Toothpaste contains small particles, known as abrasives, designed to scrub the tooth surface and remove plaque and surface stains. This mechanical cleaning action is necessary for effective oral hygiene. While some friction is required for cleaning, using a product that is too abrasive over time can lead to the wearing away of tooth structure. Non-abrasive toothpaste, more accurately termed low-abrasivity toothpaste, is formulated to minimize this friction, offering a gentler cleaning solution.
Measuring Toothpaste Abrasiveness
The standard international method for quantifying a toothpaste’s scrubbing power is the Relative Dentin Abrasivity, or RDA, scale. This standardized measurement is determined in a laboratory setting and provides a numerical value for comparison. The test involves brushing a sample of radioactive dentin with a toothpaste slurry to measure the amount of dentin material removed.
A reference abrasive is assigned a value of 100, and all other toothpastes are measured relative to that standard. The resulting RDA score indicates the product’s potential for wear on the softer dentin layer underneath the enamel. Products with an RDA value between 0 and 70 are classified as low-abrasive, making them appropriate for sensitive teeth and daily use.
Toothpastes falling between 70 and 100 are considered medium-abrasive and are suitable for most healthy individuals for routine cleaning. Products with an RDA over 100 are categorized as highly abrasive, often found in formulations marketed for heavy stain removal or whitening. For a toothpaste to be considered safe for lifelong daily use, organizations like the American Dental Association recommend a maximum RDA score of 250.
When Low Abrasivity is Essential
Selecting a low-abrasivity product is important for individuals with specific pre-existing dental conditions or restorations. When gum tissue recedes, it exposes the softer root surface of the tooth, which is covered by cementum and dentin, not hard enamel. This exposed dentin is significantly more susceptible to wear from abrasive particles than the enamel crown, leading to faster structural loss.
Wear on the dentin layer directly correlates with the sensation of tooth sensitivity. The dentin contains microscopic tubules that lead directly to the nerve within the tooth’s pulp. Abrasion that removes the protective dentin surface exposes these tubules, causing pain when teeth encounter hot, cold, or sweet stimuli.
Patients who have invested in cosmetic dentistry must also exercise caution regarding abrasive formulas. Porcelain veneers, crowns, and composite fillings can be microscopically scratched or dulled by highly abrasive pastes. Using a low-RDA formula helps preserve the smooth, glossy finish of these restorations.
Ingredients That Affect Toothpaste Grit
The final RDA score of a toothpaste is determined by the type, concentration, and particle size of the abrasive agents used in the formulation. Common abrasive compounds include hydrated silica, calcium carbonate, and dicalcium phosphate. Whitening toothpastes often use a higher concentration of these ingredients or larger, harder particles to physically scrub off surface stains. This formulation consequently increases the RDA value.
Hydrated silica is widely used because its particle size and shape can be modified to achieve various levels of abrasiveness. In contrast, agents like baking soda (sodium bicarbonate) are naturally mild, registering a very low RDA of approximately 7. Consumers can look for words like “for sensitive teeth” or “gentle cleaning” on the packaging, which often indicate a lower RDA formula. While the precise RDA value is rarely printed on the tube, low-abrasive formulas focus on chemical or enzymatic cleaning actions rather than relying solely on physical scrubbing.