Clinical preventive procedures must be done after a risk assessment. One of the risk factors is the occlusal morphology of the posterior teeth. These caries-free fissures must be sealed. This first in vitro experimentation of the study evaluated the microleakage and the penetration depth of three types of materials by Vivadent: Helioseal F®, Tetric®, Tetric Flow®. The teeth were etched with phosphoric acid and bonded using a one bottle bonding in order to determine the best material for the sealing of the fissure. The depth of penetration of fuschine dye as well as that of the tested material was measured with a grid. The results, compared to the depth of the fissures, are expressed in percentage of penetration. The results were as follows: penetration of fuschine dye: 0 % for the 2 composites, 100 % for Helioseal F®; penetration of the materials: 96.90 % for Hélioseal F®, 70.82 for Tetric® and 86.10 for Tetric Flow® (significant difference,Wilcoxon test = 0.0105). In this first in vitro study,Tetric Flow® shows no microleakage and is more efficient when compared to Helioseal F® and Tetric® in obturating deep fissures of non carious bicuspids. The second experiment of the study evaluated the microleakage and the penetration depth of Tetric Flow® when it is bonded by two different methods: Group 1: total etch (phosphoric acid) and Scotch-bond 1® (3M), and Group 2: self-etching primer with Prompt® (Espe). There was no significant difference (p > 0.03) between classical bonding vs self-etching primer. The self-etching primer Prompt® is very efficient vs phosphoric acid in obturating the fissures of non carious bicuspids with Tetric Flow®. It is concluded that for prevention by sealing, using a flowable ceromer (Tetric Flow®) with the self-etching (Prompt®), is a really good technique.