Comparative Caries Experience of Littermate Rats Fed Three Different Cariogenic Rations

¹ Western Biological Laboratories, Culver City, California, and Department of Biochemistry and Nutrition, School of Dentistry, University of Southern California, Los Angeles, California

Studies were conducted to determine the comparative caries experience of littermate rats fed 3 distinct cariogenic rations under conditions in which experimental conditions (i.e., genetic background, diet of the mother during the period of tooth development, the age at which rats were started on the test diets, the duration and method of feeding, and the number of animals per cage) were kept constant as far as possible for all groups. One diet was a highly purified, sucrose-containing ration, similar to Diet 593 of Stephan and Harris; another was a non-heat-processed, wheat-flour-containing ration, similar to Diet 256 of McClure; and the third was a roller-process, skim-milk-containing ration, similar to Diet 635 of McClure and Folk.

Findings on the above diets were contrasted with those observed in littermates fed a non-cariogenic stock ration. The average caries score after 90 days of feeding was 46.8 on the purified, high-sucrose diet; 14.9 on the wheat-flour diet; 3.7 on the skim-milk-containing diet; and 0.2 on the stock ration. On the purified, high-sucrose diet more than 90 per cent of the carious lesions were of the occlusal type, with less than 10 per cent of the smooth-surface variety. On the wheat-flour and skim-milk-containing diets, the majority of carious lesions were of the smooth-surface type. No correlation existed between the microscopic appearance of the thyroid and submaxillary glands and average caries score.

An unexpected finding was the occurrence of a paralytic-like syndrome in rats that were fed the wheat-flour-containing diet for 90 days and were then dropped from a height of 12 inches. Although all rats in this group appeared grossly normal prior to the time they were dropped, an apparent paralysis of both forelimbs and hindlimbs could be induced almost immediately in these animals by dropping them from a height of 12 inches. The affected animals were clearly responsive and were not undergoing seizures. Tactile placing and hopping reactions were lost. A gradual return to normal occurred after 10-15 minutes. No deleterious effects were observed under comparable conditions in rats of other dietary groups.