RDA — the toothpaste number you should know.
Relative Dentin Abrasivity. The one number that distinguishes a gentle daily paste from one thinning your enamel.
Photo: Turgay Koca / PexelsYou read fluoride concentrations on the box. You probably ignore Relative Dentin Abrasivity — RDA. That's the more useful number.
What RDA measures
RDA quantifies how much a toothpaste abrades dentin (the layer under enamel) in a standardized lab test. The scale runs roughly:
- 0–70: Low abrasivity — sensitive teeth, daily safe
- 70–100: Medium abrasivity — standard daily pastes
- 100–150: High abrasivity — many whitening pastes
- 150–250: Very high abrasivity — to be used selectively
- >250: Considered harmful for daily use
The FDA-recommended ceiling for safe long-term daily use is RDA 250. Most dental professionals recommend staying under RDA 100 for daily brushing.
Why this matters
Enamel doesn't grow back. Daily abrasion compounds. A toothpaste at RDA 150 used twice a day for ten years removes measurably more enamel than one at RDA 70. The cumulative effect is barely visible year to year — but visible in the mirror at 50.
This is also why "whitening toothpaste" can be problematic. Many are high-RDA (100–150) silica-heavy formulas that polish off extrinsic stain by mild sandblasting. Used daily, they expose more dentin underneath, which is yellower than the enamel they removed. Net: your teeth read more yellow over years, not less.
Where to find the number
Most brands don't publish RDA. Some do — increasingly the premium ones.
Common toothpastes (approximate RDA, from published independent testing):
- Sensodyne ProEnamel: ~30
- Plain water (for reference): 4
- Most baking-soda toothpastes: 70–90
- Most standard fluoride pastes: 70–100
- Most "whitening" pastes: 100–150
- Crest 3D White Brilliance: ~130
- Many charcoal toothpastes: 150–250
If a brand won't tell you the RDA, assume mid-range (~80–110). Premium oral cosmetic brands publish it.
What to do
- Daily — use RDA <80 for sensitive, <100 for general adult.
- Twice a week — a higher-RDA polishing paste is fine.
- Daily charcoal — stop. Not worth the slow enamel loss.
- Daily "whitening" paste — switch to alternating, or to a low-RDA paste with hydroxyapatite instead.
The cleanest enamel is the enamel that's still there in twenty years.
How RDA connects to peroxide whitening
The two are different mechanisms. Peroxide whitens by oxidizing pigment inside the tooth; RDA-driven whitening pastes work by abrading film on the outside. The first is reversible damage at safe concentrations; the second is irreversible.
If you're choosing a long-term daily toothpaste, ask the brand for the RDA. If they won't share it, that's a flag.
RDA 70 daily. Higher only sometimes.
More: foam vs paste.
Disclaimer. Editorial, not medical advice.