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Dental Calculus
by Ferdinand Ruzicka

Mature sub-and supragingival dental calculus was collected from 60 adult patients with periodontitis. Without prior decalcification, ultrathin sections of specimens embedded in Epon 812 were examined with a Zeiss EM 109 transmission electron microscope, unstained or stained with uranyl acetate and lead citrate. Sub- and supragingival calcification exhibited only the electron diffration pattern charcteristics of hydroxyapatite (HAp) in all specimens which were sectioned. The absence of whitlockite and brushite crystals is to be discussed.
      Supragingival calcification was divided into extracellular and intracellular types. The extracellular crystalls were of two size classes: large and minute ones. Two types of calcification fronts were found. Intracellular calcification began as minute crystals and could be seen in microorganisms with Gram-positive and -negative cell walls. Extracellular calcification originated within the interbacterial matrix. Subsequently, cell walls of bacteria appeared to calcify. Subgingival calcification was also divided into intra- and extracellular types. The extracellular crystals also occurred in two size classes. They very often appeared as small hexagonal platelets in cross sections of HAp columns.It is suggested that the various forms of crystals were due to differences in the composition of saliva and crevicular fluid.


F.Ruzicka: Structure of sub- and supragingival dental calculus in human periodontitis - An electronmicroscopic study. J. Periodont. Res. 19, 317 - 327, 1984