What do the ppm and RDA numbers on toothpaste mean?

Ever flip over a toothpaste box and see “ppm” or “RDA” printed next to numbers you don't recognize? They might seem unnecessary or even confusing, but they're there for a reason. Parts per million, or ppm, tells you the amount of fluoride in a toothpaste. RDA, or relative dentin abrasivity, is a lab rating of how abrasive the toothpaste is on dentin, the layer under your enamel. These numbers can help you compare products, but your cavity risk, sensitivity and brushing habits matter too. 

What you will learn in this article: 

• Parts per million (ppm) shows the concentration of fluoride in toothpaste. 

• Most over-the-counter fluoride toothpastes have 1,000 to 1,500 ppm, while prescription options have 5,000 ppm. 

• RDA measures how abrasive a toothpaste is on dentin in a lab test. 

• Children need only a small amount of fluoride toothpaste to help lower the risk of fluorosis. 

If the numbers on your toothpaste leave you unsure, schedule an appointment with an Aspen Dental provider. Your care team can help you find a toothpaste that fits your teeth and gums. 

What does ppm mean on a toothpaste label? 

On a toothpaste label, ppm shows the concentration of fluoride. A higher ppm means more fluoride, but the highest number is not the right choice for everyone. 

The American Dental Association (ADA) notes that most over-the-counter fluoride toothpastes in the U.S. contain 1,000 to 1,500 ppm. Dental providers may prescribe a stronger toothpaste with 5,000 ppm.¹ 

Why does fluoride strength matter? 

Fluoride helps put minerals back into enamel that has started to weaken. This may stop or reverse very early tooth decay before a hole forms. It also toughens the tooth's outer layer against acid and can slow down the bacteria that form plaque.¹ 

Your dental provider can help decide whether regular fluoride toothpaste is enough or whether you need a prescription-strength option. 

Can too much fluoride cause problems? 

The main concern for young children is dental fluorosis, which can develop while permanent teeth are still forming. The Centers for Disease Control and Prevention notes that once this enamel has finished forming, usually around age 8, older children, teens and adults cannot develop fluorosis. Most cases in the U.S. are mild and only change how the teeth look. 

Children younger than 3 should use a smear of toothpaste about the size of a grain of rice. Children ages 3 to 6 should use a pea-sized amount. Help young children brush and remind them to spit out the toothpaste.² 

What is the RDA number, and why does it matter? 

RDA stands for “relative dentin abrasivity.” It is a lab scale used to compare how abrasive toothpastes are on dentin, the softer layer under your enamel. The test uses a reference material with a value of 100. A higher number means the toothpaste was more abrasive in the test, but it does not predict exactly how much wear you will have.³ 

What RDA score is safe, and is lower always better? 

A toothpaste with an RDA of 250 or less meets the ADA’s abrasivity limit. Every toothpaste with the ADA Seal must stay within that limit. With proper brushing, toothpaste in this range is expected to cause only a small amount of dentin wear and almost no enamel wear over a lifetime. 

A lower number is not automatically safer. RDA scores below 250 are not meant to prove that one accepted toothpaste is safer than another. If you have sensitive teeth, exposed roots or gum recession, ask your dental provider which formula fits your needs.³ 

How do you use both numbers when picking a toothpaste? 

Start by checking the fluoride concentration. For cavity protection, an ADA Seal is another helpful sign that the toothpaste has met the organization’s standards. Then consider your own needs instead of simply choosing the highest ppm or lowest RDA. 

• For most adults, an over-the-counter fluoride toothpaste is a practical starting point. 

• If your dental provider prescribes 5,000 ppm toothpaste, follow the directions and do not share it with anyone else. 

• If you have sensitive teeth, exposed roots or signs of wear, ask which ingredients and formula may help. 

• For children, use the right amount for their age and watch them while they brush. 

Some people also compare fluoride toothpaste with products that use hydroxyapatite-based ingredients. Your dental provider can explain how those options differ and which one makes sense for you. 

You do not have to sort through all the numbers alone. Reach out to your dental provider to discuss your cavity risk, sensitivity and daily oral care. 

What do the ppm and RDA numbers on toothpaste mean? FAQs 

Still have questions about toothpaste ppm and RDA numbers? These answers cover a few common concerns. 

Does whitening toothpaste have a higher RDA than regular toothpaste? 

Not necessarily. Whitening toothpastes work in different ways: Some use mild abrasives to buff away surface stains, while others use peroxide instead. Since RDA measures abrasiveness specifically, only the abrasive-based formulas would tend to affect that number. Check the product information or look for the ADA Seal rather than assuming every whitening toothpaste is more abrasive.³ 

Where can I find a toothpaste’s RDA number? 

If the RDA number is not printed on the tube or box, check the manufacturer’s website or contact the company. The ADA Seal is another quick way to know that the toothpaste meets the RDA limit described above. 

Are fluoride-free or “natural” toothpastes effective without a ppm number? 

A fluoride-free toothpaste will not list a fluoride ppm because it does not contain fluoride. However, “natural” does not always mean fluoride-free, so check the active ingredients. A toothpaste without fluoride does not provide fluoride’s cavity-prevention and remineralizing benefits. 

Does brushing harder change a toothpaste’s RDA? 

No. RDA is a fixed lab rating, so brushing pressure does not change the number. However, too much pressure can still irritate your gums and contribute to tooth or root wear. Use a soft-bristled toothbrush and gentle pressure. 

Sources 

¹ American Dental Association, Library and Archives: “Fluoride: Topical and Systemic Supplements.” https://www.ada.org/resources/ada-library/oral-health-topics/fluoride-topical-and-systemic-supplements 

² Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Oral Health: “About Dental Fluorosis.” https://www.cdc.gov/oral-health/about/about-dental-fluorosis.html 

³ American Dental Association, Library and Archives: “Toothpastes.” https://www.ada.org/resources/ada-library/oral-health-topics/toothpastes