Explaining RDA

We Are Not Talking About the Recommended Dietary Allowance

From car sales to the military, many trades, businesses and organizations use acronyms and abbreviations to identify certain aspects of their field. It could be an item, report, a department, a manufacturing component, or even a process or method. Common examples are FBI (Federal Bureau of Investigation), DNA (deoxyribonucleic acid), the aforementioned RDA of dieticians, and Scuba (self-contained underwater breathing apparatus).

The same is true in the dental field. For example, the best known acronym indentistry is ADA, used for the American Dental Association. Another acronym that is important for your enamel is RDA, which in dentistry stands for “relative dentin abrasivity.” What is dental RDA, and why is it important?

Getting to the Grit of RDA

In order to improve the effectiveness of toothpaste, manufacturers add abrasive components to help scrape away bacteria and plaque from your teeth and gumline, as well as reduce surface stains from teeth. By removing such items, abrasives help protect against plaque-related issues including gingivitis, tartar buildup, and periodontal disease. In the early 1900s, commonly used abrasives included sand or ground cuttlefish bones. Modern toothpastes use silica, calcium carbonate, alumina, and dicalcium phosphate dihydrate. (Although if your toothpaste uses alumina, studies from Europe suggest that this may be a contributing factor to Alzheimer’s disease.)

Like sandpaper on a piece of wood, however, too much grittiness leads to surface damage, and using too little might not have any effect. The most effective toothpaste has just the right amount of abrasion. In 1948, a study began to measure the amount of abrasion in toothpaste. The study determined that toothpaste abrasion producing less than 1 millimeter (mm) of dentin wear still removed over 90% of surface stains. Dentin is a part of our teeth located beneath the tooth enamel. It’s much softer than tooth enamel, making it an easier test subject.

Setting the Abrasive Standard

Unfortunately, the studies and results were still inaccurate due to a lack of standard measurement. In 1976, the ADA released the RDA method, which became the  standard for laboratory measurement of toothpaste abrasiveness. Considering factors like pressure, time, temperature and humidity, the RDA method calculates the level of abrasiveness for different types of toothpaste. In 1995, the International Standards Organization (ISO) approved this method as a measurement standard.

The ADA and ISO say that a toothpaste with an RDA of 250 or lower is safe for daily use. The number 250 corresponds to 2.5 times the abrasiveness of the reference standard, as set by both organizations. Toothpastes having a higher RDA value than 250 are considered unsafe and are supposed to be pulled from the market. A toothpaste with an RDA value lower than 250 is safe to use but has reduced capability for stain removal.

What the RDA Means for You

Interestingly, natural wear from chewing, and erosion from contact with acidic foods and drinks, all reduce the enamel on your teeth. Comparatively, brushing with toothpaste causes minimal wear on your teeth. Nevertheless, the best way to make sure you’re not causing too much abrasion on your teeth is to get a professional assessment from the Placerville Dental Group. Our dentists examine the surface of your teeth, as well as their alignment and integrity. We go over the findings with you and discuss your current routine of dental care. If any modifications could improve your oral health, we make sure you are fully informed, and we are happy to provide you with tips and suggestions on products.


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