Tensile strength of the bond between resin to enamel etched with phosphoric acid containing fluoride

The tensile bond strength of Epoxylite 9075 and Enamelite to enamel treated with NaF and SnF2, at two concentrations, in the etching acid (H3PO4) was determined. The average fracture stress of those samples in which fracture occurred in the resin only, may be considered as the tensile strength of the resin, 69.8 +/- 5.6 kg/cm2. The mean fracture stresses of the Epoxy 9075 systems etched with pure phosphoric acid or with acid solutions containing 0.5% F salts were significantly higher than those treated with acid solutions containing 2% F salts. Incorporation of NaF or SnF2 in the etching solutions highly increased the fluoride concentration of enamel. The fluoride increase dependend on the fluoride concentration of the etching solution and was greater for NaF than SnF2.