Working time and setting time of four commercial sealants were investigated by means of a rheometer for composite resins. Temperatures in extracted human tooth were also examined by means of a thermocouple during the setting of sealant brushed into the pit and fissures. In addition, unreacted substances in the cured materials were studied using a high performance liquid chromatography.The working time was 0.52-1.09min at 23°C and the setting time was 0.91-1.38min at 32°C. The temperature of the dentin at a point 1.20mm from the roof of the pulp chamber ranged from 0.18 to 0.21°C, as specimens of each material 0.5mm thickness were cured. The percentages of unreacted substances were calculated as the ratio of the area under the chromatogram curve obtained before and after curing, and these ranged from 19.7 to 45.8 for specimens of the four materials with a thickness of 0.5mm.Probably, temperatures during the setting of the four materials tested had little effect on the damage to dental pulp.