The Pattern of the Mineralization of Enamel

¹ The University of Michigan School of Dentistry, Ann Arbor, Michigan

An investigation using microradiographic, microhardness, microdissection, and microsubstitution techniques was made to gain information about pre- and posteruptive calcification of enamel in 72 human and Rhesus monkey teeth. The following observations were made.

The general pattern of enamel matrix calcification followed and was closely related to the pattern of matrix formation, in disagreement with the theories of two-stage matrix formation-maturation processes.

A band along the dentino-enamel junction reached adult hardness during early matrix formation. The remainder of the matrix exhibited a gradient in radiopacity and hardness from the dentino-enamel junction peripherally which followed the same or a very similar pattern as the incremental pattern of enamel matrix formation. The enamel-rod matrix calcified before the interrod substance, the latter thus presenting pathways for diffusion of tissue fluid containing calcium-phosphate ions, during the mineralization process.

The appearance of radiopacity along the incremental lines was a characteristic of early mineralization. No evidence of a posteruptive increase in mineral content was demonstrated by the microhardness technique. Surface hardness was a characteristic of unerupted as well as erupted teeth.