Correlation of microhardness and wear in differently eroded bovine dental enamel

The purpose of the study was to compare the microhardness data of differently eroded enamel surfaces with the wear caused by toothbrushing. Sixty bovine enamel specimens were polished and prepared for microhardness determination. The polished surfaces were covered with tape except for a 1.3 x 10.0 mm window. Fifteen specimens each were stored in an erosive beverage (Sprite Light) for either 1, 5 or 15 min. Each specimen was immersed in 10 ml of the beverage. The remaining 15 specimens were not eroded. Interferometrical analysis revealed that substance loss after 15 min of erosion was negligibly low (about 75 mm). In all specimens Vickers microhardness determinations were conducted on eroded (= final hardness) and non-eroded (= initial hardness) enamel surfaces. The specimens were subsequently submitted to toothbrushing abrasion using a slurry consisting of 1 g non-fluoridated dentifrice in 5 ml artificial saliva. The total amount of tooth wear due to erosion and subsequent abrasion was profilometrically evaluated. Statistical analysis revealed a significant decrease in hardness and a significant increase in wear with increasing time of storage in the erosive beverage. Overall regression analysis yielded a statistically significant correlation between both initial and final hardness and the amount of tooth wear. The correlation of abrasion and final hardness could be described by a quadratic mathematical function. It is concluded that the susceptibility of eroded enamel to toothbrushing abrasion can be correlated with Vickers microhardness values, thereby suggesting an overproportionate increase of abrasion with decreasing hardness values.