Influence of surface oxidation of titanium on adhesion

Objectives: The adhesive bonding of titanium was investigated using a methacrylate-phosphate primer and a luting agent. The present study investigates the influence of heat oxidation as well as a suitable durable bonding method for treating the surface of titanium. Methods: Two groups of disc specimens were fabricated by milling and casting, respectively. Machine-milled specimens were subjected to heat treatment, and three groups of cast metal specimens underwent following respective treatments: (1) as-cast, (2) emery-polishing, (3) alumina-blasting after emery-polishing. The primer contained 10-methacryloyloxydecyl dihydrogen phosphate (MDP); the luting agent was based on methyl methacrylate (MMA), and was initiated with tri-n-butylborane derivative (TBB). Each specimen was primed and bonded to an acrylic rod. Shear bond strengths were determined before and after thermocycling. Results: The mean bond strength of the machine-milled emery-polished group was 32.5 MPa after 5000 thermocycles with only a slight decrease in bond strength. A decrease in the bond strength occurred when the heat-treatment temperature was above 400 °C. Although both emery-polishing and alumina-blasting were effective, the minimum decrease in bond strength was obtained with alumina-blasting. Conclusion: The excess surface oxide layer may be of great concern as a possible cause of decreased bonding durability. Sufficient bonding durability for clinical use was obtained when the titanium was alumina-blasted.