Dynamic viscoelastic behavior of resin cements measured by torsional resonance

Objective. The purpose of the study was to measure the viscoelastic properties of four dental resin composite cements using a dynamic mechanical analysis technique. Methods. Dynamic torsional loading was conducted in the frequency range from 1 to 80 Hz. Cement specimens were tested after storage in 37 °C water for 24 h. One group was thermal cycled prior to testing. Measurements were taken at 21, 37, and 50 °C. Storage modulus, loss tangent and other viscoelastic parameters were determined from the amplitude/frequency curves. Results. Storage moduli of the cements ranged from 2.9 to 4.1 GPa at 37 °C. Loss tangents ranged from 0.054 to 0.084. Storage moduli decreased in a regular way with increasing temperature, whereas, loss tangents increased. Thermal cycling caused small decreases in storage moduli. Significance. Resin cements with higher filler loading were found to have higher storage moduli and lower loss tangents. Since these properties have been associated with better clinical performance in the areas of retention and prevention of fracture of porcelain and resin restorations, the more highly filled cements may be recommended. Temperature variations influenced viscoelastic behavior of the cements. However, within the temperature range studied no sharp drop in modulus was seen, so the materials should function satisfactorily in the oral cavity.