FACTORS INFLUENCING TESTS ON THE ABRASION OF DENTIN BY BRUSHING WITH DENTIFRICES

¹ Dental Research Department of the Procter and Gamble Company, Ivorydale, Ohio

A procedure is described for testing the abrasiveness of dentifrices by means of machines capable of brushing 8 teeth simultaneously, and a shadowgraphic method for measuring cervical dentin wear. Other equipment was devised for determining whether abrasion takes place on exposed dentin when it is brushed in an occlusalward direction.

(1) The brush itself was found to have insignificant abrasive power, since a dry brush abraded dentin only 1% as much as the average of leading pastes and powders. The wet brush was less abrasive.

(2) When teeth with exposed cementum were brushed in a machine in a direction parallel to their long axis, wear of cementum and dentin was produced on a majority of the teeth, but the average rate of abrasion was less than that found with cross-brushing.

(3) When notched ivory cylinders were brushed with abrasive, little or no wear occurred on the crests of the surfaces brushed, and the maximum abrasion developed in the deepest depressions.

(4) Studies were made to determine the proper concentration of dentifrice for use in testing abrasion. It was found that dentifrices are rapidly diluted during toothbrushing, and a 33% concentration of dentifrice is within the range of dilutions observed in vivo.

(5) Decalcified dentin exhibited about the same resistance to wear by popular abrasive-containing dentifrices as did normal dentin. Although the resistance to wear by a moist brush was decreased, decalcified dentin was worn by the moist brush merely about 7% as much as by solid-containing dentifrices.