title: Clinical study of the internal gaps of zirconia and metal frameworks for fixed partial dentures.
abstract: The aim of this clinical study was to compare the internal gaps between abutment teeth and posterior fixed partial dentures (FPDs) fabricated utilizing milled zirconia and cast gold-alloy frameworks. As part of an ongoing randomized controlled clinical trial, 32 three-unit FPDs (16 zirconia and 16 metal-ceramic) in 25 patients were randomly selected for adaptation measurements. During the bisque-stage ceramic try-in, an A-silicone impression material was placed between the abutment teeth and the framework. The internal gap, corresponding to the thickness of the replica, was measured under magnification at the following locations: cervical, axial, and occlusal (cusp-tips and central). The internal gaps of FPDs with zirconia frameworks were significantly larger in cervical, axial, and centro-occlusal regions (cervical: 189.6 +/- 71.8 mum vs. 118.6 +/- 31.5 mum; axial: 140.5 +/- 38.3 mum vs. 95.7 +/- 18.1 mum; and centro-occlusal: 192.0 +/- 66.5 mum vs. 153.1 +/- 69.8 mum). The cervical gaps next to the pontics were significantly larger compared with those of the outer walls in both types of FPDs (zirconia: mean difference 67.7 +/- 114.7 mum; metal-ceramic: mean difference 30.0 +/- 71.2 mum). Posterior three-unit FPDs incorporating milled zirconia frameworks exhibited larger internal gaps than those constructed using conventional metal-ceramic techniques.
authors.affiliation: Clinic for Fixed and Removable Prosthodontics and Dental Material Science, Center for Dental and Oral Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Fabian
authors.initials: F
authors.lastname: Wettstein
authors.forename: Irena
authors.initials: I
authors.lastname: Sailer
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Roos
authors.forename: Christoph H F
authors.initials: CH
authors.lastname: Hämmerle
mesh_terms: D017076:Computer-Aided Design; D000044:Dental Abutments; D003735:Dental Casting Technique / Q000295:instrumentation; D003760:Dental Impression Materials; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain; D003779:Denture Design; D003830:Denture, Partial, Fixed; D005260:Female; D006047:Gold Alloys; D006801:Humans; D008297:Male; D016876:Metal Ceramic Alloys; D017755:Prosthesis Fitting; D018709:Statistics, Nonparametric; D019231:Tooth Preparation, Prosthodontic; D015019:Yttrium; D015040:Zirconium
chemical_list: D003760:Dental Impression Materials; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium