A method for measuring the abrasivity of tooth pastes

The abrasive properties of tooth pastes are usually investigated by brushing natural teeth which have been activated by irradiation, and subsequently measuring the radioactivity of the abraded particles (RDA-, REA-values). The standard REA and RDA measurements using actual tooth material represent the practical situation very well, however, the measuring procedure is complicated and expensive. In addition, the measurement technique and the biological variation of individual teeth result in a large scatter of the obtained data. Therefore, another approach was chosen, simulating the tooth by a dental composite filling material and utilizing a test set-up which was developed earlier for measuring the abrasion behaviour of dental materials. This test is based on an arrangement of a brush and a specimen which rotate in opposite directions in a tooth paste slurry under loading conditions (force, velocity, etc.) which are close to tooth cleaning conditions. The material loss is measured by weighing the samples (at least 5) after a well defined cleaning and drying procedure. Various widely used commercial tooth pastes covering a broad spectrum of abrasion levels (i.e. RDA-values) were investigated. The results show a reasonably small scatter (typical standard deviations 10%) and a high reproducibility of the abrasion values. The abrasion caused by mild and abrasive tooth pastes differs typically by a factor 5 - 10. The method seems to be more accurate, faster, easier to perform and less expensive than the abrasion test based on radioactive marking and thus can be a reliable alternative to differentiate between pastes with different abrasivity.