The mechanism of synergistic effect between wear and microbe corrosion in the degradation process of dental materials

本研究的目的是开发测试方法，以评估暴露在口腔中的牙齿材料在微生物腐蚀和牙齿碰撞引起的机械力的共同作用下的性能。动态磨损条件的测定：利用载荷传感器（Tekscan）测定牙齿在咀嚼软质或硬质食物时产生的应力，获得最大载荷的程度、加载速度和接触时间，范围分别为4-13 kgf、0.03-0.07 kgf/ms、420-500 ms。2 .牙体材料的降解过程及降解指标：选取牙体高度降低引起的牙体不良，选择牙体高度降低作为降解指标。试验方法的发展：对于金属材料，采用平板（试样）与球体（Al_2O_3）相结合的方法模拟齿间相遇。通过球体对试样反复施加载荷，使试样表面产生压痕，压痕的直径与压痕的深度成正比，即齿高的减小。随着试验时间的延长，其随加载频率的增加呈指数函数关系，这与位错的延迟运动有一定关系。结果表明，在3% NaCl溶液中得到的试验结果很好地反映了金属材料在磨损和腐蚀共同作用下的特征行为。在牙科树脂材料方面，我们使用一整块假牙作为测试样本，因为它是由三种不同类型的树脂组成的复合材料。3 .重复碰撞试验表明，齿高的降低不是由磨损引起的，而是由整个齿片的变形引起的；其次，在50000次左右的碰撞频率下，变形行为发生了变化；第三，低载荷重复碰撞试验显示出不同于高载荷单次加载试验的材料特征行为。在试验结果的基础上，提出了一种新的口腔环境下口腔材料的试验方法。少

The purpose of this investigation is to develop testing methods to evaluate dental materials that are exposed in mouth to the combined attack of microbe corrosion and mechanical forces that are caused through the collision of teeth.1. The determination of dynamic wear condition : Stresses which are originated on teeth while chewing soft or hard foods were determined by use of a load sensor (Tekscan) to obtain the extent of the maximum load, loading speed and the contact duration, which were ranged from 4-13 kgf, 0.03-0.07 kgf/ms, 420-500 ms respectively.2. The degradation process of dental materials and the index of degradation : The delinquent in teeth meeting due the decrease in teeth height was taken up so that the decrease in the teeth height was chosen as the index of degradation.3. Development of testing method : As to metallic materials, the teeth meeting were simulated through the combination of a flat plate (specimen) and a sphere (Al_2O_3). Repeated load was applied through t … More he sphere to the specimen to produce an indentation on the surface of which diameter is proportional to the depth of indentation, that is, the decrease in teeth height.It increased with the test duration as an exponential function of loading frequency, which revealed some relation with the delayed movement of dislocation. Those test results obtained in a 3 % NaCl solution were proved to represent well the characteristic behavior of metallic materials that are exposed to the combined attack of wear and corrosion.As to dental resin materials, a whole piece of false tooth was used as test specimen because it is a composite that consists of three different types of resin. Repeated collision test revealed firstly that the decrease in teeth height is caused not through wear but through the deformation of whole tooth piece, secondly that the deformation behavior changes its manner at the collision frequency of about 50000 times, and thirdly that the repeated collision test with low load reveals a characteristic behavior of material different from that of a single time loading test with a much higher load.4. Basing on the test results, a new test method for the dental materials in mouth environment were proposed. Less