Apparent modulus of elasticity of dental amalgams.

The modulus of elasticity of dental amalgam has been determined by analysis of creep data (OGLESBY ET AL, J Res Natl Bur Stan 72C: 203, 1968) and by ultrasonic methods (DICKSON and OGLESBY, J Dent Res 46: 1475, 1967; HALL ET AL, J Dent Res 52: 390, 1973) to be between 63,000 and 70,000 MN/m2. These values represent the instantaneous elastic compliance term when dental amalgam is treated as a viscoelastic material. It is convenient, however, to approximate the behavior of dental amalgam as elastic in experimental stress analysis models. Thus, an apparent modulus of elasticitv (E') can be determined by measurement of the slope of a stress-strain curve in compression at a given loading rate. Values of E' determined in this manner for conventional dental amalgams at the one-week period were from 9,660 to 12,400 MN/M2 within a stress range from 34.5 to 172 MN/M2 at a loading rate of 0.008 cm/min (TAYLOR ET AL, J Dent Res 28: 228, 1949). Values of El and compressive strength (S) were determined for five dental amalgams at 24-hour and one-month periods. Cylindrical specimens were prepared, using the procedure described in American Dental Association Specification no. 1 (Guide to Dental Materials and Devices, 1975),