THE LOCALIZATION OF POLYSACCHARIDES IN DEVELOPING TEETH

¹ Department of Histology, College of Dentistry, New York University, New York, N. Y.

A histochemical study of the developing tooth has been made with special reference to the localization of polysaccharides in the several components.

Mucopolysaccharide is widely distributed in the several components of the tooth; of especial interest is its gradual increase in intensity in functional ameloblasts and odontoblasts. With the onset of calcification, dentin likewise shows a correspondiing increase in mucopolysaccharide content.

Metachromasia, presumably indicative of acid polysaccharides, is confined almost exclusively to extracellular regions. Intense metachromasia was observed in the ground substance of the dental pulp and of the stellate reticulum of the enamel organ. As enamel and dentin are elaborated, the ground substances of these two tissues exhibit metachrormasia. With the advent of calcification, the initially calcified increments stain orthochromatically (blue). Older, more highly calcified enamel and dentin do not stain with either toluidine or methylene blue. The probable failure of calcified tissues containing acid polysaccharides to stain metachromatically has already been referred to.

Sections of the developing tooth digested with testicular hyaluronidase subsequently show a loss in metachromasia of the ground substance of the stellate reticulum. Failure of this enzyme to alter appreciably the metachromasia of the other components of the tooth indicates that the acid polysaccharide complex of the enamel organ differs from that which is associated with the mesodermal derivatives such as the pulp and dentin.