MICROSTRUCTURE OF THE HUMAN TOOTH

A. THE DENTINOENAMEL JUNCTION

¹ Naval Medical Research Institute, Bethesda, Md., and National Bureau of Standards, Division of the Council on Dental Research of the American Dental Association, Washington, D. C.

The literature concerning the dentinoenamel junction is reviewed and a study of the structure of this region by polarization, fluorescence, microradiographic, and ultraviolet absorption technics is presented.

Adjacent to the dentin at the dentinoenamel junction, low fluorescence, radiopacity, a characteristic birefringence, and low ultraviolet absorption demonstrate a hypermineralized zone 20 to 30 microns thick. This zone generally cannot be seen as a regular, continuous structure.

Adjacent to the hypermineralized zone in the enamel, intense fluorescence, radiolucency, and high ultraviolet absorption characterize a broad zone of hypomineralization.

At the terminations of the dentinal tubules a very thin, strongly ultraviolet absorbing layer is found.

The tuft or whorl is seen to be composed of groupings of interrod material or rod "sheaths." The base of the tuft is fibrillar and elements of it are intimately related to the terminal bifurcations of the tubules.

Most of the rod "sheaths" are discontinuous in the hypermineralized zone although in a few cases continuity with dentinal elements occurs.