RESUMO
Earlier studies have shown that a single high dose of fluoride induces subameloblastic cysts separated by morphologically unaltered ameloblasts in the developing rat molar. In the present investigation, the ultrastructure of both the ameloblasts forming the cystic wall, and the cells within the cystic lumina were studied by means of transmission electron microscopy. It was shown that 24 h after fluoride injection the ameloblasts of the cystic wall showed various degrees of cytoplasmic and nuclear alterations. Some cells displayed signs of necrosis as indicated by condensation of the chromatin. The cytoplasmic changes varied from altered organelle morphology to fragmentation and almost complete shedding of the whole cytoplasm. In the ameloblasts of the cystic wall secretory products accumulated intracellularly, in distended rough endoplasmatic reticulum, in vesicles of the Golgi region and extracellularly between ameloblasts as well as between cells in the stratum intermedium, indicating an altered matrix secretion. Electron lucent material, cell and cell fragments were found in the cystic lumina, the two latter apparently originating from the ameloblastic layer. The degenerative changes seemed to follow the normal pattern of cell degeneration.
Assuntos
Órgão do Esmalte/ultraestrutura , Fluoretos/efeitos adversos , Cistos Odontogênicos/induzido quimicamente , Germe de Dente/ultraestrutura , Ameloblastos/efeitos dos fármacos , Ameloblastos/ultraestrutura , Animais , Citoplasma/efeitos dos fármacos , Citoplasma/ultraestrutura , Órgão do Esmalte/efeitos dos fármacos , Feminino , Masculino , Cistos Odontogênicos/ultraestrutura , Ratos , Ratos EndogâmicosRESUMO
Rats were given a single high dose of fluoride at the age of 5 days and killed after 24 h, 10 or 15 days. The maxillary first molars were prepared for scanning electron microscopic examination. It was concluded that a single dose of fluoride, preferentially affecting ameloblasts with a high secretory activity, leads to the formation of subameloblastic cysts and enamel hypoplasias covered with granular deposits.
Assuntos
Hipoplasia do Esmalte Dentário/induzido quimicamente , Esmalte Dentário/ultraestrutura , Dente Molar/ultraestrutura , Cistos Odontogênicos/ultraestrutura , Fluoreto de Sódio/efeitos adversos , Ameloblastos/efeitos dos fármacos , Ameloblastos/ultraestrutura , Animais , Esmalte Dentário/efeitos dos fármacos , Hipoplasia do Esmalte Dentário/patologia , Microscopia Eletrônica de Varredura , Dente Molar/efeitos dos fármacos , Cistos Odontogênicos/induzido quimicamente , Ratos , Ratos Endogâmicos , Erupção DentáriaRESUMO
Many substances have been found to cause enamel disturbances in toxic doses, and it has been postulated that these disturbances are linked to the formation of sub-ameloblastic cysts. In the present investigation, fluoride-induced sub-ameloblastic cysts in developing rat molars were related to fluoride dose, age of the animals, and the plasma fluoride level. The sub-ameloblastic cysts, which developed predominantly towards the end of the secretory stage of amelogenesis, appeared shortly after fluoride administration and regressed within 3 days. Hypoplasias and internal defects were found in the enamel under the disturbed ameloblast layer. The highest plasma fluoride levels were found in the youngest animals 24 h after injection. The frequency and size of the sub-ameloblastic cysts were clearly related to the fluoride-dose and age of the animal and, subsequently, to the plasma fluoride level.
