In vitro study of the penetration of three bacterial strains into root dentine.

The purpose of this study was to assess in vitro migration of the following three bacterial species into dentinal tubules: Streptococcus sanguis, Actinomyces naeslundii and Prevotella intermedia. Twenty-seven bovine incisors were randomly divided into three groups. Only the root dentin was used for the experiment. Within each group, the nine incisors were sectioned into 36 dentin blocks that were incubated with one of the tested bacterial suspensions. Twelve samples were taken after 10, 20, and 28 days. Half the samples were observed with scanning electron microscopy and the others with light microscopy after standard histologic procedures, and the depth of bacterial penetration was measured. Analysis of the examinations showed that whatever the technique used, only one strain on this experimental model migrated into dentinal tubules. S. sanguis was observed at a depth of 792 microns, but no migration was observed for either A.naeslundii or P.intermedia. The differences in migration of the bacteria tested appear to be related to their morphologic factors and cellular arrangement.