Bond strength durability of direct and indirect composite systems following surface conditioning for repair.
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.
Passos
Sheila Pestana
SP
Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos Campos, Brazil.
Ozcan
Mutlu
M
Vanderlei
Aleska Dias
AD
Leite
Fabiola Pessoa Pereira
FP
Kimpara
Estevão Tomomitsu
ET
Bottino
Marco Antonio
MA
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
D003188:Composite Resins; D012821:Silanes; D012822:Silicon Dioxide; D006858:Hydrofluoric Acid