Flexural performance of flowable versus conventional light-cured composite resins in a long-term in vitro study

The purpose of this study was to evaluate the flexural strength, flexural modulus, modulus of resilience, and water sorption of four flowable light-cured composite resins (FCRs). Results were then compared with four conventional composite resins (CCRs) and a minifilled hybrid light-cured composite resin, which served as a control. Twenty specimens were flexural tested immediately after curing, while others were stored in water at 37°C for 1 month, 3 months, 6 months, or 1 year before flexural testing. The 1-year specimens were weight-measured at designated time intervals to examine water sorption. All FCRs, except Point 4 Flowable, showed higher flexural strength values than their CCR counterparts (p<0.05, Scheffé's test). After one-year water storage, the flexural strengths and flexural moduli of FCRs increased 1.5-fold or more when compared with the immediate condition. In most cases, the moduli of resilience of FCRs were higher than those of CCRs. In conclusion, it was found that FCR and CCR with the same brand name had very different characteristics and mechanical properties.