title: Evaluation of zirconia-based posterior single crowns supported by zirconia implants: preliminary results of a prospective multicenter study.
abstract: OBJECTIVE
  The aim of this uncontrolled prospective multicenter study was to determine the success and survival rate of posterior single crowns composed of zirconia frameworks hand-layered with a leucite-reinforced feldspathic ceramic supported by one-piece zirconia oral implants.
  
  
  METHODS
  In two centers, sixty patients received 71 zirconia oral implants. To obtain a clear indication of posterior implant-supported single crowns (ISSCs), 14 patients (25 implants) were excluded from the analysis (11 bridges, three anterior crowns). The remaining patients were provided with single implants in posterior regions. As one patient lost his implant and another refused further participation after final prosthesis insertion, 44 ISSCs/patients (19 females, 25 males) were available for evaluation. Of these patients, all were seen at prosthetic delivery and the 6- and 12-month follow-up appointments. Evaluations were performed using modified United States Public Health Service (USPHS) criteria. Restorations within Alpha and Bravo ratings were regarded as success. This included minor chippings, a slight roughness, slightly soundable restoration margins and minimal contour deficiencies. In case of more distinct defects that could, however, be repaired to a clinically acceptable level, restorations were regarded as surviving. Kaplan-Meier plots and log-rank tests were used for the success/survival analyses and the calculation of potential group differences (gender, jaw and center).
  
  
  RESULTS
  After a mean observation period of 12.5 months (SD: 0.8 months), no ISSC had to be replaced, resulting in a Kaplan-Meier survival rate of 100%. The Kaplan-Meier success rate was 90.9% (one major chipping, one obvious roughness, one significant crevice and one pronounced over-contouring). Minor chippings and occlusal roughness were frequent complications. No significantly different survival/success rates could be observed between the mentioned groups.
  
  
  CONCLUSIONS
  The frequent incidence of minor chippings suggests a high technique sensitivity when providing zirconia implants with veneered zirconia-based crowns questioning its suitability for this indication.
authors.affiliation: Department of Prosthetic Dentistry, Center for Dental Medicine, Medical Center - University of Freiburg, Freiburg, Germany.
authors.forename: Benedikt Christopher
authors.initials: BC
authors.lastname: Spies
authors.affiliation: Department of Prosthetic Dentistry, Center for Dental Medicine, Medical Center - University of Freiburg, Freiburg, Germany.
authors.forename: Ralf-Joachim
authors.initials: RJ
authors.lastname: Kohal
authors.affiliation: Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Balmer
authors.affiliation: Center for Medical Biometry and Medical Informatics, Institute for Medical Biometry and Statistics, Medical Center - University of Freiburg, Freiburg, Germany.
authors.forename: Kirstin
authors.initials: K
authors.lastname: Vach
authors.affiliation: Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Jung
mesh_terms: D000328:Adult; D000368:Aged; D002516:Ceramics; D003442:Crowns; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016896:Treatment Outcome; D055815:Young Adult; D015040:Zirconium
chemical_list: D015040:Zirconium; C028541:zirconium oxide
keywords: CAD-CAM; ceramics; crown; dental implant; dental porcelain; fixed bridge; zirconia