The use of ultrasonication to study remineralisation of eroded enamel

The aim of this study was to use ultrasonication and profilometry as method s to study de- and remineralisation of citric acid-eroded enamel at differe nt pH values. Seventy-eight polished human enamel samples were divided into three test and three control groups of 13 specimens each. Three specimens of each group were chosen for SEM examination. The samples were exposed to 0.3% citric acid at pH 2.54, 3.2 or 4.5 for 2 h. The depths of the resultin g lesions were measured by profilometry, The test groups were placed in art ificial saliva and the control groups were stored in saline (0.9% NaCl) for 24 h and new profiles recorded. Finally all specimens were ultrasonicated in water for 5, 30, 120, 240 and 480 s with profilometric measurements at e ach time point. Ultrasonication of the test groups after remineralisation s howed little effect on the lesion depth, whereas the control groups had an enamel loss of 2.1 mum at pH 2.54, 2.9 mum at pH 3.2 and 0.4 mum at pH 4.5 after 30-second ultrasonication. These differences from respective test gro ups were statistically significant at pH 2.54 and 3.2 but not at pH 4.5. Ul trasonication of control pH 2.54 and 3.2 specimens removed an amorphous cov ering layer to reveal a flattened surface with prisms outlined by prism bou ndaries. It can be concluded that remineralisation in artificial saliva sta bilises the surface softened enamel against ultrasonication. Copyright (C) 2001 S. Karger AG, Basel.