和生物安全性。3.设计、建造口腔正畸微振动摩擦磨损测试系统，模拟正畸牙移动方式，以及托槽-弓丝接触的扭转、转矩变化，以测试托槽-弓丝间动态摩擦力。4.在正畸镍钛弓丝表面制备类金刚石膜，对镀膜弓丝及传统弓丝在含氟环境下抗腐蚀及摩擦磨损性能进行比较研究。5.在不锈钢托槽及弓丝表面制备类金刚石膜，利用自主研发的正畸微振动试验机，测试托槽-弓丝间的摩擦行为。测试运行参数设置为：载荷1N，频率0.5Hz，位移振幅±150μm。表面制备类金刚石膜的托槽、弓丝和传统的托槽、弓丝组成多种摩擦组合，分别在干燥环境和人工唾液环境条件下进行了摩擦磨损性能的测试。采用扫描电子显微镜（SEM）对测试后托槽及弓丝表面磨痕进行观察分析。研究结果1.与无膜不锈钢相比较，表面制备类金刚石膜的316L不锈钢摩擦系数明显降低，薄膜平均磨损寿命达8000圈，表现出优异的摩擦磨损性能。2.人牙周膜细胞在类金刚石膜表面生长情况好于不锈钢表面，细胞更扁平，铺展更好，类金刚石薄膜表面对人牙周膜细胞表现出更好的生物相容性；此外，与不锈钢表面相比较，变形链球菌在类金刚石膜表面粘附和增殖明显减少。3.成功研发了一套正畸微振动摩擦磨损测试系统，可以在一定程度上模拟复杂的托槽-弓丝接触状况，进行正畸摩擦力的体外实验研究。4.与传统弓丝比较，制备类金刚石膜的镍钛弓丝在高氟离子环境中浸泡后表面粗糙度无明显改变，证实了类金刚石膜优异的抗腐蚀性能。摩擦试验结果显示，无论在干燥环境或人工唾液环境，类金刚石膜明显降低了托槽-弓丝间摩擦系数，减轻了磨损。5.无论在干燥或人工唾液环境下，与传统弓丝比较，制备类金刚石膜的不锈钢弓丝明显降低了托槽-弓丝间摩擦系数；但制备类金刚石膜的不锈钢托槽并没有降低托槽-弓丝间摩擦系数。显微照片分析可知，类金刚石膜明显减轻了弓丝表面的接触磨损，同时，显微照片也显示了托槽槽沟边沿存在明显的不规则嵴状突起等加工缺陷，这些应力集中区的嵴状突起使其在摩擦接触时无法形成摩擦转移膜，因而类金刚石膜在此无法起到降低托槽摩擦力及减轻磨损的作用。结论1.在正畸不锈钢表面成功制备了类金刚石膜，类金刚石膜对人牙周膜细胞具有良好生物相容性，并表现出抵抗变形链球菌粘附的能力，是理想的生物医学材料。2.正畸微振动摩擦测试系统的成功研发，为精确测量托槽-弓丝间摩擦力提供了测试手段。3.类金刚石膜推荐作为镍钛弓丝的涂层材料，可提高弓丝在含氟环境中的抗腐蚀能力并改善摩擦性能。4.不锈钢弓丝表面制备类金刚石膜可明显降低摩擦系数并减轻磨损；然而，在目前的托槽表面制备类金刚石膜并不能改善托槽的摩擦性能，托槽槽沟边沿需改善设计及加工工艺。总之，具有良好生物相容性和优异物理化学性能的类金刚石膜将广泛应用于口腔生物医学领域。更多还原

【Abstract】 ObjectiveStainless steel and Nickel-titanium (NiTi) alloys have been applied in orthodontictreatment for several decades due to their biocompatibility and mechanical properties.Nevertheless, they are still controversial in long-term clinical applications because of thehigh friction coefficient and the decreasing of corrosion resistance in active saliva orfluoride solutions. The long-term biocompatibility and frictional characteristics can beimproved by using various surface modification methods. Diamond-like carbon (DLC)films are very promising candidates for this bio-application owing to their good biocompatibility and tribological properties, and it has been widely expected to be adaptedas new biocompatible coatings. The purpose of this study was to investigate the potentialinterest in DLC coating for applying to orthodontic appliances. Hence DLC films weredeposited on orthodontic archwires and brackets, and an in vitro biological andtribological evaluation was carried out.Methods1. DLC films were prepared on the surfaces of316L stainless steel byMirror-Confinement-type Electron Cyclotron Resonance (MCECR) plasma sputteringtechnique, and the friction behaviour and abrasion performance of DLC films wereinvestigated using a Pin-on-Disk friction and wear tester.2. The bacterial adhesion and antibacterial property of the DLC coating wasevaluated against streptococcus mutans MS95051. Cell behavior of human periodontalligament fibroblasts was evaluated in terms of cell adhesion on the DLC films, cellviability/proliferation (MTT assay) and pattern of cell growth.3. We developed a specific fretting test which permitted the micro-slidings tosimulate tooth movement. The fretting machine is very promising for investigatingbracket-to-wire angulation and rotation, studying environmental conditions, and thefrequency of the oscillation, as well as other parameters that could have tribologicaleffects.4. DLC films were deposited on Ni-Ti orthodontic archwires, and the influences of afluoride-containing environment on the surface topography and the friction coefficientbetween brackets and archwires were subsequently investigated.5. DLC films were deposited on the stainless steel brackets and archwires. Thetribological behavior of archwire-bracket contacts was investigated at a normal load of1Nand a frequency of0.5Hz for displacement amplitude of±150μm. Variousarchwire-bracket combinations were investigated under dry and artificial saliva conditions.After fretting tests the surface morphology of archwires and brackets were analyzed byusing scanning electron microscopy (SEM). Results1. DLC films were deposited on stainless steel, and the results of frictional testsshowed that the samples coated by DLC films exhibited lower and more stable frictioncoefficient than that of uncoated samples. The mean abrasion life of carbon film reached avalue of8000cycle.2. The study examined the biological behavior of human periodontal ligamentfibroblasts on the DLC-coated surface. The results demonstrated that DLC-caoted surfacewell supported the growth, spreading, attachment and proliferation of cell. Meanwhile, theSEM images as well as the counting results of bacterium revealed that the multiplicationof streptococcus mutans was not obvious on the DLC-coated surfaces than on theuncoated surface.3. A specific fretting apparatus consisting of reciprocating tangential displacementswas developed to study the tribological behavior of archwire-bracket contacts.4. The results confirmed the superior nature of the DLC coating, evident as fewersurface roughness variation for DLC-coated Ni-Ti archwires after immersion in a highfluoride ion environment. Moreover, the friction tests shown that the application of DLCcoating significantly decreased the fretting wear and the coefficient of friction both inambient air and artificial saliva.5. The DLC-coated stainless steel wires showed significantly lower frictioncoefficient than the uncoated wires independently of the applied environments.Nevertheless, the DLC-coated and uncoated brackets showed no significant differences inthe friction coefficient. Microscopic analysis showed that low wear took place for theDLC-coated surfaces. In addition, the dominant defect caused by mechanical treatmentduring manufacturing process was especially seen on the external edges of the bracket slotbottom surface. The debris of DLC layer could not remain on such ridged contact surfaceand form a transfer film, which favored the lubrication of the interface of wire-bracketcoupling.Conclusions 1. The MCECR deposition technique allows the growth of dense, homogeneous DLCcoatings on stainless steel substrates. DLC coatings provide a suitable surface for cellattachment, spreading and proliferation, further suggesting the lack of cytotoxicity of thiscoating. In addition, the antibacterial tests show that DLC films exhibit antibacterialproperties.2. The fretting machine appears suitable for evaluating the frictional behavior oforthodontic bracket-wire combinations because of its controllable test parameters, such ascontact configuration and positioning. It permits standardizing the testing methods andachieving reproducible findings.3. DLC coating is recommended in order to reduce the fluoride-induced corrosionand improve the orthodontic friction for Ni-Ti archwires.4. The application of DLC coating on archwires significantly decreases theorthodontic fretting wear and coefficient of friction. Unfortunately it does not affect thefrictional properties for brackets at present, and the design, production techniques andfinal polishing process of the bracket slot bottom should be improved.In a word, the cellular biocompatibility of the DLC coatings, allied with the excellentphysico-chemical performance, anticipates a wide range of applications in the dentalbiomedical field.更多还原