Shear bond strengths of polymethyl methacrylate to cast titanium and cobalt-chromium frameworks using five metal primers.

STATEMENT OF PROBLEM Poor chemical bonding of a denture base resin to cast titanium frameworks often introduces adhesive failure and increases microleakage. PURPOSE This study examined the shear bond strengths of a denture base resin to cast pure titanium, Ti-6Al-4V, and a cobalt-chromium alloy using various adhesive primers. MATERIAL AND METHODS Disks (6.0 mm diameter, 2.5 mm thick) were cast of the 3 alloys. The disk surfaces were grit-blasted with 50 microm alumina and treated with 5 different metal primers (Metal Primer II ¿MP]; Cesead Opaque primer ¿OP]; Meta Base ¿MB]; experimental primer ¿EP]; Siloc bonding system ¿SI]). A denture base resin (Palapress Vario) was then applied on the disks with hole-punched sticky tape (bonding area of 5.0 mm) and a Teflon (PTFE, New Age Industries Inc, Willow Grove, Pa.) ring (6.0 mm diameter x 2.0 mm thick). Specimens without primer were also prepared as controls. All specimens were immersed in 37 degrees C water and thermocycled up to 2,000 cycles. Shear bond strength values were determined at a crosshead speed of 0.5 mm/min. Data were statistically analyzed using 3-way ANOVA, followed by 1-way ANOVA and the Scheffé multiple range test. RESULTS Primers significantly (P <.05) improved shear bond strengths of denture base resin to all metals, among which no significant differences were found. Specimens primed with OP, MP, and EP showed higher bond strengths than did those primed with MB. After thermocycling, the bond strengths of MB and SI decreased substantially; MB showed the least durability (22.8% to 35.5% decrease) among the primers. CONCLUSION The application of 5 primers significantly improved the shear bond strengths of a denture base resin to cast CP titanium, Ti-6Al-4V, and Co-Cr alloy. OP and MP primers exhibited greater bond strength and durability than did MB and SI.