Methods: Commercial and in-house prepared ceramic discs were machined and polished (1 μm finish) to various thicknesses, ranging from 0.17 - 2.0 mm. For quantitative translucency values, the differences in luminous reflectance (DE) of the specimens were calculated from the Lab values (CIE) of a white background compared to a black background using a spectrophotometer (SpectroShade micro, MHT S.P.A., VIA MILANO, 12; 37024 ARBIZZANO DI NEGRAR (VR), ITALY).
Results: For 1.0 mm thick specimens, the relative translucencies (DE) of ceramic cores in reference to the transparent soda-lime glass control were 25.41 ± 0.15% (e.max CAD), 23.07 ± 0.19% (e.max Press), 18.91 ± 0.19% (alumina), 16.66 ± 0.53% (Empress II), 7.72 ± 0.27% (GZG), and 6.18 ± 0.21% (zirconia). Various porcelain veneers, however, exhibited transparencies between 43.61% - 51.07% of that of soda-lime glass. For 0.40 mm specimens, e.max Press, e.max CAD, Empress II and alumina possessed a translucency of 42.38%, 38.84%, 30.10% and 26.98% relative to that of 1.0 mm thick glass, while GZG and zirconia displayed a relative translucency of 16.63% and 11.82%, respectively.
Conclusion: Various materials exhibited a wide range of opacity. Specimen thickness also resulted in a large variation in opacity. Our findings suggest that a material’s composition and microstructure, as well as specimen thickness all play an important role in the optical properties of dental ceramics. Supported by NIH/NIDCR-R01DE017925 and NSF/CMMI-0758530.
Keywords: Ceramics and Restorative Materials
See more of: Dental Materials 3: Ceramic-based Materials and Cements