title: Clinical efficacy of veneered zirconium dioxide-based posterior partial fixed dental prostheses: five-year results.
abstract: BACKGROUND
  In recent years, zirconium dioxide-based partial fixed dental prostheses (FDP) have been suggested as an alternative treatment to traditional metal ceramic FDPs. However, clinical studies evaluating their longevity and related complications are limited.
  
  
  OBJECTIVE
  The purpose of this cohort clinical study was to assess the efficacy of zirconium dioxide-based posterior 3-unit FDPs.
  
  
  METHODS
  Twenty 3-unit posterior FDPs (Lava) were placed in 16 participants missing a second premolar or a first molar. All participants met specific inclusion and exclusion criteria and provided informed consent. All teeth were prepared in a standardized manner: occlusal reduction of 1.5 to 2 mm; axial reduction of 1 to 1.5 mm; a 1.0 mm 360-degree rounded shoulder placed 0.5 mm subgingivally on the facial aspect and supragingivally on the lingual aspect on sound tooth structure; and rounded internal line angles. Definitive impressions were made with vinyl polysiloxane impression material. Frameworks were fabricated by using computer-aided design and computer-aided manufacturing (CAD/CAM) technology with a uniform retainer thickness of 0.6 mm and a minimal connector surface area of 9 mm(2). Restorations were luted with resin-modified glass ionomer cement (Rely-X Luting). Participants were recalled at 2 weeks, 6 months, and 12 months, and thereafter, annually for up to 60 months. Clinical fracture measurements, marginal discoloration, marginal adaptation, radiographic proximal recurrent caries, and periapical pathoses were assessed over time by using modified Ryge criteria. The probability distributions of these variables were calculated for the baseline data and for the recall data. An analysis of survival was made by using the Kaplan-Meier method.
  
  
  RESULTS
  Eighteen FDPs were clinically evaluated at 5 years and 1 at 48 months. Fifteen were rated Alpha for fracture measurements, and 2 were rated Bravo (minor chipping of veneering porcelain and not requiring restoration replacement). Two were rated Charlie (major chipping of veneering porcelain and requiring restoration replacement). Eighteen FDPs were rated Alpha for marginal integrity, and 1 rated Bravo. All restorations were rated Alpha for marginal discoloration. One participant experienced root fracture after 60 months, while another was treated surgically for a periapical pathosis on an endodontically treated abutment.
  
  
  CONCLUSIONS
  Zirconium dioxide-based posterior 3-unit FDPs performed well after 5 years of service.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, WA 98195-7456, USA. araigrod@u.washington.edu
authors.forename: Ariel J
authors.initials: AJ
authors.lastname: Raigrodski
authors.forename: Alika
authors.initials: A
authors.lastname: Yu
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Chiche
authors.forename: J L
authors.initials: JL
authors.lastname: Hochstedler
authors.forename: Lloyd A
authors.initials: LA
authors.lastname: Mancl
authors.forename: Shawky E
authors.initials: SE
authors.lastname: Mohamed
mesh_terms: D000328:Adult; D001641:Bicuspid; D015331:Cohort Studies; D003116:Color; D003188:Composite Resins / Q000737:chemistry; D017076:Computer-Aided Design; D003731:Dental Caries / Q000000981:diagnostic imaging; D003761:Dental Impression Technique; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D019232:Dental Restoration Failure; D003801:Dental Veneers; D003779:Denture Design; D003830:Denture, Partial, Fixed; D005260:Female; D005500:Follow-Up Studies; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D008963:Molar; D010483:Periapical Diseases / Q000000981:diagnostic imaging; D011859:Radiography; D019279:Resin Cements / Q000737:chemistry; D016019:Survival Analysis; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D016896:Treatment Outcome; D015040:Zirconium / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D005899:Glass Ionomer Cements; D019279:Resin Cements; C084550:Vitremer; D015040:Zirconium; C028541:zirconium oxide