Semiquantitative Studies of in Vitro Caries by Microhardness Tests

Abstract

THE purpose of the present investigation was to develop a method for measuring the rate of in vitro tooth decay. Since surface softening has been one of the initial signs of in vitro tooth decay, changes in hardness of the enamel surface might be a useful index of the rate of the caries attack. The value of a rapid quantitative method for evaluating anticaries agents is readily apparent. The "artificial mouth" ' has been used in this laboratory to produce in vitro tooth decay, the various lesions produced being indistinguishable from those occurring in vivo. This has been shown by the general similarities ' and by histologic,2 ultraviolet and polarized light3 studies of the lesions produced. The microhardness of intact surface enamel has also been investigated in this laboratory.4 It was shown that intact surface enamel varies in hardness on a single tooth surface as well as from tooth to tooth. The variation in hardness is generally within the range of 250 to 450 Knoop numbers. The inherent variation in hardness of a single surface poses a real problem when