Objective: The purpose of this study was to investigate the influence of tooth-polishing pastes and sealants on values obtained with a caries diagnostic system based on detection of caries-associated fluorescence (DIAGNOdent, KaVo). Method and materials: Ten tooth-polishing pastes and four dentifrices were measured alone, and it was shown that products containing pumice gave high DIAGNOdent values. The deepest occlusal pits of 20 extracted sound premolars (12 unsealed teeth, 8 sealed teeth) were measured before polishing, after rotating-brush polishing with pumice-containing tooth-polishing paste, and after final rotating-brush polishing with water in this in vitro study. In the clinical phase, the deepest occlusal pits of 21 molars and 2 premolars that clinically required application of sealant were measured before polishing, after rotating-brush polishing with one of two pumice-containing tooth-polishing pastes, and after sealant application. All measurements were done five times, and the average values were obtained. Data were statistically analyzed using analysis of variance subsequent to Fisher's protected, least significant difference. Results: Clinical study showed that the value after polishing with either of the two polishing pastes was significantly higher than the value before polishing. Both in vitro and clinical studies showed that the value was increased by pumice-containing paste polishing and rotating-brush polishing with water after paste polishing could not recover the value to the level before paste polishing. Sealant treatment in the clinical study significantly decreased DIAGNOdent values, and the values after sealant application were lower than the values before polishing. Conclusion: Polishing pastes and sealants used in this study could interfere with DIAGNOdent values.