title: Marginal adaptation of three different zirconium dioxide three-unit fixed dental prostheses.
abstract: BACKGROUND
  Marginal adaptation is important for the long-term success of dental restorations. Data on the marginal discrepancy of zirconia-based fixed dental prostheses made with different computer-aided design/computer-aided manufacturing technology is needed.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the marginal adaptation of different zirconia 3-unit fixed dental prostheses at different fabrication stages and after artificial aging.
  
  
  METHODS
  Twenty-four zirconia 3-unit fixed dental prostheses (DCS, Procera, and VITA YZ-Cerec; n=8) were fabricated using different manufacturing systems and conventionally cemented with glass ionomer cement on human teeth. Each group was aged in a masticatory simulator with thermal cycling. The marginal gaps were examined on epoxy replicas for frameworks and for restorations before and after cementation, and after masticatory simulation, at x 250 magnification. Marginal adaptation was assessed using geometric means of the marginal gap values with 95% confidence intervals. Differences between the manufacturing systems and the effect of artificial aging were tested using repeated-measures ANOVA and post hoc paired and unpaired t tests with Bonferroni-Holm correction (alpha=.05).
  
  
  RESULTS
  The geometric mean (95% confidence limits) marginal gap values (mum) for frameworks and for restorations before cementation, after cementation, and after masticatory simulation were, respectively: DCS: 86 (80-93), 86 (83-90), 86 (78-94), and 84 (79-90); Procera: 82 (74-89), 89 (81-97), 89 (84-95), and 88 (82-94); and VITA YZ-Cerec: 64 (57-72), 67 (61-77), 76 (71-82), and 78 (76-80). The repeated-measures ANOVA showed significant group and stage effects (P<.05). Group VITA YZ-Cerec showed significantly smaller marginal gap values than groups DCS and Procera at framework (P<.05) and before-cementation (P<.05) stages. The VITA YZ-Cerec group showed significantly smaller marginal gap values than the Procera group after cementation (P<.05). The marginal gap values between different stages were not significantly different for all groups (P>.05).
  
  
  CONCLUSIONS
  The marginal accuracy of zirconia fixed dental prostheses is influenced by manufacturing technique.
authors.affiliation: Department of Prosthodontics, School of Dentistry, Albert-Ludwigs University, Freiburg, Germany. wael.att@uniklinik-freiburg.de
authors.forename: Wael
authors.initials: W
authors.lastname: Att
authors.forename: Futoshi
authors.initials: F
authors.lastname: Komine
authors.forename: Thomas
authors.initials: T
authors.lastname: Gerds
authors.forename: Jörg Rudolf
authors.initials: JR
authors.lastname: Strub