Method: Commercially available dental cements, bases, and liners (polycarboxylate, zinc phosphate, composite, and glass-ionomer) were evaluated. Diametral tensile strength was determined on disks 3 mm thick and 6 mm in diameter. Compressive strength and modulus of elasticity in compression were determined on cylinders 4 mm in diameter and 8 mm in height. Measurements were made at two temperatures, room temperature (23o C) and mouth temperature (37° C). Samples were maintained at constant temperature during testing using a temperature cabinet on an Instron testing machine at a crosshead displacement rate of 0.05 mm/min.
Result: Two way analysis of variance and Tukey intervals (P<0.05) showed significant differences between several of the cements tested in each category. The increased temperature changed significantly (P<0.05) the mechanical properties of the materials tested. Diametral tensile strength decreased for all tested cements. The compressive strength and modulus of elasticity decreased for polycarboxylate, zinc phosphate and composite cements and increased for Ketac-Bond glass ionomer cement.
Conclusion: The effects of temperature change on the mechanical properties of cements, liners, and bases may be critical when placed beneath a restoration.