Methods: The conventional RDA test (Hefferren, JDR, 1976) was used to compare eight currently or formerly marketed commercial dentifrices with differing abrasive content and/or pH values. Similarly, enamel abrasion (REA) was tested using the same methodology with the exception of enamel substrate and longer brushing time. The dentifrices included those with bicarbonate, dicalcium phosphate, silica, calcium pyrophosphate and silica/alumina combinations as the abrasive systems. The pH values of the dentifrices ranged from 4.3 to 9.2. Means of the individual dentifrice RDA values were compared to the REA values.
Results: The results of the study indicated that all the dentifrices had RDA and REA levels that were within the generally accepted levels of <250 for RDA and <40 for REA. It was shown that dentifrice pH had little effect on RDA values but dentifrices with lower pH values did cause an increase in enamel abrasion that was greater than might be expected based on the RDA value in some cases. Of the dentifrices tested, the use of alumina abrasive had the most dramatic effect on enamel abrasion. Dentifrices with silica/alumina abrasive systems were 1.5X more abrasive to dentin than the reference material but 2X to 3X more abrasive to enamel.
Conclusions: It can be concluded that in some cases, the relative dentin abrasion (RDA) for some dentifrices may indicate a lower abrasion level than the corresponding relative enamel abrasion (REA).