title: Evaluation of some properties of an opaque porcelain fired simultaneously with the body porcelain.
abstract: Recently, a porcelain-fused-to-metal opaque porcelain was introduced that does not require a separate firing before application of the body porcelain. The objective of this study was to determine the properties of this new opaque porcelain and its ability to bond to metal. The properties studied included flexural strength, linear firing shrinkage, coefficient of thermal expansion, powder particle size, and ability to bond to body porcelain and dental alloys. Sintering of this opaque porcelain was complete when fired at 1760 degrees F (960 degrees C) with a linear firing shrinkage of 13.1% +/- 0.2%. No boundary between the opaque and body porcelains could be found with a scanning electron microscope after firing at 1760 degrees F (960 degrees C). The mean flexural strengths were 99 +/- 7 and 101 +/- 8 MPa respectively, for this opaque porcelain and a conventional opaque porcelain, and were not significantly different as assessed with Student's t-test (p = 0.548). The coefficients of thermal expansion for this opaque porcelain was 13.3 +/- 0.2 x 10(-6)/degrees C. Particle size analysis showed a 63% increase in the particles below 5 microns for this opaque porcelain and bonding to two alloys was adequate as indicated by its cohesive failure. Simultaneous firing of this special opaque porcelain and body porcelain produced satisfactory sintering, strength, and bonding to metal.
authors.affiliation: Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor.
authors.forename: W J
authors.initials: WJ
authors.lastname: O'Brien
authors.forename: K M
authors.initials: KM
authors.lastname: Boenke
authors.forename: C L
authors.initials: CL
authors.lastname: Groh
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D003735:Dental Casting Technique; D003776:Dental Porcelain / Q000737:chemistry*; D004548:Elasticity; D005069:Evaluation Studies as Topic; D006047:Gold Alloys / Q000737:chemistry; D006358:Hot Temperature; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D003722:Dental Alloys; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; C049241:olympia; C081267:Willceram porcelain