Effect of acidic agents on the wear behavior of a polymer infiltrated ceramic network (PICN) material

Polymer infiltrated ceramic network (PICN) materials exhibit desirable properties for replacement of tooth structure. However, their durability and their integrity in various oral environments, remain relatively unknown. The primary objective of this study is to investigate the effect of acidic agents on the wear behavior of PICNs. Twenty specimens were randomly assigned to four groups and then immersed in either deionized water (control) or acidic agents (2% acetic acid, citric acid or lactic acid solutions) at 37℃ for 4 weeks. Changes in the surface microhardness (SMH) and roughness were measured. Reciprocating wear tests were performed under artificial saliva to 10,000 cycles, and the coefficient of friction (COF) and wear depth were quantified to assess the wear behavior. Scanning electron microscopy (SEM) was used to analyze the wear morphology. Acid erosion decreased the SMH and increased surface roughness of the PICN, especially in lactic acid solution. For less than 2800 cycles, the acetic acid and citric acid groups showed higher COF and wear depths due to combined ceramic and polymer wear; the lactic acid group showed smaller COF and wear depth, due to a wear debris layer that acted as solid lubricant. Beyond 2800 cycles, all four groups exhibited similar COF values, as well as wear depth and wear morphology. Overall, acid erosion had a significant effect on the surface wear history of the PICN, but no effect on its long-term wear properties. Overall, the depth of acidic degradation of the PICN was rather limited.