Demonstration of a fluoride dose response with an in situ single-section dental caries model

The in situ dental caries model developed in Glasgow was evaluated by determining whether it could demonstrate a fluoride dose response in a crossover study using 0, 250, and 1,000 ppm F from sodium fluoride dentifrices. In situ appliances, each carrying four enamel sections with multiple artificial carious lesions, were worn by 12 dentate subjects for three 5-week experimental runs, during which they brushed twice daily with a test paste. Mineral changes in the lesions were measured by analyzing microradiographs, using an image analysis system, after 0, 2, 4, and 5 weeks and the rate of change calculated. Two-way analysis of variance showed no significant intersubject effects (for any of the parameters), but demonstrated strong evidence of a linear fluoride dose effect: total mineral loss (delta z) p = 0.0596; lesion body p = 0.0423; surface zone p = 0.0081. However, the exclusion of the data from 1 low-caries (DMFS = 1), high-calculus-forming subject produced even stronger evidence as to the efficacy of this model (delta z p = 0.0226; lesion body p = 0.0164; surface zone p = 0.0081). Hence, these results suggest this model is useful for studying fluoride products according to guidelines of American Dental Association.