title: Ultrastructure of in-vitro recovery of mineralization capacity of fluorotic enamel matrix in hamster tooth germs pre-exposed to fluoride in organ culture during the secretory phase of amelogenesis.
abstract: The recovery of mineralization capacity of fluorotic enamel matrix was investigated in 3-day-old hamster first molar tooth germs already pre-exposed in organ culture to 10 parts/10(6) F- for 24 h during the secretory phase. The germs were then cultured for another 24 h in a fresh medium without F-. The unmineralized fluorotic enamel matrix secreted in vitro eventually mineralized in the absence of F- but the orientation of the crystals compared to those in the fluorotic enamel was disturbed, especially in the younger regions of the enamel nearest cervical-loop in which the underlaying fluorotic enamel was most hypermineralized; but least disturbed in the more mature parts of the enamel organ in which the fluorotic enamel was less hypermineralized. The subsequent culture in F(-)-free medium did not abolish or reduce the degree of hypermineralization induced by F- treatment during the initial 24 h of culture. It seems that in vitro the inhibitory effect of F- on enamel matrix mineralization during the secretory phase is completely reversible when the ion is removed from the matrix environment, i.e. F(-)-induced synthesis and secretion of defective enamel matrix is not the cause of the lack of matrix mineralization. The F(-)-induced hypermineralization seems to be irreversible.
mesh_terms: D000566:Amelogenesis / Q000187:drug effects*; D000818:Animals; D006224:Cricetinae; D003743:Dental Enamel / Q000187:drug effects / Q000648:ultrastructure*; D005459:Fluorides / Q000494:pharmacology*; D009050:Fluorosis, Dental / Q000473:pathology; D008647:Mesocricetus; D008854:Microscopy, Electron; D009924:Organ Culture Techniques; D014074:Tooth Calcification / Q000187:drug effects*; D014083:Tooth Germ / Q000187:drug effects / Q000648:ultrastructure*
chemical_list: D005459:Fluorides