This study investigated sealant penetration and dye microleakage of a resin composite system, a compomer system, and a resin-modified glass-ionomer cement in artificially grooved fissures in human molars. Ionosit Seal penetrated 99% of the artificial crevices, whereas Dyract Seal penetrated 97%. The penetration of Helioseal F at 90% was statistically different (P<.0001) from the other 2 materials. Microleakage dye penetration occurred in 22% of the Dyract Seal samples, while it occurred in 5% of Healioseal F and 7% of Ionosit Seal samples. The viscosity and flow properties of the 3 sealants allowed the materials to penetrate the artificial grooves, but they did not seem to affect their sealing capacity.