Combined effect of amoxicillin and sodium fluoride on the structure of developing mouse enamel in vitro

Excess fluoride intake during tooth development is known to cause dental fluorosis. It has also been suggested that amoxicillin use in early childhood is associated with enamel hypomineralization. The aim was to investigate separate and combined effects of sodium fluoride (NaF) and amoxicillin on enamel formation in vitro.

Mandibular molar tooth germs of E18 mouse embryos were cultured for 10 days in a medium containing NaF (10, 12 or 15μM) and/or amoxicillin (0.5, 1, 2 or 3.6mg/mL) or sodium clavulanate (0.07mg/mL) alone or in combination with 0.5mg/mL of amoxicillin. Morphological changes were studied from the whole tooth photographs and histological tissue sections with light microscope.

Only with the highest concentrations of NaF or amoxicillin alone the extent of enamel in the first molars measured as the vertical enamel height/crown height ratio was reduced (p<0.01, p<0.001, respectively). At lower concentrations, combination of NaF (12μM) and amoxicillin (2mg/mL) significantly reduced enamel extent compared with the controls (p<0.001). Histologically, the ameloblasts were still columnar but poorly organized and the nascent enamel was often non-homogeneous. Enamel formation was not seen in any second molars exposed to 12μM NaF and 2mg/mL of amoxicillin (or higher concentrations) compared with the presence of enamel in half of the controls (p<0.001).

Amoxicillin and NaF dose dependently affect developing enamel of mouse molars in vitro and the effects are potentiative. The clinical significance of the results remains to be studied.