Human and bovine enamel erosion under 'single-drink' conditions

Tooth-surface pH is lowered, during drinking, to a value close to the pH of the drink itself. After the drink is swallowed, the pH rises to baseline values but this process can take several minutes. Few techniques can quantify enamel erosion at timescales representative of single drinks. The objective of this study was to compare human and bovine erosion over acid-exposure times of 2 s to 1 h. Human and bovine enamel softening was compared in vitro using nanoindentation (2-60 s of exposure to acid) and tissue loss was compared using optical profilometry (1-60 min of exposure to acid). Nanoindentation revealed statistically significant softening after 2 s (human) and 5 s (bovine); there were no significant differences in hardness reduction for the two tissues at any time-point. Profilometry demonstrated statistically significant tissue loss after 20 min (human) and 10 min (bovine); bovine tissue loss progressed 30% faster than human tissue loss. These results support the use of bovine enamel as a substitute for human enamel in erosion studies, with the understanding that for moderate exposure times bovine enamel erodes 30% faster than human enamel. Nanoindentation can be used to detect enamel dissolution at timescales comparable to the oral dwell-time of a single 'mouthful' of a beverage.