Nagarajan Venkata S, Jahanmir Said, Thompson Van P
National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Dent Mater. 2004 Jan;20(1):63-71. doi: 10.1016/s0109-5641(03)00069-1.
The aim of this study is to determine the in vitro two-body contact wear mechanisms of three medium filled composites and compare these with a highly filled composite previously investigated.
Three commercial dental composites with filler mass fraction loading of 75-76% were evaluated. Two of the composites contained Ba-B-Al-silicate glass fillers and fumed silica with different particle sizes and distributions. One of these composites contained a fairly uniform distribution of filler particles ranging in size from 1 to 5 microm, whereas the particle size distribution in the second composite was bimodal consisting of small (less than 1 microm) and large (about 10 microm) particles. The third composite contained Ba-Al-silicate glass and silica with a filler particle size of approximately 1 microm. The composite disks were tested for wear against harder alumina counterfaces. Wear tests were conducted in distilled water using a pin-on-disk tribometer under conditions that represented typical oral conditions (sliding speed of 2.5 mm/s and contact loads ranging from 1 to 20 N). The wear tracks were analyzed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy to elucidate the wear mechanisms. The chemical composition of the water solution collected after the tests was determined using an inductively coupled plasma-mass spectrometer (ICP-MS) to detect possible chemical changes, e.g. dissolution of trace elements due to submersion or wear. The wear results were compared with those reported in an earlier study on a highly filled composite containing predominately alumino-silicate glass fillers and alumina at a filler loading of 92%.
The differences in two-body wear rates between the three medium filled composites were not statistically significant (p<0.05) indicating that the variations in filler particle size and slight differences in chemical composition of the glass fillers do not affect the in vitro wear rates of these composites. Wear rates of these medium filled composites, however, were significantly lower than the highly filled composite (p<0.05). SEM, FTIR and ICP-MS analyses suggested that wear in the medium filled composites occurs by a complex set of processes involving tribochemical reactions between filler particles and water, formation of surface films containing a mixture of filler fragments and reaction products, and film delamination, as well as dissolution of the reaction products.
This study reveals that subtle changes in the filler particle size and small differences in filler composition do not significantly affect the two-body wear behavior of medium filled composites. However, the chemistry of filler particles plays an important role in altering the wear performance of composites when significant changes are made in the chemical composition of the fillers and when the filler loading is increased.
本研究旨在确定三种中等填料含量复合材料的体外双体接触磨损机制，并将其与先前研究的高填料含量复合材料进行比较。
评估了三种填料质量分数为75 - 76%的商用牙科复合材料。其中两种复合材料含有不同粒径和分布的钡硼铝硅酸盐玻璃填料和气相二氧化硅。其中一种复合材料的填料颗粒尺寸范围为1至5微米，分布较为均匀，而另一种复合材料的颗粒尺寸分布为双峰型，由小颗粒（小于1微米）和大颗粒（约10微米）组成。第三种复合材料含有钡铝硅酸盐玻璃和二氧化硅，填料颗粒尺寸约为1微米。对复合材料圆盘与硬度更高的氧化铝对偶面进行磨损测试。在蒸馏水中使用销盘摩擦磨损试验机进行磨损测试，测试条件模拟典型口腔环境（滑动速度为2.5毫米/秒，接触载荷范围为1至20牛）。通过扫描电子显微镜（SEM）和傅里叶变换红外（FTIR）光谱分析磨损轨迹，以阐明磨损机制。使用电感耦合等离子体质谱仪（ICP-MS）测定测试后收集的水溶液的化学成分，以检测可能的化学变化，例如由于浸泡或磨损导致的微量元素溶解。将磨损结果与早期一项关于高填料含量复合材料的研究结果进行比较，该高填料含量复合材料主要含有铝硅酸盐玻璃填料和氧化铝，填料含量为92%。
三种中等填料含量复合材料之间的双体磨损率差异无统计学意义（p<0.05），表明填料颗粒尺寸的变化和玻璃填料化学成分的细微差异不会影响这些复合材料的体外磨损率。然而，这些中等填料含量复合材料的磨损率显著低于高填料含量复合材料（p<0.05）。SEM、FTIR和ICP-MS分析表明，中等填料含量复合材料的磨损是由一系列复杂过程引起的，包括填料颗粒与水之间的摩擦化学反应、形成含有填料碎片和反应产物混合物的表面膜以及膜分层，以及反应产物的溶解。
本研究表明，填料颗粒尺寸的细微变化和填料成分的微小差异不会显著影响中等填料含量复合材料的双体磨损行为。然而，当填料的化学成分发生显著变化以及填料含量增加时，填料颗粒的化学性质在改变复合材料的磨损性能方面起着重要作用。
