Ultrasonication as a method to study enamel demineralisation during acid erosion

The aim of this study was to use ultrasonication as a method to measure sub surface demineralisation of enamel. Polished human enamel samples with surf ace profiles within +/-0.3 mu m were divided into 6 groups of 10 specimens. The groups of specimens were exposed to 0.3% citric acid (pH 3.2) for 30 m in, 1, 2, 3 or 4 h, The depths of the resulting lesions were measured using a profilometer, A control group was stored in water for 4 h. Ultrasonicati on in water was performed on the specimen groups for 5, 30, 120, 240 and 48 0 s with profilometric measurements at each time point. The depth of the er osion increased linearly with the exposure time, Most of the additional los s of enamel occurred with the 5-second ultrasonication, The 30-min and 1-ho ur erosion lesions were further deepened by approximately 1 mu m with 5 s o f ultrasonication, The 2-, 3- and 4-hour lesions were deepened by 2-4 mu m with 5 s of ultrasonication. There were no changes in the control group, It is concluded that ultrasonication removed softened enamel from the surface of the eroded enamel, Ultrasonication together with accurate measurement o f lesion depth by profilometry offers a useful method for studying the dept h of enamel softening associated with erosion. Copyright (C) 2000 S. Karger AG. Basel.