Advances in Dental Research, Vol 3, 188-198, Copyright © 1989 by International & American Associations for Dental Research
Enamel hypomineralization viewed from the pattern of progressive mineralization of human and monkey developing enamel
S. Suga
Microradiograms and their computer-aided image analysis of ground sections
of the developing enamel of human permanent third molars and monkey
permanent teeth (Macaca fuscata) indicate that the mode of progressive
mineralization of enamel is completely different between the matrix
formation and maturation stages. During the former stage, the enamel matrix
is slightly mineralized. During the latter stage, which takes a much longer
period than the previous stage, the increase in the secondary
mineralization takes place first slightly, from the surface toward the
inner layer, and then heavily, from the inner layer toward the surface. The
narrow outer layer mineralizes very slowly during the middle and late
stages of maturation, but finally achieves the highest mineralization of
the entire enamel layer. The very narrow innermost layer mineralizes slowly
without expanding its width. The former three processes seem to be under
the direct control of the ameloblasts. Hypoplastic areas which appear
during the matrix formation stages are not necessarily accompanied by
hypomineralization. Dysfunction of the cells immediately after the
completion of matrix formation appears to cause hypomineralization
throughout the entire width of matrix except for the innermost layer.
Disorders of the cells occurring during the middle and/or the late stage of
maturation--due to chronic metabolic disturbances, such as
fluorosis--induced hypomineralization localized mainly at the outer layer.
The hypomineralized enamel is not necessarily accompanied by hypoplasia.
The process of enamel mineralization is not necessarily fully synchronized
with that of tooth eruption. Therefore, the narrow outer layer, especially
in the fissure and cervical regions, is sometimes hypomineralized even
after the teeth have erupted normally.
