title: Influence of time on bond strength after bleaching with 35% hydrogen peroxide.
abstract: OBJECTIVE
  The aim of this in vitro study was to evaluate the influence of time after treatment with a 35% hydrogen peroxide bleaching agent on the shear bond strength between composite resin and sound enamel and dentin.
  
  
  METHODS
  Eighty dental slabs - 40 enamel (E) slabs and 40 dentin (D) slabs - were embedded, flatted, and divided into four groups (n=10). In G1 the E and D slabs were kept in artificial saliva for 14 days. For the G2, G3, and G4 groups the E and D slabs were submitted to bleaching treatment with a 35% hydrogen peroxide bleaching agent. At different times after bleaching treatments (G2=immediate; G3=seven days; G4= fourteen days), composite resin cylinders were made using an adhesive system. Tests were performed in a universal testing machine at a speed of 0.5 mm/min to obtain the values in MPa.
  
  
  RESULTS
  For enamel, the Kruskal-Wallis test and Dunn Method showed G1 differed significantly from G2 (G1=13.40 a; G2=6.64 b; G3=16.76 a; G4=11.64 ab). For dentin, the analysis of variance (ANOVA) and Tukey tests showed that G1 differed significantly from G2 and G3 (G1=12.11 a; G2=4.97 b; G3=8.67 c; G4=11.86 ac).
  
  
  CONCLUSIONS
  It is recommended adhesive restorative procedures in enamel be delayed for seven days post-bleaching treatment with 35% hydrogen peroxide, while restorations in dentin should be delayed for 14 days following bleaching treatment.
authors.affiliation: School of Dentistry and Dental Research Center, São Leopoldo Mandic, Campinas, SP, Brazil. dra_cinthia@hotmail.com
authors.forename: Cinthia Maria
authors.initials: CM
authors.lastname: Barbosa
authors.forename: Robson Tetsuo
authors.initials: RT
authors.lastname: Sasaki
authors.forename: Flavia Martao
authors.initials: FM
authors.lastname: Florio
authors.forename: Roberta Tarkany
authors.initials: RT
authors.lastname: Basting
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D001840:Dental Bonding; D003743:Dental Enamel / Q000187:drug effects*; D003799:Dental Stress Analysis; D003804:Dentin / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects*; D016877:Oxidants / Q000009:adverse effects*; D019279:Resin Cements; D033081:Shear Strength; D018709:Statistics, Nonparametric; D013997:Time Factors; D014073:Tooth Bleaching / Q000009:adverse effects*
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D016877:Oxidants; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D006861:Hydrogen Peroxide