Electron microscopic visualization of proteoglycans in rat incisor predentine and dentine with cuprolinic blue.

Cuprolinic blue in a MgCl2-critical electrolyte concentration solution allows a larger surface representation of proteoglycans than other methods. Glycoaminoglycans in predentine were ribbon-like structures 14 nm thick and 60 nm long, with radiating filaments (3-4 nm) located in spaces between collagen fibres. Glycoaminoglycans and collagen together displayed longitudinal and orthogonal relationships. The ground substance was slightly electron dense. In dentine, the precipitate was less in quantity and consisted of rounded granules (15 nm in diameter, and filaments/3 nm in width) closely associated with the surfaces of collagen fibres.