Titanium is strong, resists corrosion and has a low density and excellent biocompatibility. Conventional ceramic-metal restorations have been extensively used in dentistry because of their esthetic appearance and good mechanical properties. This study investigates oxidation effects on the porcelain-titanium interface reactions and bond strength. Pure titanium was treated in a porcelain furnace at temperatures of 600 to 1000°C under either vacuum or air. X-ray diffraction analysis of the surface of pure titanium revealed that the relative peak intensity of α-Ti decreased and that of TiO₂ increased, with increasing firing temperature. The Vickers hardness number of titanium increased with temperature especially over 900°C, and was harder in air than in vacuum. The tension-shear bond strength of the porcelain-titanium system was the highest in the green stage and lowest after 900°C treatment. Metallographic microscopy of the porcelain-titanium interface revealed a thick band-like zone in the sample treated over 900°C. The excess thick layer of TiO₂ apparently weakened the bond strength of porcelain-titanium. Unlike the conventional ceramic-gold alloy system the recommended degassing procedure was not suitable for porcelain-pure titanium restoration.