Ultrastructure of salivary calculi

Twenty-one submandibular salivary calculi from 19 patients were examined with the light and electron microscope. Adjacent to the peripheral parts of the calculi metaplastic squamous epithelium or connective tissue was seen in close contact to the mineralized matrix. Disintegrated cellular substances from these tissue components were in some cases found to condense in a peripherally located zone of the salivary calculi. The morphology of the examined salivary calculi varied extensively not only within each calculus but also from one calculus to another. High and low incidence of crystals gave rise to the lamellated pattern. In some cases the crystals were so abundant as to five a dense homogeneous appearance. In the central parts of the calculi spheroid bodies of very low electron density with a size ranging from 1 to 100micrometer were found in an amorphous matrix. The origin of these structures is discussed. In the peripheral parts of some calculi osmiophilic spherical bodies with an electron microscopical appearance similar to lipid granules as well as bacteria of cocci or coliform type were found. Degenerated bacteria might in some cases contribute in forming part of the peripheral organic matrix.