Fluoride Dentifrice Protection of Enamel Against Acid Challenge and Softening

Objectives: To assess the ability of fluoride (F) containing dentifrices to protect human enamel against dietary acid challenges. Methods: Enamel protection model (EPM) studies were based on method #33 described in the US FDA testing procedures, with modifications as reported by Newby et al, Abs.1777, New Orleans, 2007. Briefly, human molars were treated with centrifuged supernatants produced from 1 part dentifrice to 3 parts water (weight/weight) for 5 minutes with constant agitation. Pre and post treatment etchings were performed with 1% citric acid pH 3.8, 0.85% tartaric acid pH 3.1 or 6% acetic acid pH 2.4 for 12, 4 or 2 minutes respectively at 37°C with agitation. Etching times were designed to provide a similar pre-etch phosphate concentration for each acid tested. A marketed F dentifrice containing 1150ppm F (NaF) + KNO3 served as the reference control. Performance of two other F dentifrices (1100ppm F as NaF and 1100ppm F as SnF2), were compared for their ability to protect enamel against these three acids that represent acids found in everyday foods and beverages. Results are expressed as a % reduction relative to pre-etch phosphate control values. Results: The 1100ppm F (SnF2) toothpaste resulted in an average % Reduction in Enamel Solubility of 28.7%, while the 1100ppm F (NaF) product provided an average of 15.5% reduction, and the marketed, reference control product containing 1150ppm F (NaF) + KNO3 product delivered a 1.8% reduction in enamel solubility. All differences were significant (p=0.05). Conclusions: This study demonstrated clear differences in performance when comparing the surface protection ability of different F salts, with the 1100ppm F (SnF2) dentifrice providing roughly double the level of protection against a wide range of acid challenges. This work was supported, in part, by The Procter & Gamble Co.