Experimental Caries and Gingival Pathologic Changes in the Gnotobiotic Rat

¹ National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland

Germ-free rats maintained on a coarse-particle, high-sugar diet did not develop dental caries. Extensive cavitation of the molar teeth was observed in gnotobiotic animals inoculated with a single strain of an oral streptococcus isolated from the rat and maintained on the same diet. The carious lesions in the inoculated animals closely resembled those seen in conventional (non-germ-free) rats receiving the same diet. Histologic studies of the oral tissues of the germ-free animals revealed typical foreign-body reactions and ulceration associated with hairs imbedded in the gingival papillae. In the inoculated animals, infected intrapulpal abscesses resulted from the extensive carious process, but the superficial gingival tissues did not become infected.

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