The submicroscopic structure of dental enamel

Abstract

In observations made on photomicrographs and x-ray diffraction photographs of human deciduous enamel, it was found that each enamel prism is composed of a multitude of crystallites of apatite which may be divided into 2 groups, so arranged that their hexagonal axes tend to make definite angles with the direction of the prism. The values of these angles are approximately 5 and 40[degree] and the crystallite axes are inclined so as to point to that side of the prism remote from the nearest cusp, the directions being taken away from the tooth. In general both the above groups of crystallites are present in the prism, with the 5[degree] group predominant, although occasionally both groups are equally represented. Sometimes, however, the 40[degree] group is entirely absent. In some cases variations in the degree of perfection of the crystalline orientation within individual prisms may occur, thereby giving rise to the three types of x-ray photograph observed. In other cases, these different types of photograph may be due to variations in prism regularity. The interprismatic substance, like the prism material, usually contains the 5 and 40[degree] groups of apatite crystallites, but nothing can be said as regards the variation in degree of perfection of the crystalline orientation.