The structure of the human tooth.

Plate I Photomicrographs of the human tooth germ. a. At the cap stage of development. The black punctate material is glycogen. b. At the bell stage of development. c. Undecalcified section illustrating the marked Schiff positivity of the odontoblast cytoplasm during dentinogenesis. d. Undecalcified section illustrating the distribution of alkaline phosphatase. Note the intense enzyme activity in the stratum intermedium and the subodontoblastic layer. The black precipitate in the dentine and enamel is caused by the presence of calcium salts and should be ignored. e. Montage photomicrograph of a tooth germ illustrating the disappearance of glycogen from the ameloblasts with the onset of amelogenesis. Plate 2 Amelogenesis. Diagram based on results of investigation by electron microscopy of enamel-matrix formation in rodents (after Fearnhead, 1958). The human tooth consists largely of dentine. I n the centre of the dentine is a cavity which contains the soft tissue of the dental pulp. The dentine is covered on the outer surface of the root by a thin layer of cementum and the dentine of the crown is covered by a layer of enamel. The tooth is slung in its socket by the fibres of the periodontal membrane which stretch from the bone of the alveolus to the cementum.