AN IN-VITRO MODEL FOR ADHESION OF BACTERIA TO HUMAN TOOTH ROOT SURFACES

A model mimicking bacterial colonization of dentine has been developed . It employs uniform particles of pulverized human tooth root tissue i ncubated with radioactively labelled bacteria. After incubation, the n umber of attaching bacteria is quantified. Attachment of Streptococcus mutans UA140, Actinomyces viscosus T14, and Lactobacillus casei 101 w as found to be time dependent and complete within 1-3 h. Dissociation constants (K(d)) of the interactions equalled 2.5 x 10(8) and 1.6 x 10 (8) cells/ml, for Strep. mutans and A. viscosus, respectively. The K(d ) for L. casei could not be determined as attachment was not saturable . The putative tissue components involved in adherence were studied by determining the attachment of bacteria in the presence of competing s trains. The results suggest that Strep. mutans and A. viscosus recogni zed and competed for the same ligand (probably collagen) in the dentin e. L. casei attachment did not compete with the attachment of Strep. m utans and A. viscosus. Attachment of all strains was modified by prein cubation with saliva and varied with bacterial strain and saliva donor .