Surface modification of feldspar porcelain by corona discharge and its effect on bonding to resin cement with silane...

This study aims to develop a corona discharge process for a surface treating a glass-ceramic, feldspar porcelain, to improve its bonding to a resin cement with a silane-coupling agent. Corona discharge, a type of plasma process, was performed using a custom-made device on a porcelain surface at temperatures ranging from 25 to 300 °C, for specific treatment times in air. The porcelain was then subjected to a post-heat-treatment at 600 °C to condition the surface state. The resulting surface was primed with a silane-coupling-agent followed by cementing using a resin cement to measure the shear bond strength (SBS). To investigate the effect of surface modifications by the corona discharge treatment, the porcelain was characterized by surface roughness, contact angle, and an X-ray photoelectron spectroscopy analyses. The SBS for the corona-discharge-treated porcelain increased with an increase in treatment-temperature and -time, and reached the maximum value at 200 °C and 5 min. The post-heat-treatment improved the bond durability after thermocycling. The SBS for the corona-discharge-treated porcelain was then compared to that of a conventional hydrofluoric-acid-treated one, which showed that the SBSs were comparable. The results of the surface characterizations indicated that the corona discharge treatment generated silanol groups on the porcelain surface giving hydrophilic properties without roughening the surface. It was found that the corona discharge treatment generates silanol groups on the porcelain surface, resulting in an increased SBS. This study is the first to demonstrate that corona discharge treatment is effective for improving bond strength through the modification of the surface of glass-ceramics.