Reduction in Experimental Rat Caries by Fluorine

Dental research in the field of caries prevention received new impetus when Hoppert, Webber and Canniff experimentally produced dental caries in 90 to 100% of their rats by feeding them a diet, which although adequate nutritionally, consisted mainly of coarse corn particles. Their hypothesis was that the corn particles became impacted in the teeth and produced decay. Lilly obtained a 90% reduction in the incidence of dental decay by substituting commercial casein for the powdered whole milk (20% of the Hoppert, Webber and Canniff diet). The same year, Hodge, Luce-Clausen and Brown found that the commercial casein used by them was contaminated with fluorine (0.2%). It occurred to us that fluorine might be the factor producing the caries reduction in Lilly's experiments. Two major findings in the literature support this contention : (1) clinical observations by Dean and others give evidence of a reduction of caries in areas of endemic fluorisis (mottled enamel); (2) analyses made by Armstrong and Brekhus have shown that sound enamel contains a higher percentage (.0111%) of fluorine than carious enamel (.0069%). Our experiment was, therefore, undertaken to compare the incidence of caries on the Hoppert, Webber and Canniff diet with (a) that on a diet in which “fluorine-free” casein is substituted for the powdered whole milk, and (b) that on the latter diet to which fluorine is added. While this experiment was in progress, Miller reported that adding fluorine or iodoacetic acid to a modified Hoppert, Webber and Canniff diet markedly reduced the incidence of caries. One hundred and thirty-five stock rats at weaning age were divided into 3 groups, separating littermates and segregating the sexes.