Objective: To investigate the bacteriostatic and cariostatic effect of a novel povidone-iodine/fluoride foam in children at high risk for caries. Method and Materials: Sixty-one 6- to 9-year-old children with at least 1 active dental caries lesion were randomly assigned to 2 groups and treated weekly with either povidone-iodine/fluoride foam (n = 30, experimental group) or placebo fluoride foam (n = 31, control group) for 4 weeks. Stimulated saliva samples were collected for bacteriostatic assessment before each treatment and at 2 and 6 months during the experiment. In addition, laser fluorescence readings of the permanent first molars were taken for the evaluation of cariostatic effect before the treatment and at 2, 6, and 12 months during the experiment. Results: Both groups showed a constant decrease of salivary mutans streptococci over 6 months. Significantly lower laser fluorescence readings were observed for both groups at the 6th month, although with a slight reverse at the 12th month. However, no statistically significant difference was achieved between the 2 groups either for salivary bacteria levels over 6 months or laser fluorescence readings within 1 year. Conclusion: As far as bacteriostatic and cariostatic effects are concerned, clinical application of povidone-iodine/fluoride foam shows no superiority over the regular fluoride foam during a 1-year period. Evidence is still lacking for the combination use of povidone-iodine and fluoride to achieve a better caries-prevention effect in a highcaries- risk population. Schlagwörter: bacteriostatic effect, cariostatic effect, caries prevention, DIAGNOdent, fluoride, povidone-iodine