Combined effect of fluoride and 2,3,7,8-tetrachlorodibenzo-p-dioxin on mouse dental hard tissue formation in vitro.
Fluoride interferes with enamel matrix secretion and mineralization and dentin mineralization. The most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), also impairs dental hard tissue formation and mineralization in vitro and in vivo. Our aim was to investigate in vitro whether the combined effect of sodium fluoride (NaF) and TCDD on dental hard tissue formation is potentiative. For this purpose, mandibular first and second molar tooth germs of E18 mouse embryos were cultured for 5-12 days with NaF and TCDD alone at various concentrations (2.5, 5, 10, 12.5, 15, and 20 μM and 5, 10, 12.5, and 15 nM, respectively) to determine the highest concentrations, which alone cause no or negligible effects. Morphological changes were studied from the whole tooth photographs and histological tissue sections. The concentrations found were 15 μM for NaF and 10 nM for TCDD. While at these concentrations, the effects of NaF and TCDD alone were barely detectable, the effect of simultaneous exposure on dentin and enamel formation was overt; mineralization of predentin to dentin and enamel matrix secretion and mineralization were impaired. Immunohistochemical analysis revealed that the combined exposure modified amelogenin expression by odontoblasts. Morphology of ameloblasts and the expression of amelogenin indicated that ameloblasts were still secretory. The results show that NaF and TCDD have potentiative, harmful effects on the formation of dental hard tissues. Since children can be exposed to subclinical levels of fluoride and dioxins during early childhood, coincidently with mineralization of the first permanent teeth, this finding may have clinical significance.
Department of Pediatric and Preventive Dentistry, Institute of Dentistry, University of Helsinki, 00014 Helsinki, Finland. eija.salmela@helsinki.fi
Eija
E
Salmela
Pirjo-Liisa
PL
Lukinmaa
Anna-Maija
AM
Partanen
Carin
C
Sahlberg
Satu
S
Alaluusua
D053523:Amelogenin / Q000187:drug effects / Q000235:genetics; D000818:Animals; D003743:Dental Enamel / Q000187:drug effects* / Q000378:metabolism; D003804:Dentin / Q000187:drug effects* / Q000378:metabolism; D003810:Dentinogenesis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000008:administration & dosage / Q000633:toxicity; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D051379:Mice; D009804:Odontoblasts / Q000187:drug effects / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000008:administration & dosage / Q000633:toxicity*; D012969:Sodium Fluoride / Q000008:administration & dosage / Q000633:toxicity*
D053523:Amelogenin; D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; D012969:Sodium Fluoride