Microbial caries induction in the roots of human teeth in vitro.

Streptococcus mutans GS5, Lactobacillus casei DSM20011 and Actinomyces viscosus T14 produce artificial caries in the roots of extracted teeth. Roots were coated with wax leaving an 8 mm2 window exposed on the buccal surfaces, and then incubated for 8 days in the presence of the test organism, the synthetic medium being changed each day. Samples were then examined by SEM, or microradiographs were obtained from 120 microns sections. The pH at the root surface at the end of the induction averaged 4.43, 5.00 and 5.20, and the lesion depths measured on the microradiographs averaged 121, 83 and 34 microns, for Strep. mutans, L. casei and A. viscosus respectively. This relationship between pH and lesion depth confirms earlier findings. As all of these organisms can produce lesions in tooth structure, elimination of one type would probably not eliminate caries.