title: An esthetic glass-ceramic for use in composite restoration inserts.
abstract: The objective of the preliminary work reported here was to prepare an improved formulation of intrinsically colored microcrystalline glass-ceramic. Applications could include "megafillers" for direct composite restorations, precision castings, and CAD-CAM prostheses. The experimental glass-ceramic reported here contained SiO2 56.9, AI2O3 19, LiO2 7, ZnO 6, MgO 5, TiO22, ZrO22, P2O52, and CeO20.1 mole%. The batch materials were melted and stirred at 1,610 degrees C for 2 h, quenched in water and also formed into a block of a clear, slightly yellow glass. To identify the crystalline phases that developed during transformation of the glass to the ceramic, x-ray diffraction was used on ten aliquots taken during 15 h of stepwise heating from 750 to 1050 degrees C. With heating, the yellow color deepened to a very translucent "dark yellow" dental shade, then lightened with gradually increasing opacity during formation of secondary crystalline phases. X-ray opacity was approximately equivalent to that of dental enamel. The refractive index of the glass, nD1.554, increased during nucleation and growth of the crystalline phases to a maximum of 1.586. Intrinsic coloration of these glass-ceramic materials can be controlled by varying the heat treatment and/or composition to match typical dental shades.
authors.affiliation: Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, MD.
authors.forename: R L
authors.initials: RL
authors.lastname: Bowen
authors.forename: L A
authors.initials: LA
authors.lastname: George
authors.forename: F C
authors.initials: FC
authors.lastname: Eichmiller
authors.forename: D N
authors.initials: DN
authors.lastname: Misra
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D003116:Color; D003188:Composite Resins; D003776:Dental Porcelain / Q000737:chemistry*; D003793:Dental Restoration, Permanent; D004055:Differential Thermal Analysis; D004548:Elasticity; D005898:Glass / Q000737:chemistry*; D006244:Hardness; D006358:Hot Temperature; D011791:Quartz / Q000737:chemistry*; D012031:Refractometry; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: C088834:Beta-Quartz glass-ceramic; D003188:Composite Resins; D003776:Dental Porcelain; D011791:Quartz