Effect of fatigue upon the interfacial bond strength of repaired composite resins.

A comparative study of the fatigue limits of repaired samples of three composite resins was undertaken using the staircase technique. Following storage in water for 21 days at 23 degrees C the surfaces of the specimens to be bonded were ground with a fine Soflex disc, washed and dried. The surface was treated with either Scotchbond or a silane coupling agent, or left untreated, and a composite repair of the same material added. The specimens were thermally cycled and tested sequentially for 5000 cycles at different stress instruments using a transverse impact load. A statistically valid value for mean fatigue limit was determined for each design. This showed that resistance to fatigue forces was lower in repaired specimens than in complete specimens. The use of Scotchbond Dual Cure bonding agent gave the strongest repair.