title: Effect of home-use and in-office bleaching agents containing hydrogen peroxide associated with amorphous calcium phosphate on enamel microhardness and surface roughness.
abstract: BACKGROUND
  The effects of amorphous calcium phosphate (ACP)-containing bleaching agents on enamel surface have not been clarified yet.
  
  
  OBJECTIVE
  The study aims to evaluate the effects of different bleaching agents, either associated with ACP, or not, on enamel Knoop microhardness (KHN) and surface roughness (SR).
  
  
  METHODS
  The home-use hydrogen peroxide (HP) bleaching agents PolaDay 7.5% (HP7.5; SDI Limited, Bayswater, Victoria, Australia), PolaDay 9.5% (HP9.5; SDI Limited); DayWhite ACP-7.5% (ACP7.5; Discus Dental, Culver City, CA, USA) and DayWhite ACP 9.5% (ACP9.5; Discus Dental), and the in-office agents PolaOffice 35% (HP35; SDI Limited) and Opalescence XtraBoost 38% (HP38; Ultradent Products, South Jordan, UT, USA) were applied to polished enamel slabs (N = 10) for 30 minutes/day for 21 consecutive days (home-use) or in one session a week, for 3 weeks (in-office). KHN and SR were tested before (baseline), during (7, 14, 21 days), and after (7 and 14 days in artificial saliva) the bleaching treatment.
  
  
  RESULTS
  KHN evaluation revealed no significant difference among bleaching agents (p > 0.05); however, there was a significant decrease during bleaching treatment (p < 0.0001). KHN values attained in the post-treatment phase were statistically similar to baseline values (p > 0.05). SR was not altered during and after treatment, with the exception of PH38, which showed an increase in SR during bleaching treatment and a recovery after treatment. The ACP7.5 showed a trend to decreasing SR values during the bleaching treatment, but this decrease was only significant when associated with 14 days of immersion in artificial saliva, when the enamel was less rough than at baseline.
  
  
  CONCLUSIONS
  Bleaching agents caused a decrease in enamel KHN, but values were recovered after treatment, showing the importance of saliva in recovering mineral content. SR was altered during or after treatment, depending on HP concentration/association with ACP. The beneficial effects of adding ACP to bleaching formulas on SR may be restricted to lower HP concentrations in association with the remineralizing effect of saliva.
  
  
  CONCLUSIONS
  No beneficial effects of adding ACP to bleaching formulas on enamel microhardness were observed, but these observations may be attributable to the lower hydrogen peroxide concentrations in association with the remineralizing effect of saliva, when considering the enamel roughness.
authors.affiliation: Operative Dentistry Department, School of Dentistry and Research Center São Leopoldo Mandic, Campinas, São Paulo, Brazil.
authors.forename: Daniel Rodrigues
authors.initials: DR
authors.lastname: DE Abreu
authors.forename: Robson Tetsuo
authors.initials: RT
authors.lastname: Sasaki
authors.forename: Flávia Lucisano Botelho
authors.initials: FL
authors.lastname: Amaral
authors.forename: Flávia Martão
authors.initials: FM
authors.lastname: Flório
authors.forename: Roberta Tarkany
authors.initials: RT
authors.lastname: Basting
mesh_terms: D002130:Calcium Phosphates / Q000008:administration & dosage / Q000494:pharmacology*; D003743:Dental Enamel / Q000187:drug effects* / Q000648:ultrastructure; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000494:pharmacology*; D008422:Materials Testing; D012464:Saliva, Artificial / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods; D058205:Tooth Bleaching Agents / Q000008:administration & dosage / Q000494:pharmacology*; D014089:Tooth Remineralization
chemical_list: D002130:Calcium Phosphates; D012464:Saliva, Artificial; D058205:Tooth Bleaching Agents; C519480:amorphous calcium phosphate; D006861:Hydrogen Peroxide