Regeneration of tooth development in vitro following sodium fluoride treatment

Abstract

Mandibular incisors were dissected from the jaw of 15- and 16-day C57BL/10 mouse embryos and cultured on agar-solidified Eagle's basal medium supplemented with fetal calf serum, an antibiotic, and glutamine, The experimental medium was the same as the control except that fluoride was added such that the final concentrations ranged from 2.0-8.0 mM NaF. Control and experimental explants were recovered after two, four and six days of incubation and studied histologically. After two days of fluoride treatment (3.0 mM NaF), cellular degeneration was observed in the dental papilla mesenchyme while the enamel organ epithelium appeared more resistant. Prolonged treatment or treatment at higher concentrations resulted in destruction of the dental papilla. The enamel organ was still present but was abnormal and reduced. Older tooth germs were less affected overal when incubated at the same fluoride dosage and time of treatment. When explants subjected to limited exposure (2 days) to fluoride were placed on control medium, the suppressed tooth germs recovered. The recovery was enhanced by grafting untreated mesenchyme to the treated explants followed by incubation on control medium. The observations indicate that NaF can suppress the development of tooth germs in vitro and that recovery from the suppresion does occur. The more severe inhibition observed in the mesenchymal component when compared to the response of the epithelial component of the treated explants suggests that fluoride may alter the ultimate morphology of the tooth crown by disrupting the normal epithelial-mesenchymal interaction which occurs during early tooth development.

The Effect of Fluoride on the Developing Tooth

“…Almost no effects of fluoride on odontogenic cell differentiation were detected at F50 ÌM peak plasma fluoride concentrations [Walton and Eisenmann, 1974] and up to 265 ÌM in culture medium [Bronckers et al, 1984a], although at higher concentrations (3 mM) a delay in differentiation was reported [Kerley and Kollar, 1977].…”

The Impact of Fluoride on Ameloblasts and the Mechanisms of Enamel Fluorosis

“…There is no evidence that exposure of developing teeth to physiological levels of fluoride, in vivo (Smith et al, 1993) and in organ culture (Kerley and Kollar, 1977;Levenson, 1980;Bronckers et al, 1984a;Bawden et al, 1992), affects tooth morphogenesis, cell proliferation, or differentiation of ameloblasts. Even in highly fluorotic teeth, the size and form of the teeth are not changed (e.g., Kierdorf and Kierdorf, 1997).…”

“…Even in highly fluorotic teeth, the size and form of the teeth are not changed (e.g., Kierdorf and Kierdorf, 1997). In organ culture, proliferating and differentiating pre-ameloblasts are very resistant to fluoride, and fluoride's effects on cell morphology and matrix synthesis have been reported only in the range of 1.3-5.2 mmol F/L (Kerley and Kollar, 1977;Levenson, 1980;Bronckers et al, 1984a;Bronckers and Wöltgens, 1985;Li et al, 2005), which is far higher than the plasma levels that can induce enamel fluorosis in vivo.…”

Effect of Experimental Fluorosis on the Surface Topography of Developing Enamel Crystals

“…Previous investigators have suggested that fluoride affects ameloblast proliferation and differentiation [Kerley and Kollar, 1977;Holland and Hongslo, 1979], ameloblast morphology [Smith et al, 1993], matrix composition and degradation [DenBesten and Crenshaw, 1984;DenBesten and Hefferman, 1990] and matrix-mineral binding [Aoba et al, 1989]. However, many of these results have been equivocal or only present at very high levels of fluoride exposure (notably in the culture fluid for in vitro work) which are not typical of those generally associated with dental fluorosis.…”