The Observation Of Microscopic And Submicroscopic Structure On Incisor Ameloblasts And Expression Of TGF-β1,Smad4 In Ameloblasts Of Coal-burning Dental Fluorosis In Rats

Objective:The study is to observe the change of ameloblast in morphology after SD rats were fed with corn containing overdose fluoride and the effects of overdose fluoride on the expression of TGF-β1 and Smad4 in rat ameloblasts, in order to investigate the mechanism of dental fluorosis in cytology and the control measure of dental fluorosis caused by fluoride in coal initially.Methods:Eighty SD rats were randomly divided into 8 groups (the number of male and female was fifth-fifth in each group):(1)the lowdose fluoride group:they were fed with corn containing 30mg/kg fluoride, supplemented with flour, soybean flour, fish flour, bone flour, wheat and salt;(2)the lowdose fluoride and nutrition disequilibrium group:they were fed with corn containing 30mg/kg fluoride, supplemented with flour, soybean flour, wheat and salt;(3)the mid-dose fluoride group:they were fed with corn containing 56mg/kg fluoride, supplemented with flour, soybean flour, fish flour, bone flour, wheat and salt;(4)the mid-dose fluoride and nutrition disequilibrium group:they were fed with corn containing 56mg/kg fluoride, supplemented with flour, soybean flour, wheat and salt;(5)the highdose fluoride group:they were fed with corn containing 88mg/kg fluoride, supplemented with flour, soybean flour, fish flour, bone flour, wheat and salt;(6)the highdose fluoride and nutrition disequilibrium group:they were fed with corn containing 88mg/kg fluoride, supplemented with flour, soybean flour, wheat and salt;(7)the drinking fluorinated water group:they were received distilled water supplemented with 100ppm fluoride and fed with normal corns, supplemented with flour, soybean flour, fish flour, bone flour, wheat and salt;(8)the normal diet group:they were received distilled water and fed with normal corns, supplemented with flour, soybean flour, fish flour, bone flour, wheat and salt;The rats were killed when dental fluorosis were obviously(about 3 months). The change of morphology and ultrastructure of ameloblasts were observed by means of opticalmicroscope, transmission electron microscope, and immunohistochemical staining was adopted for studying the expression of TGF-β1, Smad4 in ameloblasts of eight groups rat's incisors.Results:(1) HE staining shows that the ameloblast of the normal diet group differentiate from cube-shaped to high column at the position which from root to incide. On the contrary, the ameloblast differentiate from high column to short cube in the maturation stage. The ameloblasts have a well-distributed arrangement and nucleus moving away from the basement membrane. The ameloblast of the experimental group distorted and the hight reduced, vacuolization can be seen, Tomes irregular or disappeared.(2) Transmission electron microscope shows that ameloblast of the normal diet group appear orbicular-ovate nucleus, prominent nucleoli, abundant rough endoplasmic reticulum and ribosomes, matrix vesicle can be seen. In the mid-dose group, the number of organelle decreased, rough endoplasmic reticulum and mitochondria swelling, cristae disappeared, many vacuolus in intracytoplasm, nuclear membrane fragmental and nucleolus condensation. In the highdose group, organelles dissolved,even disappear, mitochondria swelling and vacuolization seriously, the endoplasmic reticulum swell obviously, nuclear membrane rupture, Euchromatin dissolved and heterochromatin aggregation near the membrane, nucleolus disappear.(3)Immunohistochemistry shows that the protein of TGF-β1 and Smad4 both express in cytoplasm. Compared with the normal diet group, they were inhibited in experimental group in each stage, the difference was statistically significant(p<0.05).Conclusion:The morphological of the ameloblasts have changed obviously after the rat was treated with excessive fluoride, such as cells arranged irregularly and became lower, organelles decreased and so on. Lower express TGF-β1 and Smad4 imply overdose fluoride may inhibit theirs secretion and interfere each stage of intracellular signal transduction, then affect the proliferation and differentiation of the ameloblasts, synthesis and secretion of enamel matrix, results in a series of pathological change of dental fluorosis.