Manufacture of Paste Opaque Porcelains Using Glycols as a Solvent and Evaluation of their Physical Properties

Paste opaque porcelains are used in metal-ceramic systems in order to laminate opaque porcelains in thin layers, interrupt the metal color effectively, and enhance workability. We manufactured the paste opaque porcelains using Propylene Glycol (PG) and Butylene Glycol (BG) as a solvent, and compared viscosity, the coefficient of thermal expansion, debonding/crack-initiation strength to metal, SEM observations of the interface between porcelain and metal, and color with those of the commercial products (Duceram Plus, Duceram GmbH; VMK 95, Vita Co.; Noritake EX-3, Noritake Co.) used in the clinical field. The viscosity of test materials was measured using viscometer at 25°C. The coefficient of thermal expansion and debonding/crack-initiation strength to metal were measured by ISO 9693:1999, and the color was evaluated by a CIELab system. The rheological property of tested materials showed pseudo-plastic behavior. The coefficient of thermal expansion (×10^-6K^-1) of the tested material ranged from 13.3 to 14.3 while debonding/crack-initiation strength (MPa) ranged from 35 to 41. ISO requires debonding/crack-initiation to be over 25 MPa. All test groups adhere effectively onto the metal surface in the SEM observations. And the colors of tested materials were distinguishable from each other despite of having similar shades (A3).