The subject of the study was the clinical analysis of six different sealing materials over a 12-months period. It was necessary to prove the clinical success of sealing with flowable composite with the use of adhesive system and preventing effect of sealants on caries developement. Our study included children aged from 6 to 15, and we sealed 326 teeth with materials from the group of flowable composites in combination with adhesive system (Admira Bond+Admira Flow, Excite+Tetric Flow) and other sealing resins (Teethmate F1, Admira Seal, Helioseal Clear Chroma, Fissurit FX). Over a 12-months period, the total retention was 83.3% (Tetric Flow), 81.5% (Admira Seal), 81.5% (Fissurit FX), 76.4% (Teethmate F1), 75.9% (Helioseal Clear Chroma) and 74.6% (Admira Flow). Only 5 molars (1.5%) developed clinical caries, so fissure sealing has showed to be an excelent prevention of occlusal caries. Flowable composites used with adhesive system are equal to other sealing materials. Sealing materials show great and durable preventive effect against caries development in the fissure system. Since there are many different sealing materials, adhesives, flowable composites on the market and many different pretreatments of the enamel, future studies are necessary and should have an aim to investigate the best technique and material for fissure sealing.