LONG-TERM DURABILITY OF ADHESIVE SYSTEMS BONDED TO FRESH AMALGAM

A strong durable resin bond to fresh amalgam is desired in composite-v eneered amalgam restorations and in adhesive amalgam restorations. The purpose of this study was to evaluate the influence of long-term wate r storage on the durability of the shear bond strength of new adhesive systems bonded to fresh amalgam. Sixty cylindrical specimens composed of equal parts of amalgam and composite, with a layer of bonding mate rial in between, were prepared for each adhesive system: All-Bond 2, A malgambond Plus, High-Q-Bond, and Comspan. Specimens were divided into three subgroups and immersed in saline at 37 degrees C for either 48 hours, 3 months, or 6 months. After the immersion period, specimens we re thermocycled and subjected to shear bond strength testing. Shear bo nd strength of Comspan and High-Q-Bond adhesives did not deteriorate s ignificantly during the B-month experiment and maintained a mostly mix ed mode of failure. All-Bond 2 and Amalgambond Plus adhesives exhibite d deterioration of the shear bond strength as a function of immersion time and shifted from dominantly mixed mode of failure to totally adhe sive (All-Bond 2) or mostly adhesive failure (Amalgambond Plus). Incub ation in saline for long periods should be a standard test in evaluati ng the bond of new adhesive systems to fresh amalgam, whereas short ex posure time to water might be misleading.