Previous studies mostly focused on the sliding wear behavior of human teeth, and little effort has been made so far to study the impact wear of human teeth. The objective of this study was to investigate the impact wear process and mechanism of human tooth enamel and the influence of water content within enamel. In this paper, the impact wear behaviors of fresh and dried human tooth enamel against SiC ceramic have been investigated using a specially designed impact test machine. Tests lasting up to 5 x 10(3), 5 x 10(4), 2.5 x 10(5), 5.5 x 10(5), 8 x 10(5) and 1 x 10(6) cycles were conducted, respectively. Results showed that for the fresh enamel, the surface damage was dominated by plastic deformation at the early stage of impact wear. Iridescent rings appeared around the impact mark as a result of the accumulation and spread of plastic deformation. As the impact wear progressed, delamination occurred on the surface of enamel, and thus the iridescent rings gradually disappeared. Wear loss increased rapidly with the increase of impact cycles. When a wear particle layer was formed on the enamel surface, the wear rate decreased. It was found that the surface hardness of enamel increased with the impact cycles, and no cracks appeared on the cross section of wear scar. Compared with the fresh enamel, the fracture toughness of dried enamel decreased, and thus there were microcracks appearing on the cross section of wear scar. More obvious delamination occurred on the worn surface of dried enamel, and no iridescent rings were observed. The wear loss of dried enamel was higher than that of fresh enamel. In summary, the impact wear behavior of sound human tooth enamel was metal-like to some degree, and no subsurface cracking occurred. The water content within enamel could increase its fracture toughness and protect the surface from impact wear. The wear mechanism of human tooth enamel is determined by its microstructure. (C) 2016 Elsevier Ltd. All rights reserved.
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机译：先前的研究主要集中在人牙齿的滑动磨损行为上，到目前为止，几乎没有做出任何努力来研究人牙齿的冲击磨损。这项研究的目的是研究人牙釉质的冲击磨损过程和机理以及牙釉质中水含量的影响。本文使用专门设计的冲击试验机研究了新鲜和干燥的人牙釉质对SiC陶瓷的冲击磨损行为。分别进行了长达5 x 10（3），5 x 10（4），2.5 x 10（5），5.5 x 10（5），8 x 10（5）和1 x 10（6）周期的测试。 。结果表明，对于新鲜的搪瓷，在冲击磨损的早期阶段，表面损伤主要由塑性变形引起。由于塑性变形的积累和扩散，在撞击痕迹周围出现了虹彩环。随着冲击磨损的进行，釉质表面发生分层，因此虹彩环逐渐消失。随着冲击周期的增加，磨损量迅速增加。当在搪瓷表面上形成磨损颗粒层时，磨损率降低。发现搪瓷的表面硬度随着冲击循环而增加，并且在磨损痕迹的横截面上没有出现裂纹。与新鲜牙釉质相比，干燥牙釉质的断裂韧性降低，因此在磨损疤痕的横截面上出现微裂纹。在干燥的搪瓷的磨损表面上发生了更明显的分层，并且没有观察到虹彩环。干燥的瓷釉的磨损损失高于新鲜的瓷釉。综上所述，健全的人牙釉质的冲击磨损行为在一定程度上呈金属样，且未发生亚表面裂纹。搪瓷中的水分可增加其断裂韧性并保护表面免受冲击磨损。人牙釉质的磨损机理取决于其微观结构。 （C）2016 Elsevier Ltd.保留所有权利。
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