Erosion behavior of human tooth enamel in citric acid solution

In vitro erosion behavior of human tooth enamel in citric acid solution (pH=3.2) has been investigated. The surfaces of enamel after different erosion times were analyzed by means of various microscopic examinations. Results showed that no obvious substance loss occurred on the enamel surface at the early stage of erosion, and the erosive lesion was characterized mainly by partial demineralization and decreased microhardness. As the erosion time increased, a honeycomb-like structure appeared on the enamel surface as a result of severe dissolution of the enamel rods. Then substantial erosive substance loss happened. The loss increased almost linearly with the erosion time. Further friction-wear tests by a nano-scratch tester indicated that the erosion of enamel had significant influence on its friction and wear behaviors. Both the friction coefficient and wear loss of eroded enamel showed a strong dependence on erosion time. Understanding of dental erosion behavior would be useful for improving clinical management of tooth wear.