Compressive creep and recovery of light-cured packable composite resins.

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 x 8 mm) were fabricated and stored in artificial saliva for 1 week at 37 degrees 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 degrees C, 155.5 MPa and 55 degrees C; 36 MPa and 37 degrees C; 36 MPa and 55 degrees 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 degrees 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.