Fluoride and magnesium content in superficial enamel layers of teeth with erosions

In the absence of any previous research on the content of fluoride and magnesium in superficial enamel layers of eroded teeth in relation to acid resistance of the enamel, a study was undertaken to determine the concentration of both elements in eroded teeth using the acid biopsy technique. Biopsies were obtained from the labial surface below (upper dentition) or above (lower dentition) the erosion from the following teeth: one upper central incisor, five upper canines, three lower canines, two upper premolars, and three lower premolars. Corresponding teeth without erosions from age- and gender-matched patients living in the same area served as controls. Microsamples of enamel were obtained using 3 mu L of 0.5 M perchloric acid. Fluoride concentrations were measured chromatographically, and magnesium and calcium were determined by atomic absorption spectrometry. Teeth with enamel erosions had significantly lower concentrations of both fluoride and magnesium as well as lower resistance to penetration by acid. Significantly lower concentrations of fluoride and magnesium were found in upper as well as in deeper enamel layers of eroded teeth compared to controls. These findings confirm an association between the content of fluoride and magnesium and acid resistance in dental enamel, which is reduced in teeth with erosions. In areas of low exposure to fluoride, topical fluoride may be protective against enamel erosion by acids, especially in carbonated beverages.