Abstract
Little information is available on the pathogenesis of fluorosis during the fetal and initial postnatal period. In the present study, female rats received 0 (control), 7 or 100 ppm of sodium fluoride in drinking water, one week before breeding and throughout gestation and nursing periods. The hemimandibles of the offspring were collected at 0, 7 and 14 days of postnatal life (n = 5) and processed for morphological analyses by light and electron microscopy, immunohistochemical analysis for amelogenin and morphometric study of enamel matrix and ameloblasts of incisors. The results showed a decrease in matrix production at the secretory phase at all study periods for the 100 ppm group. In this same group, the secretory ameloblasts showed reduction of enamel matrix secretion, disorganization of mitochondrial crests, large vacuoles at the apical portion of the cytoplasm, retention of intracisternal material and dilatation of some cisterns in the rough endoplasmic reticulum. In the groups of animals aged 7 and 14 days, analysis of variance showed significant reduction (p<0.05) in cytoplasmic volume of 23.80% and 24.75%, respectively, in relation to the control group. The smooth-ended maturation ameloblasts exhibited a large number of vacuoles with electron-dense endocytic matrix, suggesting a delay in the resorption process. Immunohistochemical analysis showed no difference in the intensity and labeling pattern of the enamel matrix in any study group. Interestingly, in offspring at the age of 14 days for the 7 ppm group, there was an increase in the matrix length at the secretory phase. Therefore, part of the excessive dose of sodium fluoride given to the mother in drinking water can reach the offspring through the placenta and mother’s milk, causing morphological changes in ameloblasts and suggesting a reduction in secretion and a delay in matrix resorption.
Highlights
Chronic and acute doses of fluoride have been shown to induce changes in the ultrastructure of ameloblasts of rats, such as atrophy of the distal portion, mitochondrial dilatation, distension and increase in secretion material in the endoplasmic reticulum, 11,24 accumulation of light vacuoles[11,19,29] and dark bodies in the cytoplasm, increase of secretion granules at the apical portion, fragmentation and reduction of Tomes’ processes
Studies on cultured ameloblasts in vitro indicate that the excess of fluoride can cause a stress in the rough endoplasmic reticulum (RER), changing the protein synthesis[12] or interfering with the ameloblast cytoskeleton, damaging the synthesis as well as the resorption of enamel proteins[13]
Immunohistochemical Results for Amelogenin The morphological aspects observed by light microscopy in animals at 0, 7 or 14 days, whose mothers received 0, 7 or 100 ppm of fluoride in drinking water, were similar
Summary
Chronic and acute doses of fluoride have been shown to induce changes in the ultrastructure of ameloblasts of rats, such as atrophy of the distal portion, mitochondrial dilatation, distension and increase in secretion material in the endoplasmic reticulum , 11,24 accumulation of light vacuoles[11,19,29] and dark bodies in the cytoplasm, increase of secretion granules at the apical portion, fragmentation and reduction of Tomes’ processes. Studies on cultured ameloblasts in vitro indicate that the excess of fluoride can cause a stress in the rough endoplasmic reticulum (RER), changing the protein synthesis[12] or interfering with the ameloblast cytoskeleton, damaging the synthesis as well as the resorption of enamel proteins[13]. Most of these studies have been performed on adult animals. Further morphological information is necessary to explain the influence of fluoride on amelogenesis during gestation and nursing phases
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