From the basic, white toothpaste of yesteryears to the specialised cavity- and plaque-control ones, toothpastes have come a long way. Scientists at the Fraunhofer Institute for Mechanics of Materials IWM in Halle, Germany, have devised a new technique to determine the cleaning potential of toothpastes. Ishita Das talks to Andreas Kieskow, the lead researcher, on the use of this new technology
Toothpaste is meant to protect the teeth. How can it be harmful?
The very substances in toothpastes that clean the teeth may also damage them. For example, abrasives or particles like silica, alumina and carbonates, that are added to toothpastes to remove plaque, may also erode the teeth surface. Damage can be minimised by monitoring the factors that influence abrasivity or the degree of erosion caused by the toothpaste. It depends on the amount and size of abrasive particles in toothpaste, hardness of these particles, toothbrush bristle shape, contact area between toothbrush and the teeth and force of brushing.
How is toothpaste abrasivity measured?
Conventionally, RDA (radioactive dentin abrasion) is calculated to measure the damage to dentin, the soft layer under the enamel in a tooth, during brushing. For this, dentin samples labelled with a radioactive substance are brushed with the toothpaste to be tested. Whatever amount of dentin is removed from the teeth due to abrasion is retained in the tooth paste slurry as radio-labelled particles. Intensity of radiation from these particles gives the RDA value. Higher the RDA more is the abrasion. Toothpaste brands often claim “intensive cleaning”; this usually means a higher RDA.
How is your method different?
Our method measures the abrasion of enamel, the outermost layer of teeth, instead of dentin. Unlike dentin, enamel does not regenerate and therefore any damage to it is permanent. We follow a tribological approach, which involves using friction, lubrication and wear and tear of interacting surfaces to measure tooth abrasion. No previous study has taken friction into account to study the effect of bristle and toothpaste movement on enamel.
Can this technique help develop better oral hygiene technologies?
We hope our procedure helps us better understand the mechanisms that occur during toothbrush bristle movements on tooth surface. Assessment of factors that influence this, like shape of the filament tip and the resulting contact area, would also be possible.
Have you found any toothpaste brand to be better than others?
We do not aim to categorise toothpastes as better or worse. So far, we have only tested products with known RDA value.