title: Effect of various aging protocols and intermediate agents on the bond strength of repaired composites.
abstract: OBJECTIVE
  To evaluate the effect of two adhesive systems and different aging protocols on the bond strength of a -repaired microhybrid composite.
  
  
  METHODS
  Eighty test specimens (n = 20) and 10 control specimens measuring 8 x 4 mm were fabricated of a microhybrid composite (4 Seasons, shade A2) and grouped according to time/aging protocol: G1: 24 h in artificial saliva; G2: 7 days in artificial saliva; G3: 30 days in artificial saliva; G4: artificial accelerated aging (AAA) for 384 h; G5: control. After aging, samples were submitted to three types of surface treatment: SB2: Adper Single Bond 2, a two-step adhesive (3M ESPE); SB3: Adper Scotchbond Multi-Purpose, a three-step adhesive (3M ESPE); C: without application of adhesive (control). After this, test specimens were repaired with the same composite of a different shade (C3), and submitted to the microtensile test at a crosshead speed of 0.5 mm/min. Failure modes were analyzed by scanning electron microscopy (Jeol JSM 7500). Statistical analysis was performed using ANOVA and Tukey's test (p < 0.05).
  
  
  RESULTS
  G2/SB2 presented significantly lower bond strength values in comparison with the other groups (p < 0.05). The control group presented the highest bond strength values, which differed statistically significantly from SB3, G3/SB2, and G4/SB2 (p < 0.05). Fractographic analysis demonstrated that most samples presented predominantly cohesive failures, excepting GI/SB2, which presented mixed and cohesive failures, and G4/SB2 and G1/SB3, which showed adhesive failures.
  
  
  CONCLUSIONS
  The repair was more effective when performed after a short period of time and when the 3-step adhesive system (SB3) was used.
authors.affiliation: University of Sao Paulo, Ribeirao Preto, Brazil.
authors.forename: Ana Beatriz
authors.initials: AB
authors.lastname: Sousa
authors.forename: Francisca Daniele
authors.initials: FD
authors.lastname: Silami
authors.forename: Lucas
authors.initials: L
authors.lastname: da Garcia
authors.forename: Lucas Zago
authors.initials: LZ
authors.lastname: Naves
authors.forename: Fernanda
authors.initials: F
authors.lastname: de Pires-de-Souza
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding / Q000379:methods*; D058250:Dental Restoration Repair; D003799:Dental Stress Analysis; D004356:Drug Storage; D012464:Saliva, Artificial; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D003188:Composite Resins; D012464:Saliva, Artificial