EFFECT OF TITANIUM PREOXIDATION ON WROUGHT PURE TITANIUM TO CERAMIC BOND STRENGTH

Statement of problem. The creation of high bond strength between machined computer-manufactured pure titanium and porcelain remains a problem. However, machined titanium does not form the thick titanium oxide film found in cast titanium. Purpose. The purpose of this study was to investigate the effects of different preoxidation treatments on the bond strength of a machined pure titanium ceramic system. Material and methods. Specimens of commercially pure titanium (25 x 3 x 0.5 mm) were divided equally into 6 groups (n=8), which received different preoxidation treatments (3 hour natural oxidation; 600 degrees C, 650 degrees C, 700 degrees C, 750 degrees C, and 800 degrees C for 3 minutes). Bond strengths were evaluated by using a 3-point bend test. The results were analyzed by using 1-way ANOVA and the least significant difference test. Twelve additional specimens of commercially pure titanium (15 x 3 x 0.5 mm) were cut for interface observation and divided equally into 6 groups that received the preoxidation treatments described previously. Scanning electron microscopy and energy dispersive spectrum were used to observe microscopic features of the interface between Ti and ceramic. Results. The bond strength values of the 6 groups ranged from 23.72 +/- 2.53 MPa to 36.99 +/- 3.92 MPa, with significant differences (P<.05). The specimen that received 750 degrees C preoxidation had the highest bond strength. The main interface elements of the 6 groups were O, Si, Ti, Sn, Al, Na, and K. Ti showed a sigmoidal diffusion curve in each group, and Si showed a sigmoidal diffusion curve in most groups. Sn was enriched in each group's interface. Conclusions. Preoxidation under vacuum before porcelain firing can effectively improve the bond strength of machined pure titanium-porcelain systems. (J Prosthet Dent 2013;109:106-112)