HISTOCHEMICAL STUDIES OF THE PRENATAL DEVELOPMENT OF HUMAN DECIDUOUS TEETH

Publisher Website
Google Scholar
Abstract
Histochemical studies were performed on jaws with tooth germs from 38 human fetuses. The study comprises the period from the downgrowth of the dental lamina until mineralization commences and ranges in crown-rump length from 20 mm to 230 mm (7 1/2 to 26 weeks). The following histochemical reactions were used: (1) 0.1% toluidine blue in 30% ethanol, (2) 0.1% Alcian blue at a pH of 2.7-3.0, (3) 0.1% Alcian blue at pH 1.0, (4) 0.1% Alcian blue at pH 2.7-3.0, followed by ordinary PAS, (5) 0.1% Alcian blue at pH 2.7-3.0 followed by van Gieson staining, (6) PAS for demonstrating glycogen following coating with celloidin. Control experiments using ribonuclease and hyaluronidase as well as fixation experiments were performed. At the bud stage glycogen content is low owing to the mitotic activity. In the cap stage there is increasing glycogen accumulation. In the bell stage the glycogen content of the central cells is reduced pari passu with the accumulation of intercellular substance. Simultaneously with the onset of amelogenesis there is a decrease in the glycogen content of the functioning amelo-blasts, and when the enamel prisms have attained a height of more than 10 [mu] the ameloblasts are devoid of glycogen. This alteration has been related to the onset of protein synthesis. The dental papilla, predentin, dentin, and newly formed enamel give a PAS-positive reaction (glycoprotein). No glycogen is present in the dental papilla or odontoblasts. The acid mucopolysaccharides in the epithelial components of the tooth germ together with the surrounding vessels appear to determine the development of the enamel reticulum. The enamel cord is a delayed stage of this development. While acid mucopolysaccharides became incorporated in predentin and dentin, there are no signs of their incorporation in enamel. The acid mucopolysaccharides in human tooth germs are chondroitin sulphate A or C (possibly both). The dental papilla also contains hyaluronate.