title: Effect of different photoactivation methods on the bond strength of composite resin restorations by push-out test.
abstract: OBJECTIVE
  Modulated curing methods could lead to a higher probability of bond preservation. Therefore, the aim of this study was to evaluate the effect of 7 curing methods on bond strength of composite resin restorations.
  
  
  METHODS
  Seventy bovine incisors were selected. A conical cavity was prepared in the buccal surface. Adper Single Bond adhesive system was applied according to the manufacturer's instructions, and the cavities were filled with a single increment of Esthet X (Dentsply/Caulk). The specimens were randomly assigned into 7 groups (n = 10) according to the photoactivation method: (1) continuous light 700 (700 mW/cm2) (control); (2) continuous light 150 (150 mW/cm2); (3) continuous light 250 (250 mW/cm2); (4) soft-start 75 (75 mW/cm2) + 700 mW/cm2); (5) soft-start 150 (150 mW/cm2 + 700 mW/cm2); (6) pulse-delay (150 mW/cm2 + 3 minutes + 700 mW/cm2); and (7) intermittent light (cycles at 600 mW/cm2). The energy density for all groups was 14 J/cm2. The bond strength of the composite restorations was measured by performing the push-out test in a universal testing machine (Instron). The results were submitted to ANOVA and Tukey test (P < .05).
  
  
  RESULTS
  Pulse-delay, soft-start 150, and soft-start 75 methods showed a significant increase in bond strength when compared with the control continuous light 700 method. Low power density and intermittent light groups showed intermediate results.
  
  
  CONCLUSIONS
  Modulation of the energy density during light curing of composite resins using pulse-delay or soft-start methods increased the bond strength of composite restorations.
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School-Unicamp, São Paulo, Brazil.
authors.forename: Leonardo Gonçalves
authors.initials: LG
authors.lastname: Cunha
authors.forename: Roberta Caroline Bruschi
authors.initials: RC
authors.lastname: Alonso
authors.forename: Gisele Maria
authors.initials: GM
authors.lastname: Correr
authors.forename: William Cunha
authors.initials: WC
authors.lastname: Brandt
authors.forename: Lourenço
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.forename: Mário Alexandre Coelho
authors.initials: MA
authors.lastname: Sinhoreti
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000528:radiation effects; D002417:Cattle; D003188:Composite Resins / Q000528:radiation effects*; D001840:Dental Bonding; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D008027:Light; D008422:Materials Testing; D044367:Phase Transition; D011897:Random Allocation; D019279:Resin Cements / Q000528:radiation effects*
chemical_list: D003188:Composite Resins; C466112:Esthet-X; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate