When we got serious about turning our really-really-natural toothpaste idea into Earthpaste, we learned a new word: dentifrice. (Well, one or two of us already knew the word, but the rest of us, the ones who enjoyed normal childhoods, learned it only recently.) Dentifrice is the technical, old-timey term for any paste or powder used for cleaning teeth. In other words, it’s toothpaste.
In a hurry? Short answer: Earthpaste has an RDA score of 105.
But if you’re not in a hurry, you should read the post! We speculate on the tooth fairy’s earning power and explain why toothpaste pH matters.
Every toothpaste, whether you call it dentifrice, or Earthpaste, or bright-blue-sparkly-gel, goes through standard testing to establish how abrasive it is. The test works more or less like this: a person wearing rubber gloves and science-lab goggles grabs a human tooth that has had its enamel stripped away. (Where do all the teeth come from? We don’t know, but if you’d like to lend realistic detail to your family’s tooth fairy tradition, there is a tale you could weave there. Business-savvy kids will appreciate knowing the possible source of the tooth fairy’s revenue.) Anyway, after the tooth fairy (or someone else) delivers these teeth to the lab and a scientist strips off the enamel, they zap a tooth with mild neutron irradiation before brushing it using a special toothbrush. The rinse water contains radiation brushed from the unlucky tooth, which is measured to arrive at a number called the radioactive dentin abrasion score, or RDA. (Some people call it relative dentin abrasion. Same thing.) Basically, they’re measuring how much of the irradiated dentin winds up in the water after brushing with various brands of toothpaste.
It’s a voluntary program, and some experts have pointed out that RDA scores are rather pointless without also measuring the effect on enamel. That makes sense, since we all have enamel on our teeth when we brush, but RDA has become the standard number, anyway. The American Dental Association recommends dentifrices with RDA score no higher than 250, but we’ve never seen a brand get anywhere close to that high. The highest we know is a super-ultra-whitening formula from Colgate, which has an RDA score of 200. (Plain old baking soda has an RDA of 7.) According to independent lab testing, Earthpaste has an RDA score of 105, which the lab noted, with all the excitement you’d expect from a scientific lab, “is typical of dentifrices on the market today and is well within the accepted limits.”
Some companies have attached a marketing spin to RDA scores, and I suppose you can’t blame them for trying. You might have heard that lower RDA scores are better for your teeth, but if you still have enamel protecting the dentin, it seems like a secondary consideration. A 2004 study showed that low-pH (acidic) dentifrices did cause “an increase in enamel abrasion that was greater than might be expected based on the RDA value.” In other words, if you’re concerned that abrasive toothpaste will affect your enamel, you might do well to find a toothpaste with a high pH.
Oh, and did we mention that the pH of Earthpaste is right around 9.7? I mean, we shouldn’t really boast — we just let nature do her job — but that’s pretty darn high!