title: Thirty-five percent carbamide peroxide application causes in vitro demineralization of enamel.
abstract: OBJECTIVE
  The objective of this in vitro study was to investigate whether a high concentration 'in-office' bleaching agent affected the mineral content of enamel and dentin.
  
  
  METHODS
  A commercially available 35% carbamide peroxide bleaching agent was applied for 2h to sectioned teeth (n=11). Specimens were then immersed in artificial saliva at 37 degrees C for a further 24h to simulate the oral environment. Tomographic images of these sections were obtained (micro-CT 80, Scanco, Switzerland) prior to and post-bleach application. Eight three-dimensional regions of interest (ROI), starting from the enamel surface extending to the dentinoenamel junction, were selected for each section. The hydroxyapatite equivalent mineral concentrations (g/cm(3)) of the ROIs were calculated. Any changes in mineral content as a consequence of the bleaching procedure were calculated in relation to each ROI.
  
  
  RESULTS
  There was a significant reduction in the mineral content of enamel specimens post-bleach application extending to a depth of 250microm (paired t-test, p<0.05); this reduction in mineral content was greatest in the ROI's closest to the tooth surface. There was, however, no significant difference in the mineral content of dentin as a consequence of bleaching.
  
  
  CONCLUSIONS
  This in vitro study has shown that significant demineralization of enamel occurred following bleaching with 35% carbamide peroxide. The concept that 'in-office' bleaching is a non-destructive cosmetic procedure should be reconsidered.
authors.affiliation: Department of Fixed & Removable Prosthodontics, Level 6 Worsley Building, Leeds Dental Institute, University of Leeds, Clarendon Way, Leeds LS2 9LU, UK. n.efeoglu@leeds.ac.uk
authors.forename: Neslihan
authors.initials: N
authors.lastname: Efeoglu
authors.forename: David J
authors.initials: DJ
authors.lastname: Wood
authors.forename: Candan
authors.initials: C
authors.lastname: Efeoglu
mesh_terms: D000077463:Carbamide Peroxide; D003743:Dental Enamel / Q000187:drug effects*; D003804:Dentin / Q000187:drug effects; D004338:Drug Combinations; D006801:Humans; D008963:Molar; D016877:Oxidants / Q000633:toxicity*; D010545:Peroxides / Q000633:toxicity*; D014073:Tooth Bleaching / Q000009:adverse effects*; D017001:Tooth Demineralization / Q000139:chemically induced*; D014508:Urea / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea