EFFECT OF FLUORIDE COMPLEX FORMATION ON FLUORIDE UPTAKE AND RETENTION IN HUMAN ENAMEL

In vitro treatment and washing procedures were used to study the effect of various metals (Al, Ti, Zr, La, Fe, Be, Sn, Mg, Zn) on the uptake and retention of fluoride from APF solution (0.1 M H3PO4 1.2 per cent F, pH 3.2) on intact blocks of enamel. Aluminium, which was studied most extensively, was applied before, during or after the APF treatment and either as an Al salt or as an Al-F complex. Maximum retention was obtained when enamel was first treated with a solution of an Al salt, followed by application of the APF solution. In general, enhanced F uptake could be obtained with any polyvalent metal capable of forming strong fluoride complexes while simultaneously binding firmly to the enamel apatite crystals. Divalent metals, including strong F complexers such as Be or Sn, were ineffective as they could not perform both functions at the same time. Enamel treated for 1 min with 0.05M Al(NO3)3, then 3 min with APF, and washed 40 hr at pH 5.5 in acetate buffer containing 1 mM Ca and 5 mM P retained about 1800 ppm F in the outer 25 μ compared to 800 ppm F in the outer 25 μ from APF only. Teeth extracted 1 week after a similar treatment in vivo showed an even greater F uptake and penetration (3700 ppm in the outer 50 μ compared to 500 ppm from APF only). Titanium increased F retention more than aluminium. In vivo enamel biopsy studies showed that F retention was undiminished 6-12 weeks after treatment using Al or Ti. © 1969.