[Ultrastructural morphological study of supragingival tartar].

Specimens of old supragingival calculus, collected from 5 patients with periodontitis, were examined electron-microscopically. Both intracellular and extracellular calcification were found. Intracellular calcification began as needle-shaped crystals or minute amorphous deposits within microorganisms. Extracellular calcification originated within the interbacterial matrix.