Objective. The purpose of this investigation was to study the time-dependent creep and recovery behavior of some packable composites resins compared to a typical dispersion-phase amalgam alloy.

Methods. Three packable posterior composite resins (ALERT, SureFil, Solitaire®) were used as experimental groups and a high copper admixed amalgam alloy (Dispersalloy®) was chosen as a control material. Cylindrical specimens (4 mm×8 mm) were fabricated and stored in artificial saliva for 1 week at 37 °C. A custom-made creep testing machine was used to test the compressive creep of each of the materials under specified conditions of stress and temperature (155.5 MPa and 37 °C, 155.5 MPa and 55 °C; 36 MPa and 37 °C; 36 MPa and 55 °C) for 24 h, after which the strain recovery was recorded over a period of 24 h.

Results. One-way ANOVA and Fisher’s test showed no significant differences in creep and recovery strain behaviors between ALERT and SureFil for each test condition (P>0.05). However, for residual strain, there was a highly significant difference between Dispersalloy® and each of the packable composites (P<0.01), but no significant differences between the composites themselves (P>0.05). ALERT and SureFil had the lowest creep strain (1.91±0.59% and 1.96±0.36%, respectively) while Solitaire® showed 6.09±0.26% creep strain at 155.5 MPa and 37 °C.

Significance. The low creep and residual strain values of ALERT and SureFil compared to Dispersalloy® amalgam suggest that these packable composite resins are suitable for restoring stress-bearing areas because of their ability to withstand viscoelastic deformation better than amalgam, over extended time periods, even under high load and temperature.