The effect of fluoride in phosphoric acid on enamel fluoride uptake and the tensile bond strength of an orthodontic bonding resin

Abstract

Decalcification that occurs adjacent to bonded orthodontic brackets is of great concern to orthodontists. Among the many procedures suggested to overcome this problem is the addition of fluoride to the phosphoric acid (H 3PO 4,) etching solution. The purposes of this study were to determine the loss of fluoride from the acidic etching solutions, to evaluate the effect of various fluoride concentrations in H 3PO 4, on the tensile bond strength of an orthodontic bonding resin, to determine the amount of total and bound fluoride acquired by etched enamel, and to evaluate the effect of these etching solutions on enamel by scanning electron microscopy. Solutions of 50 m/m% H 3PO 4 containing 0 and approximately 0.01, 0.04, 0.08, 0.2, 0.4 and 0.9% fluoride were prepared. The fluoride concentrations in the etching solutions remained stable up to 3 months after preparation. The tensile bond strengths of the bonding resin to the etched enamel surfaces were not significantly different. Enamel acquired the greatest amount of total fluoride from H 3PO 4 solutions containing 0.215% fluoride while the bound fluoride acquired by enamel from the fluoride-containing etching solutions was not significantly different. The addition of fluoride to H 3PO 4 did not impede the etching effect on enamel.