Why do swimmers shave their heads (or arms or legs)? They’ve learned a basic and valuable principle – things don’t stick well to smooth surfaces. The smoother the surface, the less sticky it will be. In the case of the swimmer, this lowered stickiness causes reduced friction and increased speeds.
So what does this have to do with my toothpaste, you may well ask. Well, we’d all like our toothpaste to leave our mouth fresh and our teeth shiny. But, we probably also want it to leave our teeth smooth, even if we don’t realize that’s something we’re looking for.
Abrasives in toothpaste can leave the surface of the tooth rough. You may not be able to see or feel the rough surface without a microscope, but it is still there. The problem with that is a rough surface provides a great surface for growing a thick, acidic biofilm.
Biofilm on teeth is made up of bacteria. Acidic bacteria in the biofilm choke out other bacteria. Coincidentally, acidic bacteria in the biofilm on teeth also can cause cavities. Giving these bacteria, which are dangerous to overall dental health, a better growing surface with a rough, abrasive toothpaste, is not a sound formula for long term dental health.
Toothpaste manufacturers add abrasives to their products to make it work more effectively. The rough particles scrub at the teeth to try and remove plaque deposits and surface stains on the teeth. But, as anyone who has scrubbed an enamel bathtub with an abrasive cleanser knows, the cleaning power of an abrasive often takes off some of the desired enamel with the undesired dirt. Dirt gets stuck in the resulting scratches and can cause a cycle of buildup.
The American Dental Association require all toothpastes sold with the ADA Seal of Approval to have a RDA (relative dentin abrasion) value of 250 or less. Still, some studies have shown that the roughness value of the toothpaste, and how smooth it leaves the tooth, is not measured by the RDA alone, and is important to overall tooth health. Toothpastes that leave tooth surface more smooth help teeth last longer.
When choosing a toothpaste, carefully consider how abrasive that toothpaste is and if your teeth can take it. You will be brushing your teeth for a lifetime. Why not choose a low abrasion product (18.5) that will help you keep your enamel smooth and strong?
For a comprehensive list of common toothpaste Relative Dentin Abrasivity (RDA) levels check out this resource.