Evaluation of Bond Strength of Pressed and Layered Veneering Ceramics to Nickel-Chromium Alloy

Statement of the Problem: The success of metal- ceramic- restorations (MCR) depends on the presence of strong bond between porcelain and metal substructure. The purpose of this study was to evaluate the effect of hot pressing technique on the bond strength of a metal-porcelain composite in comparison to layering technique. Thirty Nickel-Chromium specimens were produced by two methods; conventional porcelain layering on metal and hot pressing (n=15). Bond strengths of all specimens were assessed by the means of three–point bending test according to ISO 9693: 1999 (E) instructions. The data were analyzed using Students t-test (p< 0.001). The mean ± SD bond strength of conventional and hot pressing technique was 48.29 ± 6.02 and 56.52 ± 4.97, respectively. Therefore, the conventional layering technique yielded significantly lower mean bond strength values than hot pressing technique (p< 0.001). This study showed that it is possible to improve metal–porcelain bond strength significantly by applying an overpressure during porcelain firing.