Validation of an in vitro model to estimate the amount of fluoride released from toothpaste during toothbrushing

Toothpastes should ideally release most of their fluoride during toothbrushing; however, no clinically validated model currently exists to measure this release. In response, we developed an in vitro model to assess fluoride release from toothpaste, which was validated by comparing it to fluoride levels in saliva during toothbrushing. A crossover in vivo study was conducted with three participants, who brushed their teeth using one Na2FPO3/CaCO3 toothpaste (1450 ppm F) and two NaF/SiO2 toothpastes (1100 or 1450 ppm F). Fluoride release was measured in both in vivo and in vitro experiments using a fluoride ion-selective electrode. The in vitro test involved mechanically agitating three toothpaste samples, while rheological properties were evaluated using a rheometer to determine viscosity and hysteresis area. The in vivo test was conducted by the participants using a standardized toothbrushing technique. Linear regression analyses were performed to examine the relationships between in vivo and in vitro fluoride release, as well as viscosity metrics. A significant linear relationship was found between in vivo and in vitro total soluble fluoride (TSF = ions F- + FPO3 2-) release, as well as between in vivo TSF release and up-shear viscosity. These findings suggest that our validated in vitro test can effectively estimate fluoride bioavailability from toothpaste during toothbrushing in real-world scenarios.