title: In-office bleaching gel with 35% hydrogen peroxide enhanced biofilm formation of early colonizing streptococci on human enamel.
abstract: OBJECTIVE
  To compare the effects of 25% and 35% hydrogen peroxide in-office bleaching systems on surface roughness and streptococcal biofilm formation on human enamel.
  
  
  METHODS
  Enamel specimens (3mm×3mm×2mm, n=162) from human permanent teeth were randomly divided into 3 treatment groups (n=54 each): (1) control, (2) bleached with 25% hydrogen peroxide (Zoom2™), and (3) bleached with 35% hydrogen peroxide (Beyond™). The enamel surface roughness was measured by a profilometer before and after treatments. Subsequently, the treated enamel specimens were randomly placed into 3 subgroups (n=18 each) and incubated with: (1) trypticase soy broth control, (2) Streptococcus mutans culture and (3) Streptococcus sanguinis culture for 24h. Biofilm formation was quantified by crystal violet staining. The biofilm structure on three specimens from each group was visualized by scanning electron microscopy. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests with Bonferroni corrections. Significance level was set at p<0.05.
  
  
  RESULTS
  Both bleaching systems significantly reduced enamel surface roughness comparing to the control group (p<0.001), but there was no difference between the two treatment groups. Remarkably, S. sanguinis biofilm formation was significantly higher on enamel specimens bleached with 35% hydrogen peroxide than other treatments (p<0.001), but was lower on those bleached with 25% hydrogen peroxide (p<0.001). In contrast, no difference in S. mutans biofilm formation was observed among the three treatment groups.
  
  
  CONCLUSIONS
  Both 25% and 35% hydrogen peroxide caused similar degrees of reduction in enamel surface roughness. Nevertheless, bleaching with 35% hydrogen peroxide appeared to markedly promote S. sanguinis biofilm formation.
  
  
  CONCLUSIONS
  The increase of early colonizer biofilm raised concerns over adverse effects of in-office bleaching on plaque formation. This should be further investigated in vivo and efficient plaque control should be emphasized after bleaching with high concentrations of hydrogen peroxide.
authors.affiliation: Esthetic Restorative and Implant Dentistry Program, Chulalongkorn University, Henri-Dunant Road, Bangkok 10330, Thailand.
authors.forename: Suttinee
authors.initials: S
authors.lastname: Ittatirut
authors.affiliation: Department of Microbiology and DRU on Oral Microbiology, Faculty of Dentistry, Chulalongkorn University, Henri-Dunant Road, Bangkok 10330, Thailand. Electronic address: oranart@gmail.com.
authors.forename: Oranart
authors.initials: O
authors.lastname: Matangkasombut
authors.affiliation: Department of Microbiology and DRU on Oral Microbiology, Faculty of Dentistry, Chulalongkorn University, Henri-Dunant Road, Bangkok 10330, Thailand. Electronic address: tpanida@gmail.com.
authors.forename: Panida
authors.initials: P
authors.lastname: Thanyasrisung
mesh_terms: D001431:Bacteriological Techniques; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D003743:Dental Enamel / Q000382:microbiology* / Q000648:ultrastructure; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000494:pharmacology*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010789:Phototherapy / Q000379:methods; D011897:Random Allocation; D013291:Streptococcus / Q000187:drug effects* / Q000254:growth & development; D013295:Streptococcus mutans / Q000187:drug effects / Q000254:growth & development; D013298:Streptococcus sanguis / Q000187:drug effects / Q000254:growth & development; D058205:Tooth Bleaching Agents / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide
keywords: Biofilm formation; Enamel; Hydrogen peroxide; In-office bleaching; Streptococcus mutans; Streptococcus sanguinis