title: Effects of Crest Whitestrips bleaching on surface morphology and fracture susceptibility of teeth in vitro.
abstract: OBJECTIVE
  This study examined the effects of peroxide tooth bleaching, including Crest Whitestrips hydrogen peroxide treatments, on the fracture susceptibility and surface morphology of human tooth enamel in vitro.
  
  
  METHODS
  Extracted human molars were ground and polished to prepare a uniform substrate for bleaching treatments. A cycling treatment methodology was employed which alternated ex vivo human salivary exposures with bleaching treatments under conditions of controlled temperature and durations of treatment. Bleaching treatments included commercial Crest Whitestrips bleaching gels, which utilize hydrogen peroxide as the in situ bleaching source, and several commercial carbamide peroxide bleaching gels. Control treatments included placebo gels and an untreated group. Crest Whitestrips bleaching included treatment exposures simulating recommended clinical exposures (14 hours of bleaching), along with excess bleaching simulating exposure to five times the suggested Crest Whitestrips use. At the conclusion of treatments, surface color measurements were taken to ensure tooth bleaching. Surface microhardness measures and surface morphological assessments with SEM were conducted to assess the effects of bleaching exposure on the surface morphology and mineral integrity of the teeth. These latter measures were then complemented with assessments of fracture susceptibility utilizing detailed analyses of crack propagation resulting from post-treatment microhardness indentations.
  
  
  RESULTS
  Surface microhardness and SEM measures revealed no deleterious effects on the enamel surfaces from any of the bleaching products assessed. This included conditions of excess bleaching exposure or "overbleaching." The analysis of fracture susceptibility similarly revealed no significant effects from tooth bleaching, regardless of the peroxide source.
  
  
  CONCLUSIONS
  These results confirm that tooth bleaching from the selected commercial hydrogen peroxide or carbamide peroxide bleaching systems do not produce changes in surface morphology, microhardness or fracture susceptibility of human tooth enamel under in vitro cycling conditions of treatment matching clinical bleaching exposures. These results support the clinical safety of the selected commercial bleaching systems to vital dentition, matching results obtained from the long-term use of these ingredients applied in dental offices and available in commercial formulations.
authors.affiliation: Procter and Gamble Company, Health Care Research Center, Mason, Ohio, USA. White.dj.1@pg.com
authors.forename: Donald J
authors.initials: DJ
authors.lastname: White
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Kozak
authors.forename: James R
authors.initials: JR
authors.lastname: Zoladz
authors.forename: Heinz J
authors.initials: HJ
authors.lastname: Duschner
authors.forename: Hermann
authors.initials: H
authors.lastname: Götz
mesh_terms: D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D003116:Color; D003124:Colorimetry; D003743:Dental Enamel / Q000187:drug effects* / Q000473:pathology; D004198:Disease Susceptibility; D004338:Drug Combinations; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000627:therapeutic use*; D008855:Microscopy, Electron, Scanning; D016877:Oxidants / Q000008:administration & dosage / Q000627:therapeutic use*; D010545:Peroxides / Q000627:therapeutic use; D010919:Placebos; D012463:Saliva / Q000502:physiology; D013997:Time Factors; D014073:Tooth Bleaching / Q000295:instrumentation / Q000379:methods*; D014082:Tooth Fractures / Q000503:physiopathology*; D014508:Urea / Q000031:analogs & derivatives* / Q000627:therapeutic use
chemical_list: D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D010919:Placebos; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide