Comparative study of luting agents with composite resin cores.

This study compared bond strengths of zinc phosphate and polycarboxylate cements in cementing cast gold crowns to composite resin cores. The study also compared the effect of thermocycling on the bond strengths in tension of the two cements under varied storage and thermocycling conditions. Sixty standard cores were made from composite resin material. Gold alloy crowns were cast for each core and cemented with zinc phosphate or polycarboxylate cement. The samples were stored for 1 day or 1 month and then cycled with 60-second dwell times between 5 degrees C and 55 degrees C distilled water baths for 5, 100, or 1000 cycles. The controls were stored for the same periods and were not cycled. Overall comparison of both storage periods and all cycled and noncycled groups revealed that zinc phosphate cement had significantly higher bond strengths than polycarboxylate cement. Increasing the storage time before cycling significantly increased the bond strengths for both cements. There was no difference between any of the cycle periods or the noncycled controls for either cement.