BACKGROUND: The authors measured the enamel remineralization of dental interproximal surfaces by a triclosan/copolymer/fluoride liquid dentifrice to test its performance against that of a standard toothpaste. METHODS: In a randomized, crossover, blinded, in situ protocol, the authors fitted 19 healthy adult subjects with mandibular appliances holding bilateral, interproximal bovine enamel slabs. They measured initial abrasion levels and fluoride content. In a two-phase crossover protocol, they evaluated the percentage of surface mineral recovery, or SMR, and fluoride uptake caused by the experimental dentifrice and a fluoride-containing traditional control toothpaste. RESULTS: Abrasion depths were similar and not different statistically (P > .05). The interproximal blocks exposed to the triclosan-containing liquid dentifrice had a mean fluoride uptake that was nearly 100 parts per million (13.1 percent) greater than that achieved with the American Dental Association-accepted control dentifrice. This finding, while not statistically significant, may indicate enhanced performance of the experimental dentifrice because the initial enamel slab abrasion depths were shown to be quite uniform. Moreover, the blocks exposed to the experimental toothpaste had a 49.8 percent SMR, while the positive control blocks had an SMR of only 36.9 percent. This enhanced remineralization performance was statistically significant (P < .05). CONCLUSIONS: This is the first study to show enhanced performance of a triclosan-containing liquid dentifrice in preventing interproximal dental caries. The difference in percentage of SMR was statistically significant and is likely to be clinically relevant. CLINICAL IMPLICATION: The results of this preliminary study offer evidence supporting clinicians' recommendation of the new liquid dentifrice to patients who are prone to developing interproximal carious lesions.