A five-factor study was done on human dentin abrasion that involved two abrasives, either alone or in dentifrice form, two brush brands, two brush hardnesses, two concentrations, and two temperatures of testing. The hard brushes caused 3.6 times as much wear as the soft brushes, a greater influence than the abrasives compared. A brush X hardness interaction indicated that there is a wide variation among the stiffness gradings of toothbrushes. Tests run at 37 C were 28% less abrasive than those at room temperature, suggesting a softening of bristles because of the warmer temperature. A highly significant abrasive X concentration interaction showed that dentifrices became more than twice as abrasive on dilution form 100 to 50%, but that abrasives alone did not show such changes on dilution. The second study included two hardnesses, two abrasives, three diluents, four concentrations, and two replicates. An interaction was found between abrasive and diluent, showing that glycerine inhibited abrasion by 88% in comparison with saliva and CMC. A hardness X concentration interaction showed that wear varied widely with concentration for the hard brush but scarcely at all for the soft brush. These findings suggest that abrasiveness of dentifrices depends strongly on testing conditions and that no single set of conditions is suitable for evaluating dentifrice abrasiveness.

A study was conducted to explore the effect of brush brand, brush hardness, and the concentration of abrasive on the wear of human dentin by four dentifrice abrasives. The two hard brushes produced similar and high levels of abrasion, whereas the two medium brushes of the same brands gave dissimilar and lower levels of abrasion. Dilution changed the ranking of two of the four abrasives.

A method has been developed for testing dentifrice abrasiveness which is based on a commercial toothbrush motor that operates a brush with only one or two tufts and on the application of dentifrice to a disk of neutron-irradiated dentin. Greater precision was found when only one tuft was used. The wear by two commercial dentifrices depended on the force on the brush and on the concentration during testing.