Relative dentin abrasivity
Relative dentin abrasivity (RDA) is a method for measuring the abrasive effect that the components of the toothpaste have on the tooth, particularly on enamel and dentin. It involves using standardized abrasives compared against the test sample.
The determination of this value is done by determining the activity while cleaning worn dentin which is radioactively marked by mild neutron irradiation. The values obtained depend on the size, quantity and surface structure of abrasive used in toothpastes.
Since 1998, the RDA value is set by the standards DIN EN ISO 11609.
Currently, the claim on products such as toothpaste are not regulated by law.
The procedure was later adopted by ADA for measuring of Relative Dentin Abrasion Index. According to the ISO standard, every toothpaste with an RDA under 250 is safe for a lifetime of use.[1]
Details
The procedure is more precise and faster than former methods dependent upon the measurement of the depth of a groove cut into tooth structure. The results are obtained directly in terms of the amount of human tooth structure worn away by a toothbrush and dentifrice abrasive slurry operating at a known, constant brush pressure and a constant stroke speed. The coefficient of variation of the test is 6-7 when 8 replications are carried out, and 10-15 when only duplicates are run as in the usual routine testing. This is one half to one fourth of the variation involved in the depth-of-cut method and results can be obtained with an expenditure of one half to one third of the time of the former method.
References
Relative dentin abrasion method of measurement of dentifrice abrasiveness toward human teeth was described in 1958 by researchers R. J. Grabenstetter, R. W. Broge, F. L. Jackson, and A. W. Radike in their article The Measurement Of The Abrasion Of Human Teeth By Dentifrice Abrasives: A Test Utilizing Radioactive Teeth.