Light- and electron-microscopic study of the microbial deposits present on the tongue and dentition of macropods.

The dental deposits in the kangaroos and wallabies were similar to human calculus with lysed bacterial cell remnants embedded in previously mineralized areas. The surface of the microbial deposits in contact with the enamel showed: (a) triangular structures 3-5 micron deep and 4-5 micron wide at their base repeating every 4 or 5 micron which probably occupied the remnants of Tomes processes which in macropods do not flatten out; (b) irregular, short (1 micron) projections that probably occupied the inter-prismatic areas. Few organisms were observed on the anterior or dorsal surfaces of the tongues but on the posterior region there was abundant microbial colonization. Large amounts of extracellular matrix were preserved using a fixation technique designed to minimize the loss of water-soluble material. Bacteria were arranged perpendicular to the epithelial cell surfaces and were present on either surface of desquamating epithelial cells. Aqueous fixation erroneously suggested that inter-bacterial and bacterial-epithelial cell adhesion was primarily by fine fibrillar strands.