Influence of frequency on shear fatigue strength of resin composite to enamel bonds using self-etch adhesives

Objectives: The purpose of this study was to determine the influence of different frequency rates on of bond durability of self-etch adhesives to enamel using shear fatigue strength (SFS) testing. Methods: A two-step self-etch adhesive (OX, OptiBond XTR), and two single step self-etch adhesives (GB, G-[U+04D5]nial Bond and SU, Scotchbond Universal) were used in this study. The shear fatigue strength (SFS) to enamel was obtained. A staircase method was used to determine the SFS values with 50,000 cycles or until failure occurred. Fatigue testing was performed at frequencies of 5 Hz, 10 Hz, and 20 Hz. For each test condition, 30 specimens were prepared for the SFS testing. Results: Regardless of the bond strength test method, OX showed significantly higher SFS values than the two single-step self-etch adhesives. For each of the three individual self-etch adhesives, there was no significant difference in SFS depending on the frequency rate, although 20 Hz results tended to be higher. Conclusions: Regardless of the self-etch adhesive system, frequencies of 5 Hz, 10 Hz, and 20 Hz produced similar results in fatigue strength of resin composite bonded to enamel using 50,000 cycles or until bond failure. Significance: Accelerated fatigue testing provides valuable information regarding the long term durability of resin composite to enamel bonding using self-etch adhesive system.