Assessment of creep and compressive strength: bulk-fill versus conventional composites

Abstract

Backgrounds: Creep of composite restorations is affected by their exposure to oral fluids. This study sought to assess the effect of media (water and 75% ethanol) and time storage on creep and compressive strength of bulk-fill and conventional composites. Methods: Twenty-five samples (4 × 6 mm) were fabricated of X-tra fil (bulk-fill) and Estelite Sigma, Grandio SO and Z250 composites (conventional) and divided into five groups (n = 5) according to the storage condition; no storage, 24 h of water storage, 24 h of ethanol storage, 30 days of water storage and 30 days of ethanol storage at 37 °C. Following dynamic creep (1–50 MPa, 0.25 Hz, 30 min, 450 cycles), compressive strength was measured. Results: Estelite Sigma and Z250 conventional composites showed the highest creep (0.0193 mm and 0.0178 mm, respectively) after 24 h of ethanol storage. GrandioSO had the highest creep (0.0148) after 30 days of ethanol storage (P < 0.05). No difference was noted in creep of X-tra fil when stored in different conditions (P = 0.065). Compressive strength following dynamic force application was in the following order: Z250 > GrandioSO > Estelite and X-tra fil. Storage medium had no significant effect on compressive strength. The highest compressive strength was noted in samples stored for 30 days irrespective of the storage medium. Conclusions: Alcohol and water storage increased the creep of conventional composites. Creep of bulk-fill composite was not affected by the storage time or medium. Compressive strength of conventional and bulk-fill composites was not influenced by the storage medium but increased over time.