Evaluation of glass viscosity of dental bioceramics by the SciGlass information system

The objective of this work was to evaluate the viscosity of glassy dental materials using the SciGlass Information System, testing the hypothesis that there is a common viscosity value at the processing temperature for each manufacturing technique. Ten dental porcelains (seven leucite-based and three totally vitreous), processed by sintering, and one leucite-based-glass–ceramic, processed by the hot-pressing technique, were chemically analyzed by X-ray fluorescence spectroscopy. Specific glasses used in an infiltration process to prepare ceramic composites were analyzed considering eight different compositions reported in literature. The SciGlass program was used to calculate viscosity curves from the chemical compositions. For leucite-based materials, crystalline contents were determined by microstructural analysis. For each material, the viscosity curve as a function of temperature was calculated. The viscosity determined at the processing temperature for different techniques was: 107.0±0.6dPas for sintered dental porcelains; 107.0dPas for hot-pressed leucite-based glass–ceramic; and 102.2±0.3dPas for the glass infiltrated in ceramic preforms. Both chemistry and microstructure affected the viscosity of the materials. The viscosity for hot-pressed leucite-based glass–ceramic was close to the viscosity at Littleton softening point and similar to that of sintered dental porcelains; the viscosity of glasses for infiltration in ceramic preforms was close to the viscosity at their melting point. SciGlass Information System was successful in evaluating the viscosity of glassy dental materials, and can be an useful tool to determine the effect the of the material composition and microstructure on the processing temperature. Also, the viscosity calculated by the software for each manufacturing technique allows for a better compositional design in the development of new materials.