INHERITANCE OF SUSCEPTIBILITY TO CARIES IN ALBINO RATS (MUS NORVEGICUS)

¹ Departments of Zoology and Chemistry, Michigan State College, East Lansing, Mich.; and the Department of Biology, Henderson State Teachers College, Arkadelphia, Ark.

1. The conclusion of Hoppert, Webber, and Canniff that a diet of coarsely ground rice, powdered whole milk, alfalfa leaf meal, and sodium chloride will induce dental caries in rat molar teeth, has been repeatedly confirmed.

2. If the rice component of this diet is ground to flour fineness, caries is at least delayed.

3. The time required to develop tooth cavities is not a reliable index of the genotype of the individual rat.

4. A caries susceptible strain and a caries resistant strain of rats have been produced by selection, progeny testing, and close inbreeding. Heredity is therefore an important factor in the development of rat caries.

5. There are reasons for believing that multiple factors are responsible for differences in caries resistance, but further experimental work is required to test this hypothesis, to identify the number of gene pairs, and to discover the physiological and anatomical effects of these genes.

6. A highly susceptible type of rat has been secured which is excellent material for studies on the chemical prevention of tooth decay.