DETERMINATION OF SIZE AND SHAPE OF THE APATITE PARTICLES IN DIFFERENT DENTAL ENAMELS AND IN DENTIN BY THE X-RAY POWDER METHOD

¹ The Chemical Department of the Dentistry College and the Chemical Department of the Royal Veterinary and Agricultural College, Copenhagen, Denmark

Particle dimensions in enamel and dentin have not been determined with great accuracy up to now. We have determined the apparent particle size in a few enamel powders and in one dentin specimen and found that there are great differences in particle size in different enamels. Crystallite thickness ranging from some 600 Å in a fine human incisor to some 250 to 300 Å in human molars has been found. Figures for enamel from rabbit and beaver were somewhat lower.

The importance of particle sizes for discussions of enamel formulas is pointed out.

Enamel particles are uniformly developed in all directions; this contrasts with the apatite particles in bone which are elongated in the c-axis direction.

We have noted a curious effect in our enamel diagrams: The line broadening increases more with increasing particle size than expected for an assembly of error-free crystallites of uniform size. In other words, the apparent crystallite size calculated from higher order reflections is lower than that calculated from low-order reflections. This effect has not been explained.

The investigations are being continued.