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.

This in situ intraoral appliance (IOA) model evaluates anticaries potential by exposing demineralized enamel specimens to oral conditions while allowing for ex vivo treatment assessments. Subjects wore acrylic palatal appliances containing four enamel specimens covered with steel gauze to promote plaque formation. Each of the three treatment periods lasted seven days and included twice-daily toothbrushing and dentifrice slurry swishing, plus three daily sucrose challenges. A minimum 5-day fluoride-free washout preceded each period. Post-treatment specimens were analyzed for %SMHR and enamel fluoride concentration.

Inclusion Criteria:

• Adults ≥18 years
• Good general and oral health
• Normal unstimulated saliva flow (≥1.5 mL unstimulated saliva in 5 minutes)
• ≥16 teeth and functional maxillary dentition to support palatal appliance
• Agree to abstain from other oral care products and preventive dental procedures during study
• No advanced periodontal disease, no visible untreated caries
• If female, not pregnant or breastfeeding (self-reported)
• No significant oral soft tissue pathology; no peri/oral piercings; no removable partial dentures
• No antibiotics or immunosuppressives within 30 days of screening
• No palatal torus; no medical condition that would interfere with safety
• No allergy or significant adverse events to impression materials, acrylics, or common oral product

Exclusion Criteria:

• Unable to tolerate appliance or comply with procedures
• Oral pathology that interferes with participation
• Use of fluoride toothpaste during washout periods
• Participation in another appliance study within the last 4 week

The sponsor does not plan to share individual participant data (IPD) from this study. Summary results will be provided as required; de-identified datasets or additional supporting documents will not be made available.