Strong and Weak Acid Sampling for Fluoride of Enamel Remineralized in Sodium Fluoride Solutions

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Abstract
Enamel surfaces were immersed for 24 h in pH 7.0 mineralizing solutions containing 1.5 mM Ca, 0.9 mM inorganic phosphate, and 0.00, 0.05, 0.50 or 5.0 mM NaF. Changes of calcium, phosphate and fluoride concentrations and pH titrations were monitored to assess attainment of steady state between the solution and solid phases. No changes occured in NaF-free solutions during enamel immersion. The results indicated deposition of an F-containing apatite on surfaces immersed in 0.5 mM NaF solutions in larger amounts than in 0.05 or 5.0 mM NaF solutions. However, greater F deposition occurred on surfaces exposed to 5.0 mM NaF solutions, Less Ca and PO4 (PO4 = H2PO––4, HPO4––2, and PO4––3) dissolved in HClO4from 0.5 and 5.0 mM NaF-treated than from control surfaces. Similarly, less PO4 dissolved from 0.5 and 5.0 mM NaF-treated than from 0.05 mM NaF-treated surfaces in an acetate buffer of pH 4.0. Fluoride concentrations greater than 0.05 mM F–– would tend to form CaF2 deposits on the tooth surface, while concentrations less than 0.5 mM F–– would tend to accelerate remineralization by forming mostly fluorapatite. We concluded that frequent applications of F levels of 0.26–0.50 mM may provide safe and optimal resistance to caries.