Studies on dental and periodontal conditions in normal mice and mice with genetic disorders. I. The effect of a hard diet or a soft sucrose-rich diet in the absence or presence of Streptococcus mutans in the normal (non-gnotobiotic) mouse, strain C57BL/6J.

Periodontal bone loss and caries development were studied in 45 pigmented mice of the C57BL/6J strain. At the age of 22-30 days the animals were divided into three groups. After 4.5 months one group, which received a hard pellet diet, presented no caries lesions. A second group, which received a soft sucrose-rich diet, had only 2 superficial caries lesions. The animals of the third group, finally, which also received a soft sucrose-rich diet but in addition were exposed to Strep. mutans, had all decayed teeth with only one exception. From this single mouse, Strep. mutants was not recovered. By using a scoring system for periodontal bone loss it could be shown that mice infected with Strep. mutans presented an increased distance between the cemento-enamel junction (CEJ) and the alveolar crest compared with non-infected mice receiving the same soft sucrose-rich diet. Mice kept on the hard pellet diet showed an even greater distance between CEJ and bone crest. This increased distance is suggested to be a result of both increased periodontal bone resorption and of an accelerated tooth eruption, the later probably due to an increased wear of the teeth, especially in the hard diet group, and a compensating elongation of the roots. The experimental model, using mice infected with Strep. mutans and given a sucrose-rich diet combined with the scoring system presented, is suggested to be useful in the study of the influence of endogenous factors on dental and periodontal tissues.