As awareness of the importance of personal oral hygiene grows, so too does interest in the ingredients of toothpaste and its other properties, particularly what is known as ‘abrasiveness’. In conversations with our customers, we are increasingly being asked about the so-called RDA value. RDA stands for ‘Relative Dentin Abrasion’ and indicates the extent to which the toothpaste can wear away tooth structure. Read the following article to find out where the name comes from, what the value means and why it should not be the be-all and end-all when choosing a toothpaste.
Abrasive agents in toothpaste
It is probably clear to everyone that toothpaste is indispensable for daily oral hygiene. Thanks to the care ingredients it contains, toothpaste prevents tooth decay and gum inflammation, and removes food debris, plaque and even superficial staining. Its cleaning effectiveness is determined by the so-called abrasive agents in the toothpaste. Whilst these are essential components of toothpaste, they can also play a part in the wear and tear of tooth enamel. The cause of such damage is usually a combination of incorrect brushing technique and higher abrasiveness of the toothpaste, which should be indicated by the RDA value.
The RDA value of a toothpaste
Although the measurement of the RDA value – and thus the abrasiveness of a toothpaste – is, or should be, carried out in accordance with an ISO standard and therefore a prescribed protocol, the values should be regarded as comparative figures. Whilst the measurement procedure is standardised, not all steps are described in detail. For example, the duration of the individual steps may vary, as may the type of brushes used to carry out the test.
To determine the RDA value of a toothpaste, the tooth roots are first irradiated with high-energy radiation, causing the phosphorus atoms in the tooth tissue to become radioactive. This process is necessary for the subsequent measurement. The irradiated tooth roots are then secured in a type of brushing machine and brushed with both a standardised reference paste and the toothpaste being tested. The amount of tooth substance removed is determined by measuring the radioactivity in the toothpaste foam. The higher the radioactivity, the more tooth substance has been removed; in other words, the greater the abrasiveness. To obtain the numerical value, the value for the standardised reference paste is set at 100, and the abrasion of the test toothpaste is expressed as a percentage of this standard value. This percentage is then the RDA figure. So, if the toothpaste has an RDA value of 50, this means that it is only half as abrasive as the standard toothpaste used.
The following table, which compares the key parameters of RDA measurements in Indiana, USA, and in Zurich, Switzerland, illustrates just how different the parameters – and consequently the results – of RDA measurements can be:
Source: PROPHYLAXEdialog, special edition on RDA
Furthermore, the RDA value is usually not printed on the packaging anyway, or there is no indication of which laboratory measured it. The RDA value can therefore only be a guide and should not be the sole criterion when choosing a toothpaste. In general, toothpaste with an RDA value of up to 170 (RDA Indiana) is suitable for daily use.
RDA values are not the be-all and end-all
Apart from the ambiguity of RDA values, it is worth noting that damage to the teeth is very rarely caused by an abrasive toothpaste alone. Incorrect brushing technique, e.g. vigorous scrubbing whilst brushing, or brushing immediately after consuming acidic foods, or even the use of a hard toothbrush are factors that should not be underestimated when it comes to damage to tooth structure. Furthermore, toothpastes in the EU are subject to the Cosmetics Regulation and, when used as intended, must not be harmful to health.
If an RDA value is printed on your toothpaste, a maximum value of 100 is the recommended limit for healthy, undamaged teeth. If you are looking for a toothpaste with a lower RDA value, please contact us. However, as a general rule, you won’t find anytoothpaste in our online shop that isn’tsuitable for twice-daily use.