title: Effect of laser irradiation on crystalline structure of enamel surface during whitening treatment with hydrogen peroxide.
abstract: OBJECTIVE
  This study is to evaluate the effect of laser activation on the whitening and crystalline structure of enamel surface during whitening treatment with hydrogen peroxide.
  
  
  METHODS
  Bovine teeth were treated with whitening gel containing 35% hydrogen peroxide. A whitening gel was applied on the enamel surface for a period of 5 min, and then irradiated using a diode laser (740 nm) during whitening treatment for 0, 30, 60, 120 and 180s for the GL0-W, GL30-W, GL60-W, GL120-W and GL180-W groups, respectively. The total whitening application time was 30 min for all groups.
  
  
  RESULTS
  Laser-irradiated enamel groups showed a similar lightness compared to the GL0-W group. The thickness of porous layer observed on the enamel surface of GL0-W group was decreased by increasing the laser irradiation time. While the Ca and P contents of the GL0-W group were lower than those of the non-whitening treated group (GL0-C), the Ca and P contents of the GL180-W group were similar to those of the GL180-C group. The enamel crystallinity was dramatically decreased by whitening treatment without laser irradiation. However, the decrease of crystallinity was protected by laser irradiation during whitening treatment. Raman measurement verified that laser irradiation could prevent the loss of mineral compositions on enamel and maintain its crystalline structure.
  
  
  CONCLUSIONS
  The professional whitening treatment with hydrogen peroxide and diode laser activation improves not only the whitening effect but also protects the change of enamel structure compared to the treatment with only gel.
authors.affiliation: Department of Dental Materials and Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju 500-757, South Korea.
authors.forename: Jung-Hyun
authors.initials: JH
authors.lastname: Son
authors.forename: Ji-Hae
authors.initials: JH
authors.lastname: An
authors.forename: Byung-Kuk
authors.initials: BK
authors.lastname: Kim
authors.forename: In-Nam
authors.initials: IN
authors.lastname: Hwang
authors.forename: Yeong-Joon
authors.initials: YJ
authors.lastname: Park
authors.forename: Ho-Jun
authors.initials: HJ
authors.lastname: Song
mesh_terms: D000818:Animals; D002417:Cattle; D003460:Crystallization; D018360:Crystallography, X-Ray; D003743:Dental Enamel / Q000737:chemistry / Q000187:drug effects / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D013499:Surface Properties; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000494:pharmacology*; D017001:Tooth Demineralization / Q000517:prevention & control*
chemical_list: D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide