Aim: The purpose of this study was to evaluate the clinical success of three fissure sealants(FSs) with different contents on primary teeth. Study design: Three FSs were used to seal 150 primary molars in 75 children aged 4-7 years. All FSs were placed on occlusal surfaces in a split-mouth and randomized clinical trial. For patients in Group1,amorphous calcium phosphate(ACP) containing resin-based sealant(RBS)(Aegis) was applied to a primary molar tooth on one side,and non-fluoride RBS(Helioseal) FS was applied to symmetrical molar tooth. For patients in Group2, fluoride-containing RBS(Helioseal F) was applied to a primary molar tooth on one side, and Helioseal FS was applied to symmetrical molar tooth. For patients in Group3,Helioseal FS was applied to a primary molar tooth on one side, and Aegis FS was applied to symmetrical molar tooth. Clinical evaluation of FSs was carried out to assess retention, marginal discoloration, marginal adaptation,and the presence of caries in months 1,3,6,12,18 and 24 after FS application. Results: There were no significant differences for all criteria in groups 2 and 3(p>0.05). In group 1,cumulative success rates according to 24 months' follow-up were statistically insignificant during the comparisons performed in terms of retention, marginal adaptation, and presence of caries(p>0.05). Marginal discoloration was found to be statistically significant(p<0.05). Conclusion: RBS containing ACP or fluoride may be more effective than conventional RBS for caries prevention.