title: The bleaching depth of a 35% hydrogen peroxide based in-office product: a study in vitro.
abstract: OBJECTIVE
  The aim of the present study was to quantify the penetration of 35% hydrogen peroxide into enamel and dentine and to relate this to the resultant shade change of the tooth.
  
  
  METHODS
  The crowns of 24 caries and developmental defect free human maxillary incisors were stained internally with a standardised tea solution. Twelve specimens were power bleached with light activated 35% hydrogen peroxide and 12 placed in water; both exposure times were 30min. Three different shade assessment methods (Vita shade guide [SG], shade vision system [SVS] and a chromometer) were employed prior to, after tea staining and after power bleaching/water treatments. Twelve specimens each from the bleach group and the water control water group were sectioned mesio-distally. An additional 12 specimens from the bleach and the control group were sectioned labio-palatally. The stain area for each specimen was measured using image analysis software.
  
  
  RESULTS
  With tea staining, the mean changes in Vita shade guide units (SGU) ranged from 3.66 to 8.33. With the SVS system changes of 3.66-9 units were seen. Chromometer readings showed that following bleaching the L* values moved in the direction of black (3.8-6.7) and a* and b* values were in the red (0.3) and yellow (1.5) direction, respectively. Samples bleached and sectioned mesio-distally showed stain coverage of 28.6-39.4%, while palatal sections showed stain coverage of 58-72%. Control samples, whether sectioned mesio-distally or labio-palatally, showed staining throughout the dentine (97-100% coverage).
  
  
  CONCLUSIONS
  A 35% hydrogen peroxide in-office bleaching gel demonstrated bleaching into dentine of uniform depth.
authors.affiliation: Division of Restorative Dentistry, Department Oral and Dental Science, University of Bristol Dental School, Lower Maudlin St., Bristol BS1 2LY, UK.
authors.forename: M
authors.initials: M
authors.lastname: Sulieman
authors.forename: M
authors.initials: M
authors.lastname: Addy
authors.forename: E
authors.initials: E
authors.lastname: Macdonald
authors.forename: J S
authors.initials: JS
authors.lastname: Rees
mesh_terms: D000704:Analysis of Variance; D003743:Dental Enamel / Q000378:metabolism; D003745:Dental Enamel Permeability; D003804:Dentin / Q000378:metabolism*; D003806:Dentin Permeability; D006801:Humans; D006861:Hydrogen Peroxide / Q000493:pharmacokinetics* / Q000627:therapeutic use; D007180:Incisor; D016877:Oxidants / Q000493:pharmacokinetics* / Q000627:therapeutic use; D011897:Random Allocation; D013662:Tea / Q000009:adverse effects; D014073:Tooth Bleaching; D014075:Tooth Discoloration / Q000139:chemically induced / Q000628:therapy*
chemical_list: D016877:Oxidants; D013662:Tea; D006861:Hydrogen Peroxide