title: Evaluation of a 6% hydrogen peroxide tooth-whitening gel on enamel microhardness after extended use.
abstract: OBJECTIVE
  To evaluate the effects of a 6% hydrogen peroxide tooth whitener, Xtra White, on sound human enamel microhardness in vitro after an extended and exaggerated simulated 8 weeks of product use.
  
  
  METHODS
  Polished human enamel specimens were prepared and baseline microhardness and color measurements determined. The enamel specimens were exposed to a fluoride-containing toothpaste for 30 seconds and then exposed to water, Xtra White, a control carbopol gel containing no hydrogen peroxide, or a carbonated beverage (each group, n = 8) for 20 minutes. Specimens were exposed to whole saliva at all other times. In order to simulate 8 weeks of extended product use, quadruple the length of the manufacturer's instructions, 112 treatments, were conducted. Microhardness measurements were taken after 2, 4, 6, and 8 weeks of simulated treatments, and color was measured after 2 and 8 weeks.
  
  
  RESULTS
  The Xtra White-treated specimens showed a statistically significant (P < .0001) increase in L* and decrease in b* compared to the water-treated specimens after 2 weeks simulated use, indicating bleaching had occurred. The carbonated beverage-treated specimens were significantly softened (P = .0009) compared to baseline after only 1 treatment. The carbopol gel-treated specimens were significantly softened (P = .0028) after 2 weeks of simulated treatments compared to baseline. There were no statistically significant differences in enamel microhardness between baseline and all treatment times for XW and water groups.
  
  
  CONCLUSIONS
  Xtra White does not have any deleterious effects on sound human enamel microhardness after an extended and exaggerated simulated 8 weeks of product use.
authors.affiliation: Unilever Oral Care, Bebington, Wirral, UK.
authors.forename: Mariarosaria
authors.initials: M
authors.lastname: Toteda
authors.forename: Carole J
authors.initials: CJ
authors.lastname: Philpotts
authors.forename: Trevor F
authors.initials: TF
authors.lastname: Cox
authors.forename: Andrew
authors.initials: A
authors.lastname: Joiner
mesh_terms: D000180:Acrylic Resins; D002253:Carbonated Beverages / Q000633:toxicity; D003116:Color; D003743:Dental Enamel / Q000187:drug effects*; D006244:Hardness / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D016877:Oxidants / Q000633:toxicity*; D011145:Polyvinyls / Q000633:toxicity; D013997:Time Factors; D014073:Tooth Bleaching / Q000009:adverse effects*
chemical_list: D000180:Acrylic Resins; D016877:Oxidants; D011145:Polyvinyls; C006912:carboxypolymethylene; D006861:Hydrogen Peroxide