Optical properties and microstructure of dental ceramics

• Grant number: 09/00100-0
• Support Opportunities: Regular Research Grants
• Start date: August 01, 2009
• End date: July 31, 2011
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Paulo Francisco Cesar
• Grantee: Paulo Francisco Cesar
• Host Institution: Faculdade de Odontologia (FO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The objectives of this project are: a) to determine the coefficients of absorption and scattering of 10 dental ceramics by the methods of Kubelka-Munk and Beer-Lambert, and correlate them with the microstructural parameters, and b) verify the applicability of these coefficients to predict the transmitance in the following multilayered systems: EMPRESS (lithium disilicate veneered with fluorapatite-based glassceramic); INCERAM (spinell-glass composite veneered with glassy porcelain); CAD-CAM (tetragonal zirconia polycristal stabilized by itrium veneered with leucite-based porcelain). The following ceramics will be analyzed individually: two porcelains (one vitreous and one leucite-based); three glass-ceramics (one fluorapatite-based, one leucite-based and one with lithium disilicate); three ceramic composites (alumina/glass, alumina-zirconia/glass and spinell/glass); and two polycrystalline ceramics (alumina and tetragonal zirconia stabilized with yttrium). Two resin composites will also be studied: one resin cement and one restorative resin composite. The monolayered specimens will be prepared with thicknesses varying from 2.0 to 0.5 mm. Multilayered specimens will have total thickness of ~4.0 mm (1.0 mm of porcelain, 1.0 mm of core ceramic, a thin layer of resin cement and 2.0 mm of restorative composite. Optical properties will be determined with a spectrophotometer. The reflectance of specimens will be measured over two background colors (black and white) in order to determine the contrast ratio (CR). Direct and Total transmittance spectra will also be measured. The coefficient of apparent absorption, k, from the Beer-Lambert equation will be determined from the transmittance values obtained in the different thicknesses. The coefficients of scattering, S, and absorption, K, from the Kubelka-Munk model will be obtained from the reflectance results in the different backgrounds (black and white). The reflectance and transmittance spectra of the multilayered specimens will be measured before and after cementation. These results will be compared to the theoretical spectral curve predicted from the coefficients of absorption and scattering determined for each of the layers individually. Microstructural characterization will be performed by means of scanning electron microscopy and an image analyzer. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

DE ARAUJO, MAICO DUTRA; DE PAULA MIRANDA, RANULFO BENEDITO; FREDERICCI, CATIA; YOSHIMURA, HUMBERTO NAOYUKI; CESAR, PAULO FRANCISCO. Effect of fiber addition on slow crack growth of a dental porcelain. JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS, v. 44, p. 85-95, APR 2015. (09/00100-0)