While we’ve all been advised to brush our teeth twice a day, not all toothpastes are created equal– especially when considering different ingredients and how abrasive they could be on our teeth. This is where RDA values come into play– a standardized scale for rating toothpastes based on their relative dentin abrasion.
1: What’s An RDA Ranking And Why It Matters
RDA stands for relative dentin abrasion. Essentially, it offers a standardized scale from 0-250 that can rank toothpastes on their levels of abrasion. Lower numbers mean a toothpaste is less abrasive, and the closer a toothpaste is to 250 the more abrasive it is. Within the scale a ranking of 0-70 generally means low abrasion, 71-100 medium abrasion, 101-150 highly abrasive, and 151-250 being regarded by the FDA as the harmful limit. RDA ultimately matters because a value too high can cut into the enamel– the hard, protective covering of your teeth– and eventually harm the dentin layer of your teeth which protects the tooth’s nerves. The more exposed the nerves become, the more pain and sensitivity you’ll begin to feel.
The RDA scale utilizes the MOHs hardness scale when ranking specific toothpastes which measures a material’s resistance to scratching. However, the MOHs hardness scale is not the only factor that comes into play. The RDA scale takes into account other factors like particle shape and size, pH, chemical composition, and frequency of use. Below is a table summarizing some of the most common toothpastes and their respective RDA values, as well as the FDA and ADA upper limits:
Multiple studies have shown the correlation between higher RDA values and greater dental abrasion.
2: The Ingredients That Play A Role In RDA Rankings
According to the Journal of the American Dental Association (JADA), some abrasive ingredients that are included in toothpastes are hydrated silica, hydrated alumina, calcium carbonate, dicalcium phosphate dihydrate, calcium pyrophosphate, sodium metaphosphate, perlite, nanohydroxyapetite, diamond powder, and baking soda. The most common abrasive ingredients out of this list that are added to toothpaste include calcium carbonate (CaCO₃) and hydrated silica (H₂O₃Si). While some of these ingredients can lead to too much abrasion, the formulation of the toothpaste as a whole really matters because abrasiveness in itself isn’t necessarily always a bad thing– it can aid in polishing our teeth and removing surface stains. This is why the amount of abrasive ingredients added varies depending on the toothpaste’s complete chemical composition and the particle size of each ingredient. A study published in the Journal of Cosmetic Science specifically looked at the two most common abrasive ingredients, calcium carbonate and silica, and whether or not the particle size of each raw material mattered in how abrasive it was. It found that particle size matters because for both ingredients a larger particle size resulted in a greater amount of dental abrasion. Although these abrasive ingredients are important for producing an effective toothpaste, it is imperative that a balance is found when adding these ingredients so that a toothpaste works effectively to clean your teeth while also protecting your enamel and dentin.
3: Why This Matters for Whitening Toothpastes
You may be wondering how this scale affects whitening toothpastes. While it may seem like any toothpaste claiming it can whiten and remove surface stains would necessarily mean a higher RDA value, this isn’t always the case. Although some whitening toothpastes are higher on the scale, others are not and it’s ultimately not a determining factor of RDA value. It all comes down to combination of ingredients. While some studies evaluating the abrasiveness of specific whitening toothpastes found that they did in fact result in more abrasion than regular toothpastes, this was most likely due to the differing concentrations of hydrated silica in the whitening toothpastes as compared to the regular toothpastes.
4: Why Abrasive Ingredients Can Be Necessary
If abrasive ingredients can have such negative effects on our enamel and dentin, why are these ingredients continuously added to toothpastes? An article discussing the role of different ingredients in toothpastes specifically highlights abrasives’ importance in helping remove stains, plaque, and tartar. This is why in limited amounts (and when considering your own personal oral health needs) there are significant benefits to these ingredients in your toothpaste.
5: Conclusion
Overall, it’s important to look into the exact ingredients being added to your toothpaste and, if you’re concerned about damaging your teeth, should always consult a professional dentist. Although some combinations and concentrations of these ingredients can be dangerous, research has shown it can be essential to not avoid these ingredients entirely. What’s crucial is finding the optimal balance of ingredients that will provide you with the cleanest teeth and the least possible damage.
