This single-center, randomized, double-blind, three-period crossover in situ study evaluated the enamel remineralization potential and fluoride bioavailability of three dentifrices: a fluoride-free negative control, a positive control with 0.243% sodium fluoride, and an investigational dentifrice containing 0.243% sodium fluoride, 5.0% potassium nitrate (KNO₃), and 20% sodium bicarbonate. Adult subjects wore acrylic palatal appliances containing demineralized enamel specimens for three 7-day treatment periods, each preceded by a 5-day fluoride-free washout. Primary outcomes were percent surface microhardness recovery (%SMHR) and enamel fluoride concentration.