Objective: To compare the efficacy of a new dentifrice containing 1.5% arginine, an insoluble calcium compound and 1450 ppm fluoride to arrest and reverse naturally occurring buccal caries lesions in children relative to a positive control dentifrice containing 1450 ppm fluoride alone. Study design: Participants from Chengdu, Sichuan Province, China tested three dentifrices: a new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride, as sodium monofluorophosphate, a positive control dentifrice containing 1450 ppm fluoride, as sodium fluoride, in a silica base, and a matched negative control dentifrice without arginine and fluoride. Quantitative Light-induced Fluorescence (QLF) was used to assess buccal caries lesions at baseline and after 3 and 6 months of product use. Results: 438 participants (initial age 9-13 years (mean 11.1 ± 0.78) and 48.6% female) completed the study. No adverse events attributable to the products were reported during the course of the study. The subject mean ΔQ (mm2 %), representing lesion volume, was 27.26 at baseline. After 6 months of product use, the ΔQ values for the arginine-containing, positive and negative control dentifrices were 13.46, 17.99 and 23.70 representing improvements from baseline of 50.6%, 34.0% and 13.1%. After 6 months product use, the differences between the pair wise comparisons for all three groups were statistically significant (p <0.01). The arginine-containing dentifrice demonstrated an improvement after only 3 months that was almost identical to that achieved by the conventional 1450 ppm fluoride dentifrice after 6 months. Conclusion: The new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride provides statistically significantly superior efficacy in arresting and reversing buccal caries lesions to a conventional dentifrice containing 1450 ppm fluoride alone. © 2013 Elsevier Ltd.