title: A randomized controlled clinical trial of 3-unit posterior zirconia-ceramic fixed dental prostheses (FDP) with layered or pressed veneering ceramics: 3-year results.
abstract: OBJECTIVE
  The aim of the present pilot study was to test whether or not posterior zirconia-ceramic fixed dental prostheses (FDPs) with pressed veneering ceramic exhibit less chipping than FDPs with layered veneering ceramics.
  
  
  METHODS
  Forty patients (13 female, 27 male; mean age 54 years (range 26.1-80.7 years) in need of one maxillary or mandibular three-unit FDP in the second premolar or molar region were recruited and treated at two separate centers at the University of Zurich according to the same study protocol. The frameworks were made out of zirconia using a CAD/CAM system (Cerec Sirona, Bensheim, Germany). The patients were randomly assigned to either the test group (zirconia frameworks veneered with pressed ceramic; IPS e.max ZirPress, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20) or the control group (layered veneering ceramic; IPS e.max Ceram, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20). All FDPs were adhesively cemented and evaluated at baseline (i.e., cementation), at 6 months and at 1 and 3 years of clinical service. The survival of the reconstruction was recorded. The technical outcome was assessed using modified United States Public Health Services (USPHS) criteria. The biologic parameters analyzed at abutment teeth and analogous non-restored teeth included probing pocket depth (PPD), plaque control record (PCR), bleeding on probing (BOP), and tooth vitality (CO2). Data was descriptively analyzed and survival was calculated using Kaplan-Meier statistics.
  
  
  RESULTS
  36 patients (25 female, 11 male; mean age 52.3 years) with 18 test and 18 control FDPs were examined after a mean follow-up of 36 months (95% CI: 32.6-39.1 months). Comparison of groups was done by Crosstabulation showing even distribution of the respective restored teeth amidst the groups. Survival rate was 100% for both test and control FDPs. Chipping of the veneering ceramic tended to occur more frequently in test (n=8; 40%) than in control (n=4; 20%) FDPs, albeit not significantly (p=0.3). No further differences of the technical outcomes of test and control FDPs occurred.In both test and control group healthy conditions and no difference of the biologic parameters at the abutment and un-restored teeth was found.
  
  
  CONCLUSIONS
  Zirconia FDPs with pressed and layered veneering ceramics exhibited similar outcomes at 3 years. A trend to more chipping of the pressed veneering ceramic, however, was observed.
  
  
  CONCLUSIONS
  Posterior restorations with zirconia frameworks are a viable treatment method. When restoring posterior teeth with all-ceramic restorations, care providers should be aware of the higher rate of chipping compared to the published data on conventional metal-ceramic restorations.
authors.affiliation: Clinic for Fixed and Removable Prosthodontics and Dental Material Science, University of Zurich, Zurich, Switzerland. Electronic address: nadja.naenni@zzm.uzh.ch.
authors.forename: Nadja
authors.initials: N
authors.lastname: Naenni
authors.affiliation: Clinic of Preventive Dentistry, Periodontology and Cariology, University of Zurich and Private Practice, Zurich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bindl
authors.affiliation: Private Practice, Horgen, Switzerland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Sax
authors.affiliation: Clinic of Fixed and Removable Prosthodonticsa and Dental Material Science, University of Zurich, Zurich, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Hämmerle
authors.affiliation: Division of Fixed Prosthodontics and Biomaterials, University of Geneva, Geneva, Switzerland.
authors.forename: Irena
authors.initials: I
authors.lastname: Sailer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002516:Ceramics / Q000627:therapeutic use*; D003776:Dental Porcelain / Q000627:therapeutic use*; D003801:Dental Veneers / Q000009:adverse effects / Q000706:statistics & numerical data; D003830:Denture, Partial, Fixed / Q000009:adverse effects / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D015040:Zirconium / Q000627:therapeutic use*
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Ceramics; Fixed-dental prostheses; Pressed ceramic; Zirconia