Factors influencing the sealing behavior of retrograde amalgam fillings

In this study, the sealing behavior of apical (retrograde) amalgam fillings was evaluated with particular regard to the nature of the amalgam and the manipulative procedures used. With the use of an in vitro air pressure test, four high-copper alloys and one traditional composition low-copper alloy were selected for determination of their microleakage characteristics. Measurements were made on both normal and water-contaminated mixes, and the effect of mix plasticity was evaluated. In addition, both setting and postsetting dimensional changes of these alloys were determined. The results showed that amalgams differ in their ability to provide a complete seal and that low plasticity mixes result in greater microleakage. All zinc-containing alloys that were contaminated with water exhibited a postsetting or delayed expansion. However, only the low-copper alloy exhibited a delayed expansion of a magnitude that might induce root fracture.