Effect of hydrolyzed surface layer on the cytotoxicity and chemical resistance of a low fusing porcelain

Objectives. The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC and to determine its effect on the cytotoxicity of the porcelain as measured by cellular activity and concentrations of leached ionic species. Methods. Specimens were fabricated from dentin porcelain by a vibration blotting technique. Half of the specimens underwent accelerated aging by subjecting them to the standard test for hydrolytic resistance (ISO 6872). Fibroblast cell cultures were placed in direct contact with specimens. Cell viability was assessed using succinic dehydrogenase activity. Chemical resistance was determined by leaching specimens with a continuous flow of deionized water and measuring the concentrations of soluble ions in the leachates. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to detect the composition of the surface layer. Results. Hydrolyzation treatment created a smooth texture on the porcelain surfaces but did not result in a hydrolyzed surface layer with increased hydroxyl content. There was a decreased alkali ion content in the surface layer of hydrolyzed specimens. Mean cellular SDH activities for non-hydrolyzed and hydrolyzed porcelain were 75±7 and 80±5% of Teflon® controls, respectively. Only sodium ions were present in significant concentrations in collected leachates. The sodium concentration decreased over the initial 4.5 h of leaching. Significance. The changes in surface layer texture and composition as the result of the aging treatment had little effect on the cytotoxicity and chemical resistance of Duceram LFC. The results suggest that Duceram LFC would pose no biocompatibility risk even after extended exposure to the oral environment. These data also provide baseline material properties to be used in future studies of the effects of porcelain additives.