Effects of thermocycling on amalgam and alloy-glass ionomer cores luted to cast gold crowns

The effectiveness of dental alloy-glass ionomer cores and dental amalgam cores for the retention of castings luted with polycarboxylate cement was investigated. Extracted human teeth were reduced horizontally, revealing a flat pulpa floor where 4 regular T.M.S. pins were placed and restored with amalgam or alloy-glass ionomer mixture. Crown tapers were standardized between 5° and 9° and the surface area was measured for each core. Castings were fabricated with Type III gold and cemented to the cores. Half of the samples were subjected to thermal stress for 1 week, 5 weeks or 10 weeks, while the other half were stored in room temperature deionized water. Bond strengths of the cores were measured in tension with a Universal testing machine. The effect of thermocycling increased the bond strength of the alloyglass ionomer cores and decreased the bond strength of the amalgam cores during each repective time period.