title: Evaluation of a 6% hydrogen peroxide tooth whitening gel on enamel and dentine microhardness in vitro.
abstract: OBJECTIVE
  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 (p>0.05) changes in enamel and dentine microhardness after 28 treatments. Sprite Light gave a significant (p<0.00002) 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.
authors.affiliation: Unilever Oral Care, Quarry Road East, Bebington, Wirral, UK. andrew.joiner@unilever.com
authors.forename: Andrew
authors.initials: A
authors.lastname: Joiner
authors.forename: Gopal
authors.initials: G
authors.lastname: Thakker
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Cooper
mesh_terms: D002327:Cariostatic Agents / Q000494:pharmacology; D003116:Color; D003743:Dental Enamel / Q000187:drug effects*; D003804:Dentin / Q000187:drug effects*; D005459:Fluorides / Q000494:pharmacology; D005782:Gels; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000494:pharmacology*; D016877:Oxidants / Q000008:administration & dosage / Q000494:pharmacology*; D012463:Saliva; D014073:Tooth Bleaching; D014100:Toothpastes / Q000494:pharmacology; D014867:Water
chemical_list: D002327:Cariostatic Agents; D005782:Gels; D016877:Oxidants; D014100:Toothpastes; D014867:Water; D006861:Hydrogen Peroxide; D005459:Fluorides