The aim of this study was to investigate retention of composite fissure sealant polymerized with standard and soft-start technique after a three year clinical trial. One hundred teeth were divided into two groups (A&B) of teeth and sealed with composite material (Visioseal, 3M Espe) using split mouth design. Sealants were polymerized using standard (Group A) and soft-start (Group B) techniques with commercial polymerization unit (Elipar Highlight, 3M Espe). Retention rate in Group A was 72%. In 14 teeth sealant was partially or completely missing. Group B showed retention rate of 80%. Sealant was partially or completely missing in 10 teeth. Six new caries lesions in Group A (3) and B (3) were detected. Mann-Whitney test did not reveal significant differences between the polymerization techniques. After three years complete retention of sealants, regardless of the group, was 76% (76 teeth) with six new caries lesions. Soft-start polymerization showed a comparable retention rate as the standard polymerization technique.