Stress-relieving and porcelain firing cycle influence on marginal fit of commercially pure titanium and titanium–aluminum–vanadium copings

Objectives. This study evaluated: (1) the marginal fit of copings fabricated from commercially pure titanium (cp Ti) and titanium–aluminum–vanadium alloy (Ti–6Al–4V) after each firing cycle for a recommended porcelain; and (2) the effectiveness of a stress-relieving treatment on the fit. The results were compared with copings made with Pd–Ag alloy submitted to the recommended porcelain firing protocol. Methods. Bovine teeth were machined for metal–ceramic crowns and die casts were obtained for waxing patterns. The firing cycle of titanium porcelain was performed on cp Ti and Ti–6Al–4V copings obtained using the Rematitan System. A stress-relieving treatment (cp Ti treated and Ti–6Al–4V treated groups) was performed on original invested castings at the first porcelain firing temperature (800 °C). Fit (μm) was measured in the ‘as cast’ condition and after each porcelain firing cycle with a traveling microscope. The values were compared using the analysis of variance and Tukey's test ( P