The effects of nicotine on mouse first molar tooth germs in organ culture

Mandibular first molars, extirpated from 18-day mouse fetuses were cultured in BGJb medium (Fitton-Jackson modification) in a Trowell type culture system. Two-day cultures were treated with 78, 117, 156, and 312 microgram/ml nicotine sulfate. Untreated control tooth germs demonstrated normal growth in vitro. The peripheral cell layer of mesenchymal papilla and the inner enamel epithelium differentiated into odontoblasts and ameloblasts respectively with subsequent elaboration of extracellular matrix. Tooth germs treated with 78 microgram/ml nicotine were only slightly affected where as higher doses of the drug produced extensive cell damage. Dental papilla appeared more sensitive than the enamel organ. Large necrotic foci were present in the pulp mesenchyme involving in some cases the odontogenic layer and severely limiting production of predentin. The basement membrane in these areas was partially disrupted and stained poorly for PAS. The inner enamel epithelium was not affected by 78 microgram/ml dose of nicotine, however, higher doses produced extensive cell necrosis in this layer. Although enamel matrix was abundantly present in untreated controls, the tooth germs exposed to 117, 156, and 312 microgram/ml nicotine sulfate failed to elaborate this extracellular matrix. Tooth germs exposed to nicotine for 24 hours followed by culturing in control medium demonstrated complete recovery. Treated cultures maintained in vitro for 7-9 days in control media had replaced the necrotic cells in the ameloblastic and odontoblastic layers and demonstrated abundant dentin and enamel matrices.