Enamel Protection vs. Abrasivity - A Study of Relevance

Dentifrices with Relative Dental Abrasion (RDA)< 250 are considered safe for daily use. Some researchers believe products with low RDA may be less aggressive on erosively softened enamel. Others believe that once softened, erosively challenged enamel will be removed by any friction, even by the tongue. Objectives: To determine the primary driver of enamel protection benefits: is abrasivity or fluoride (F) salt the more important factor? Methods: Cores of extracted, human enamel were cleaned, ground and polished to provide a virgin enamel surface, soaked in human saliva (pellicle formation), and treated in a 1:3 (product:saliva) slurry of toothpaste representing a range of actives/RDA values [SnF2(RDA~150), NaF#1(RDA~100), NaF#2(RDA~50)]. Specimens were subjected to dynamic pH cycling conditions including exposure to multiple 1%citric acid challenges over a 5-day period. Treatment slurries and saliva baths were constantly stirred to ensure a steady flow, representing repetitive challenges to the enamel by a combination of common dietary acid and abrasive elements. The study was run in duplicate to test model reproducibility. Results were averaged. Results: The product with RDA~150 provided significant (p=0.05,ANOVA) protection against damage (8.0um of surface loss), with lower RDA products (RDA~50 or 100) showing no significant differences between them in their ability to protect enamel against damage (27.3 and 25.4um of surface loss, respectively). It is important to note the active F species in the RDA~150 formulation was SnF2. SnF2 provides significant protection against erosive acid damage by forming a protective barrier layer on the enamel surface, protecting against external challenges. Conclusions: These results indicate: 1)the model is reproducible; and 2)the primary driver for enamel protection benefits is more likely the particular F salt, rather than RDA of the formulation. Under the conditions of these studies, SnF2 provided superior protection against acid mediated enamel tooth surface loss.