Evaluation of a 6% hydrogen peroxide tooth whitening gel on enamel and dentine microhardness in vitro

Summary Objectives. The aims of this study were to evaluate the effects of a novel 6% hydrogen peroxide containing tooth whitener, Xtra White (XW), on enamel and dentine microhardness in vitro. Methods. Polished human enamel and dentine specimens were prepared and baseline microhardness determined. In study 1, enamel specimens were exposed to 20 min cycles of either water, XW or Sprite Light for up to 28 cycles. In studies 2 and 3, enamel specimens were treated with 20 min cycles of either XW or water and exposed to whole saliva at all other times. In study 3, an additional exposure to a fluoride containing toothpaste was conducted. In total, 28 treatments were conducted in order to simulate a 2 weeks product use. In study 4, dentine specimens were treated as per study 3. Final microhardness measurements were taken and for studies 3 and 4 colour measurements were additionally taken. Results. XW and water gave no statistically significant ðp . 0:05Þ changes in enamel and dentine microhardness after 28 treatments. Sprite Light gave a significant ðp , 0:00002Þ reduction in enamel microhardness after one 20 min treatment. XW showed significant bleaching of enamel and dentine specimens as compared to the water control. Conclusions. XW does not have any significant effect on enamel and dentine microhardness.