Three hermetics are assessed: chemically hardened Delton, light-hardened Estiseal, and composite Evikrol. The study was carried out in 126 children aged 6 years. The decrease of the increment of dental caries depends on the retention of hermetics on the occlusion surface of the teeth, and the efficacy of caries prevention in permanent teeth is much higher if hermetic sealing of fissures and fossae is combined with local fluorine prophylaxis and oral hygiene. All types of hermetics can be used to prevent permanent teeth caries, but chemically hardened ones should be preferred.