Effects of a fluoride etchant on resin bonding to titanium-aluminum-niobium alloy

This investigation was carried out in order to evaluate ammonium hydrogen fluoride (AHF) and cupric chloride (CC) as components of a metal etchant. The surface of cast titanium-aluminum-niobium (Ti-6Al-7Nb) was air-abraded with alumina, etched for 10 s, and rinsed with water. A phosphate or a thiophosphate primer was applied to the bonding area, and an acrylic rod was bonded to the specimen with a tri-n-butylborane-initiated self-curing luting agent. Shear bond strengths were determined after thermocycling (4 degrees C and 60 degrees C) for 10,000 cycles. The average bond strength was significantly influenced by thermocycling, AHF, and primer, but was not influenced by CC. The maximum average bond strengths were obtained when the etchant consisted of 5mass% AHF, with and without 0.3mass% CC. Microphotographs showed that numerous micropits were created on the etched surface, suggesting increased micromechanical retention. In conclusion, chemical etching with 5mass% AHF significantly improved the durability of resin bonding to Ti-6Al-7Nb.