Crown retention: a comparative study of core type and luting agent

The in vitro bond strengths of both zinc phosphate and polycarboxylate cemented crowns to 4-pin amalgam and composite cores were investigated. The surface area and taper of each core were measured. The crowns were cemented to the cores and either stored for one week, 3 weeks, 6 weeks and 12 weeks or thermocycled for the same periods of time. The bond strength necessary to pull the crowns off the cores was measured using a universal testing machine. The bond strength was then represented as force/surface area. At all time periods, the composite resin with zinc phosphate cement showed significantly higher bond strengths than the other combinations of core type and cement.