Efficacy of fluoride toothpaste in preventing demineralization of smooth dentin surfaces and narrow grooves in situ under frequent exposures to sucrose or bananas.

The use of models simulating fissures allows studying demineralization at sites that are most prone to caries in vivo. In practice, most in situ models use flat surfaces. Our objectives were: (1) to compare the demineralizing potential of sucrose solution with that of bananas and (2) to study the effect of fluoride toothpaste on demineralization in situ in an easily accessible site and a plaque stagnation site. Four volunteers wore bovine dentin specimens with narrow grooves and a smooth surface for two 1-week in situ periods, with eight 1-min sugar exposures daily: either by a rinse with 10% sucrose, or by consumption of a piece of banana. Twice daily, the appliance was dipped in toothpaste slurry of a control (fluoride-free) toothpaste at one side and a fluoride toothpaste at the contralateral side. Demineralization was assessed by transversal microradiography. We found no difference in dentin demineralization after frequent exposure to either sucrose solution or bananas. Fluoride toothpaste effectively protected dentin only at the smooth surface. In the grooves, fluoride affected the demineralization pattern; it drove lesions towards the bottom of the groove. We conclude that assessing only smooth surfaces in intraoral tests might lead to underestimated food cariogenicity and to overestimated efficacy of fluoride-containing toothpaste.