Resistance to staining, flexural strength, and chemical solubility of coreporcelains for all-ceramic crowns

Purpose: The increased demand for tooth-colored restorations has prompted t he use of ceramics in areas that are subject to masticatory stresses. To ma ximize the strength of these restorations, manufacturers and clinicians adv ocate placement of core materials in lieu of veneering materials in areas t hat are more susceptible to fracture. The objectives of this study were to determine the: resistance to staining of three core porcelains used for all -ceramic restorations, Procera, IFS Empress, and In-Ceram, through the use of colorimetry and visual observation; flexural strength of these porcelain s under a three-point bend test; and chemical solubility in a controlled en vironment. Materials and Methods: L*a*b* values were obtained for each spec imen before and after immersion in a saturated solution of methylene blue i n ethanol for 24 hours. Visual observation was also performed to ascertain color differences before and after staining. A three-point bend test was us ed to determine flexural strength. A reflux-condenser type, three-piece ext raction apparatus was used with 4% acetic acid solution for 16 hours to det ermine solubility. Each sample was weighed before and after the reflux proc edure to ascertain percentage weight loss. Results: The mean DeltaE obtaine d for IFS Empress was 14.5; In-Ceram was 9.2, and Procera was 9.0. Flexural strength obtained for IFS Empress, In-Ceram, and Procera was 176.9 MPa, 32 3.4 MPa, and 464.3 MPa, respectively. Weight loss of IFS Empress, In-Ceram, and Procera was 0.056%, 0.734%, and 0.003%, respectively. Conclusion: IFS Empress showed the least resistance to staining. IFS Empress had the lowest flexural strength, while Procera had the highest. In-Ceram demonstrated th e highest chemical solubility.