OBJECTIVES: This in vitro study was conducted to investigate the fatigue behavior of several dental restoratives, including composites, glass ionomers and a resin-reinforced glass ionomer. METHODS: Fatigue was imposed under a reverse stress-controlled regimen, following a staircase approach. Samples were stored and tested under both dry and wet conditions. The following parameters were measured and analyzed: Young's modulus, restrained fracture strength, and flexural fatigue limit. RESULTS: As a general trend, all products showed a decrease in Young's modulus following water sorption. For all products except the resin-reinforced glass ionomer, the same trend was seen in the restrained fracture strength. This is, however, no longer valid for the flexural fatigue limit: the trend is steady-state for the glass ionomers, status quo for the resin-reinforced glass ionomer, and all composites tested show a decrease. SIGNIFICANCE: The diversity in structure of both composites and glass ionomers does not allow findings for one product to be extrapolated to other similar products.