title: Microtensile bond strength of enamel after bleaching.
abstract: OBJECTIVE
  To evaluate the bond strength of a composite resin to the bovine enamel bleached with 35% hydrogen peroxide. It was used an etching-and-rinse adhesive system employed immediately, 7 and 14 days after the bleaching.
  
  
  METHODS
  Twenty bovine teeth were randomly distributed into 4 groups (n = 5), 3 experimental and 1 control. G1: Unbleached + restoration 14 days after storage in artificial saliva (control); G2: Bleached + restoration immediately after bleaching; G3: Bleached + restoration 7 days after bleaching; G4: Bleached + restoration 14 days after bleaching. Their buccal enamel surfaces were flattened, and a 25 mm² (5 × 5 mm) area from each one of these regions was outlined so as to standardize the experimental region. Universal hybrid composite resin Filtek™Z350 was inserted into four layers of 1 mm each and photo-activated. The bond strength was quantitatively evaluated by a microtensile test (1.0 mm/min) 24 h after the restorative procedures. The failure mode was assessed through scanning electron microscopy (SEM).
  
  
  RESULTS
  There was a significant reduction in the bond strength of the restored teeth immediately after the bleaching (G2). There were no significant differences in enamel bond strength between groups G1, G3, and G4. There was a predominance of adhesive and mixed (cohesive + adhesive) failure in all groups.
  
  
  CONCLUSIONS
  The 7-day-period after the end of the bleaching with 35% hydrogen peroxide was enough to achieve the appropriate values of bond strength to the enamel.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry of São Paulo, University of São Paulo, São Paulo, SP, 05508-900, Brazil.
authors.forename: Andrea Dias Neves
authors.initials: AD
authors.lastname: Lago
authors.forename: Narciso
authors.initials: N
authors.lastname: Garone-Netto
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry; D003743:Dental Enamel / Q000648:ultrastructure*; D003764:Dental Materials / Q000737:chemistry; D003793:Dental Restoration, Permanent / Q000379:methods; D003799:Dental Stress Analysis / Q000295:instrumentation; D006861:Hydrogen Peroxide / Q000737:chemistry; D055115:Light-Curing of Dental Adhesives / Q000379:methods; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000737:chemistry; D011897:Random Allocation; D012464:Saliva, Artificial / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000737:chemistry
chemical_list: C554641:Adper single bond 2; D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; D010756:Phosphoric Acids; D012464:Saliva, Artificial; D058205:Tooth Bleaching Agents; C533204:filtek Z350; D006861:Hydrogen Peroxide; C030242:phosphoric acid