DENTAL CARIES IN RATS PRODUCED BY HARD PILOT BISCUIT

¹ Department of Bacteriology, Columbia University, New York, N. Y.

Seventy-six rats, in 6 groups of 11 to 14 animals, were placed at weaning on (a) a diet of coarsely ground yellow corn, saccharose and spinach, and (b) 5 diets in which the corn was replaced by pilot biscuit of four varieties differing in hardness, the diets also differing in particle size of biscuit. The animals were given the diets for periods ranging up to 100 days. Nine or more of the 12 molars of each animal were examined for caries by means of histological sections.

The group that received coarsely ground corn showed a characteristically high incidence of dental caries, accompanied as in previous experiments by cusp-fracture lesions. Caries lesions were about equally distributed among maxillary and mandibular molars.

Among the rats on biscuit diets, caries occurred in 4 of the 5 groups, but cusp-fracture lesions were entirely absent. The lesions included both fissure caries and proximo-gingival caries, which is described and illustrated. Both types of caries were produced in greatest amount by the harder biscuits, in lesser amount by the biscuit of medium hardness, and not at all by the softer biscuit. Fissure caries was produced in greater amount by coarsely ground than by finely ground hard biscuit, confirming previous findings with raw cereal. On the other hand the highest incidence of proximo-gingival caries occurred on the diet containing hard biscuit finely ground (through 60-mesh), indicating that their primary etiology differs in detail from that of fissure caries.

The relationship of proximo-gingival caries in rats to proximal caries in man is discussed. The findings add important evidence that fissure caries in rats is the true counterpart of fissure caries in man, and in conjunction with other data point to the principle that individual foods, of which pilot biscuit is a type, may be primary causative agents of dental caries in man.