Experimental studies of human dentine wear

Previous in vitro studies have described the relation between rates of enamel wear and variables such as applied load and lubricant pH. The aim here was to extend understanding of tooth-wear processes by considering the rate of wear in human dentine. Enamel was removed from extracted third molar teeth that had been sectioned mesiodistally. Moisture fluctuation within dentine was minimized by conducting all procedures under copious irrigation or in sealed containers of lubricant at pH 7.0. Specimens were subjected to wear using a purpose-built apparatus at loads of 6.2, 9.95 and 13.2 kg. All experiments were done with a unidirectional wear stroke of 3 mm at a rate of 80 cycles/min for 75 min and repeated for 75 min. Dentine wear was assessed by specimen weight loss. At pH 7.0, wear rates ranged from 0.50 mg/103 cycles at a load of 6.2 kg to 0.77 mg/103 cycles when a load of 13.2 kg was applied. At higher loads, dentine wear rates were similar to those of enamel. Increasing load is thus associated with a progressive increase in the rate of dentine wear. This relation differs significantly from that for enamel, reflecting fundamental differences in the composition and structure of these tissues.