An in vitro model for studying the efficacy of fluoride dentifrices in preventing root caries.

This investigation tested and validated an in vitro model for studying the effects of fluoride on human dentin mineral content and fluoride uptake. Four studies examined the effects of different concentrations of fluoride, established dose-response profiles with NaF and Na2PO3F, and tested commercial dentifrices. A 7- or 14-day cyclic treatment regimen involved four 1-min exposures of sound human dentin specimens to the treatment agents, a 4-hour acid challenge period, and 20 h in human saliva daily. Mineral content was analyzed by image analysis microradiography and fluoride assays were performed using a microdrill biopsy technique. Data from these studies established the ability of the in vitro model to provide reproducible results, to demonstrate significant dose-related differences in the effects of both NaF- and Na2PO3F-containing treatments on dentin fluoride uptake and demineralization, and to detect a fluoride-induced reduction in dentin caries, relative to a nonfluoride control, similar to results established in a clinical trial.