Objectives: To evaluate and compare the remineralizing efficacy of calcium carbonate and calcium carbamide containing lozenges on enamel lesion progression in relation to lozenges without active ingredients, using an in vitro pH cycling model. Method: Sound extracted molars were painted with nail varnish, leaving 1mm wide window on buccal and/or lingual surfaces before placing in a demineralizing solution for 96 hours (10ml/tooth) to produce artificial carious lesions 100-120 micron deep. Teeth were longitudinally sectioned (100 micron thick) and randomly divided into 3 groups (n=9). Sections in Group A were treated with calcium carbonate containing lozenges (40 mg calcium carbonate/lozenge) while Groups B and C were treated with calcium and carbamide containing lozenges (25 mg calcium and 20 mg calcium carbamide/lozenge) and lozenges without any active ingredients, respectively. Polarized light microscope and microradiography were used to evaluate lesion depth before and after the 10 day pH-cycle. Each cycle involved three hours of demineralization twice a day with two hours of remineralization in between. A five-minute treatment using lozenge slurry (1 lozenge dissolved in 20ml de-ionized water/section) was given after the first demineralizing cycle and both before and after the second demineralizing cycle. Sections were placed in the remineralizing solution overnight. Results: When compared with mean lesion depth before the treatment, mean lesion depth after the treatment in Groups A and B increased by 16% and 23%, respectively (p > 0.05, t-test), while those in Group C increased significantly by 55% (p < 0.05, t-test). Comparisons made among groups showed that Groups A and B were statistically significant different from Group C (p < 0.05, ANOVA and Bonferroni's tests). Conclusion: Based on the data obtained, both of the lozenges containing calcium carbonate and calcium carbamide had the ability to reduce the rate of lesion progression when compared with the ones without active ingredients.