title: Bond strength durability of direct and indirect composite systems following surface conditioning for repair.
abstract: OBJECTIVE
  This study evaluated the effect of surface conditioning methods and thermocycling on the bond strength between a resin composite and an indirect composite system in order to test the repair bond strength.
  
  
  METHODS
  Eighteen blocks (5 x 5 x 4 mm) of indirect resin composite (Sinfony) were fabricated according to the manufacturer's instructions. The specimens were randomly assigned to one of the following two treatment conditions (9 blocks per treatment): (1) 10% hydrofluoric acid (HF) for 90s (Dentsply) + silanization, (2) silica coating with 30-im SiOx particles (CoJet) + silanization. After surface conditioning, the bonding agent was applied (Adper Single Bond) and light polymerized. The composite resin (W3D Master) was condensed and polymerized incrementally to form a block. Following storage in distilled water at 37 degrees C for 24 h, the indirect composite/resin blocks were sectioned in two axes (x and y) with a diamond disk under coolant irrigation to obtain nontrimmed specimens (sticks) with approximately 0.6 mm2 of bonding area. Twelve specimens were obtained per block (N=216, n=108 sticks). The specimens from each repaired block were again randomly divided into 2 groups and tested either after storage in water for 24 h or thermocycling (6000 cycles, 5 degrees C to 55 degrees C). The microtensile bond strength test was performed in a universal testing machine (crosshead speed: 1 mm/min). The mean bond strengths of the specimens of each block were statistically analyzed using two-way ANOVA (alpha = 0.05).
  
  
  RESULTS
  Both surface conditioning (p = 0.0001) and storage conditions (p = 0.0001) had a significant effect on the results. After 24 h water storage, silica coating and silanization (method 2) showed significantly higher bond strength results (46.4 +/- 13.8 MPa) than that of hydrofluoric acid etching and silanization (method 1) (35.8 +/- 9.7 MPa) (p < 0.001). After thermocycling, no significant difference was found between the mean bond strengths obtained with method 1 (34.1 +/- 8.9 MPa) and method 2 (31.9 +/- 7.9 MPa) (p > 0.05).
  
  
  CONCLUSIONS
  Although after 24 h of testing, silica coating and silanization performed significantly better in resin-resin repair bond strength, both HF acid gel and silica coating followed by silanization revealed comparable bond strength results after thermocycling for 6000 times.
authors.affiliation: Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos Campos, Brazil.
authors.forename: Sheila Pestana
authors.initials: SP
authors.lastname: Passos
authors.forename: Mutlu
authors.initials: M
authors.lastname: Ozcan
authors.forename: Aleska Dias
authors.initials: AD
authors.lastname: Vanderlei
authors.forename: Fabiola Pessoa Pereira
authors.initials: FP
authors.lastname: Leite
authors.forename: Estevão Tomomitsu
authors.initials: ET
authors.lastname: Kimpara
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Bottino
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins; D001840:Dental Bonding; D045662:Dental Etching / Q000379:methods*; D017269:Dental Prosthesis Repair; D003799:Dental Stress Analysis; D004356:Drug Storage; D006858:Hydrofluoric Acid; D011897:Random Allocation; D012821:Silanes; D012822:Silicon Dioxide; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D012821:Silanes; D012822:Silicon Dioxide; D006858:Hydrofluoric Acid