title: Randomized clinical trial of implant-supported ceramic-ceramic and metal-ceramic fixed dental prostheses: preliminary results.
abstract: OBJECTIVE
  The aim of this study was to determine the survival rates over time of implant-supported ceramic-ceramic and metal-ceramic prostheses as a function of core-veneer thickness ratio, gingival connector embrasure design, and connector height.
  
  
  METHODS
  An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study involving 55 patients missing three teeth in either one or two posterior areas. These patients (34 women; 21 men; age range 52-75 years) were recruited for the study to receive a three-unit implant-supported fixed dental prosthesis (FDP). Two implants were placed for each of the 72 FDPs in the study. The implants (Osseospeed, Astra Tech), which were made of titanium, were grit blasted. A gold-shaded, custom-milled titanium abutment (Atlantis, Astra Tech), was secured to each implant body. Each of the 72 FDPs in 55 patients were randomly assigned based on one of the following options: (1) A.
  
  
  METHODS
  ceramic-ceramic (Yttria-stabilized zirconia core, pressable fluorapatite glass-ceramic, IPS e.max ZirCAD, and ZirPress, Ivoclar Vivadent) B. metal-ceramic (palladium-based noble alloy, Capricorn, Ivoclar Vivadent, with press-on leucite-reinforced glass-ceramic veneer, IPS InLine POM, Ivoclar Vivadent); (2) occlusal veneer thickness (0.5, 1.0, and 1.5 mm); (3) curvature of gingival embrasure (0.25, 0.5, and 0.75 mm diameter); and (4) connector height (3, 4, and 5 mm). FDPs were fabricated and cemented with dual-cure resin cement (RelyX, Universal Cement, 3M ESPE). Patients were recalled at 6 months, 1 year, and 2 years. FDPs were examined for cracks, fracture, and general surface quality.
  
  
  RESULTS
  Recall exams of 72 prostheses revealed 10 chipping fractures. No fractures occurred within the connector or embrasure areas. Two-sided Fisher's exact tests showed no significant correlation between fractures and type of material system (p = 0.51), veneer thickness (p = 0.75), radius of curvature of gingival embrasure (p = 0.68), and connector height (p = 0.91).
  
  
  CONCLUSIONS
  Although there were no significant associations between connector height, curvature of gingival embrasure, core/veneer thickness ratio, and material system and the survival probability of implant-supported FDPs with zirconia as a core material, the small number of fractures precludes a definitive conclusion on the dominant controlling factor.
authors.affiliation: Department of Restorative Dental Sciences, University of Florida College of Dentistry, Gainesville, FL; Center for Dental Biomaterials, University of Florida College of Dentistry, Gainesville, FL.
authors.forename: Josephine F
authors.initials: JF
authors.lastname: Esquivel-Upshaw
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Clark
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Shuster
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Anusavice
mesh_terms: D000368:Aged; D000538:Aluminum Silicates / Q000737:chemistry; D001031:Apatites / Q000737:chemistry; D002484:Cementation / Q000379:methods; D002516:Ceramics / Q000737:chemistry; D045662:Dental Etching / Q000379:methods; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003801:Dental Veneers; D003779:Denture Design; D003830:Denture, Partial, Fixed; D005260:Female; D005500:Follow-Up Studies; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008297:Male; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008875:Middle Aged; D010165:Palladium / Q000737:chemistry; D010865:Pilot Projects; D019279:Resin Cements / Q000737:chemistry; D016037:Single-Blind Method; D014025:Titanium / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D001031:Apatites; D015921:Dental Implants; D003764:Dental Materials; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; C528569:Rely-X; D019279:Resin Cements; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; C078519:leucite; D015019:Yttrium; D010165:Palladium; C023506:Glass ceramics; D015040:Zirconium; D014025:Titanium; C025105:fluorapatite
keywords: Clinical; design parameters; implants