A comparative study of the bond strengths of amalgam and alloy–glass ionomer cores

The purpose of this study was to compare the bond strengths of dental amalgam cores and dental alloy‐glass ionomer cores that were luted to cast gold crowns with glass ionomer cement. Seventy‐two human extracted molars were sectioned horizontally and four regular thread mate system pins were inserted into a flat pulpal floor. The teeth were restored with amalgam or alloy‐glass ionomer admixture and prepared for crown preparations. Castings were produced with type III gold and cemented to the cores with Fuji type I glass ionomer cement. Thirty‐six of the specimens were subjected to thermal fatigue by cycling between 4 and 50°C for periods of 1, 5 and 10 weeks. The remainder of the specimens were retained in deionized water at 37°C. Bond strengths of the cores, in tension, were measured with a universal testing machine. The alloy‐glass ionomer cores exhibited higher bond strengths than the amalgam cores for virtually all time periods, particularly the thermocycled samples. The alloy‐glass ionomer cores exclusively displayed core fractures and pin/tooth insufficiencies while the amalgam cores failed because of a deterioration of the glass ionomer luting cement.