Effect of remineralization on the nanomechanical properties and microtribological behaviour of acid-eroded human tooth enamel

Abstract Acid-eroded human tooth enamel is more susceptible to abrasion and attrition than intact enamel. Previous studies suggested that remineralization may be a useful way to improve the mechanical properties of acid-eroded enamel. The objective of our study was to investigate the effect of remineralization on the nanomechanical properties and microtribological behaviour of acid-eroded human tooth enamel. In this paper, enamel specimens were prepared from human molar teeth. The enamel specimens were first immersed in citric acid solution (pH = 3.20) for 10 min to obtain acid-eroded enamel specimens. Remineralization was conducted in vitro by immersing the acid-eroded enamel specimens in artificial saliva for 12 h. A nano-indentation/scratch tester was used to study the nanomechanical properties and microtribological behaviour of the enamel specimens. Results showed that a layer of mineral deposits was formed on the acid-eroded enamel surface after in vitro remineralization. Compared with the original enamel surface, this layer had a similar chemical composition, but a significantly different crystal orientation. The nanomechanical and microtribological properties of the acid-eroded enamel surface were significantly enhanced by remineralization. However, the loss of the hardness and Young's modulus of enamel surface by acid erosion could not be totally recovered after in vitro remineralization. The wear volume of the acid-eroded enamel decreased obviously after remineralization, but it was still much higher than that of the original enamel. In summary, remineralization in artificial saliva could improve the anti-wear properties of acid-eroded enamel. The results would be helpful to extend the understanding of the remineralization repair mechanism for acid-eroded human tooth enamel.