title: Effects of firing cycle and surface finishing on distortion of metal ceramic castings.
abstract: The "as-cast" fit of metal ceramic restorations has been reported to deteriorate during the high-temperature firing cycles used for application of porcelain veneer. In this study, thermocycling and surface finishing or cold working were examined for their effects on marginal adaptation of metal ceramic castings. Methods for minimizing the loss of marginal adaptation were evaluated, and casting variables were eliminated by construction of acrylic resin measuring dies directly in the restorations. Thermocycling of metal ceramic restorations resulted in increased marginal openings, and all of the loss of marginal fit occurred during the first thermocycling of the alloy. The restorations that were cold worked and then oxidized by conventional manipulation had substantially more marginal opening than any other group. A fourfold, statistically significant improvement (p < 0.001) in the marginal adaptation of a metal ceramic restoration was observed when the initial thermal cycle was completed before the specimens were finished.
authors.affiliation: Department of Restorative Dentistry, University of Illinois at Chicago, IL 60612, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Campbell
authors.forename: A
authors.initials: A
authors.lastname: Sirakian
authors.forename: L B
authors.initials: LB
authors.lastname: Pelletier
authors.forename: R A
authors.initials: RA
authors.lastname: Giordano
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003080:Cold Temperature; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique / Q000706:statistics & numerical data; D003737:Dental Cavity Preparation; D003761:Dental Impression Technique; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry; D003801:Dental Veneers; D005069:Evaluation Studies as Topic; D006358:Hot Temperature; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D010084:Oxidation-Reduction; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; D003734:Dental Casting Investment; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain