Flexural strength of feldspathic porcelain treated with ion exchange, overglaze, and polishing.

Feldspathic porcelains, which are used in the construction of porcelain-fused-to-metal (PFM) restorations, have an inherent weakness because of their brittle nature and processing flaws. A relatively new product, the Tuf-Coat ion exchange system, claims to substantially strengthen feldspathic porcelains. This study compared the strengthening effect of the Tuf-Coat system with that of surface treatments such as overglazing, polishing, and finishing. Bend bars of Vita VMK 68 porcelain were made and randomly assigned to eight different surface treatment groups to examine these effects. The flexural strengths revealed that although Tuf-Coat treatment strengthened the porcelain, it was not significantly different from overglazing, and the strengthening effect was lost if the porcelain was subsequently self-glazed or finished.