Mixing variables of zinc phosphate cement and their influence on the seating and retention of complete crowns.

Variations in the powder/liquid ratio, mixing time, and temperature of zinc phosphate cement were studied to determine their effect on the seating and retention of complete cast crowns. The crowns were made for extracted human molar teeth machined to an 8-degree convergence using a diamond instrument. Seating measurements were made between four pairs of marks using a machinist's microscope. A servohydraulic testing machine was used to measure retention values. A dynamic seating method allowed essentially complete seating of the castings in all groups. No statistically significant differences in retention between the groups were found.