[Enamel fluoride uptake following fluoride application and fluoride precipitation]

This study is on fluoride uptake into enamel following fluoride precipitation with calcium hydroxide. Five specimens each from 12 bovine incisors were polished, covered with a salivary pellicle, and distributed into five groups (n=12). A fluoride solution (43,500 ppm F from magnesiumfluorosilicate, copper-(II)-fluorosilicate and sodium-fluoride, pH 2; Tiefenfluorid Touchierlösung, Humanchemie) and Ca(OH)2-solution (Tiefenfluorid Nachtouchierlösung) were applied subsequently in group TN. "Touchierlosung" only was used in group T, sodium-fluoride (43,500 ppm F, pH 2) in group NaF, and aminefluoride (Elmex fluid, 10,000 ppm F, pH 4) in group EF. No fluoride was used in group NK (negative control). Following rinsing and 24 h storage in artificial saliva surface KOH-soluble fluoride content (KOHF), and structurally bound fluoride content (SBF) from three layers (0-33, 33-66 and 66-99 pm) was determined by fluoride electrode procedures. KOHF (median in microg/cm2) of NK was below the lower limit of quantification of the fluoride electrode. The other group values were significantly higher (Mann-Whitney test, p < or = 0.05). TN (1.6), T (1.4) and NaF (1.1) did not differ significantly. EF (0.6) was significantly smaller than TN and T but not smaller than NaF. SBF (0-33, 33-66, 66-99 pm; median in microg/cm3) of TN (445, 341, 275), T (644, 481, 360), NaF (804, 480, 307) and EF (449, 346, 280) did not differ significantly but, with the exception of TN, were significantly higher as compared to NK. A precipitation reaction with Ca(OH)2 following fluoridation did not increase enamel fluoride uptake.