The Crystalinity of Hypomineralized Rat Enamel by Fluoride Administration

Abstract

It has been well known that there are extreme amounts of intercrystalline spaces and large amounts of enamel matrix in fluolosed human enamel. Our previous study discussed the fact that amelogenins in developing fetal enamel matrix protein may have a role in regulating or controling enamel crystal growth. These results positively suggest that amelogenins degradation may be associated with the etiology of fluorosed enamel.
The purpose of this study was to examine the relationship of the crystalinity of fluorosed enamel of rats and the molecular weight of enamel matrix protein. The crystalinity of fluorosed enamel of rats, caused by the ingestion of fluoride containing water was evaluated with the microbeam x-ray diffraction analysis and the molecular weight of enamel matrix protein was examined by SDS-polyacrylamidegel electrophoresis.
The results obtained in the study are summarized as follows.
1) The plasma fluoride level of rats increased linearly with the fluoride concentration in the drinking water.
2) The microradiographs of maturing incisor enamel of the group with 100 ppmF-and 200 ppmF- injected showed diffused radiolucent zone from the subsurface toward the dento-enamel junction. The disturbances in enamel mineralization were most appearent in the 200 ppmF- group.
3) The crystallinity of the radiolucent zone of the fluorosed enamel decreased in both the a and c-axis directions, and particulary decreased more in the a-axis compared with the control.
4) The pattern of the SDS-polyacrylamid gel electrophoresis of the enamel protein in the mature stage showed higher remaining molecular weight of amelogenins in rats in the 100 ppmF- and 200 ppmF- group. These results suggest that in hypomineralized enamel caused by long-term administration of fluoride containing water, the degradation of amelogenin protein was disturbed, and consequently the crystallinity of enamel apatite decreased.