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.
Nordlund AT., Lindskog S: Scanning electron microscopy of fluoride-induced disturbances on the enamel surface of rat molars. ScandJ Dent Res 1986; 94: 185-92.Abstract -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 subamelohlastic cysts and enamel hypoplasias covered with granular deposits.
— 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 ultrastnucture 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 cytopiasmic and nuclear alterations. Some cells displayed signs of necrosis as indicated by condensation of the chromatin. The cytopiasmic 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 ameioblasts 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.
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