title: In vitro precision of fit of computer-aided designed and computer-aided manufactured titanium screw-retained fixed dental prostheses before and after ceramic veneering.
abstract: OBJECTIVE
  To compare the precision of fit of full-arch implant-supported screw-retained computer-aided designed and computer-aided manufactured (CAD/CAM) titanium-fixed dental prostheses (FDP) before and after veneering. The null-hypothesis was that there is no difference in vertical microgap values between pure titanium frameworks and FDPs after porcelain firing.
  
  
  METHODS
  Five CAD/CAM titanium grade IV frameworks for a screw-retained 10-unit implant-supported reconstruction on six implants (FDI tooth positions 15, 13, 11, 21, 23, 25) were fabricated after digitizing the implant platforms and the cuspid-supporting framework resin pattern with a laser scanner (CARES(®) Scan CS2; Institut Straumann AG, Basel, Switzerland). A bonder, an opaquer, three layers of porcelain, and one layer of glaze were applied (Vita Titankeramik) and fired according to the manufacturer's preheating and fire cycle instructions at 400-800 °C. The one-screw test (implant 25 screw-retained) was applied before and after veneering of the FDPs to assess the vertical microgap between implant and framework platform with a scanning electron microscope. The mean microgap was calculated from interproximal and buccal values. Statistical comparison was performed with non-parametric tests.
  
  
  RESULTS
  All vertical microgaps were clinically acceptable with values <90 μm. No statistically significant pairwise difference (P = 0.98) was observed between the relative effects of vertical microgap of unveneered (median 19 μm; 95% CI 13-35 μm) and veneered FDPs (20 μm; 13-31 μm), providing support for the null-hypothesis. Analysis within the groups showed significantly different values between the five implants of the FDPs before (P = 0.044) and after veneering (P = 0.020), while a monotonous trend of increasing values from implant 23 (closest position to screw-retained implant 25) to 15 (most distant implant) could not be observed (P = 0.169, P = 0.270).
  
  
  CONCLUSIONS
  Full-arch CAD/CAM titanium screw-retained frameworks have a high accuracy. Porcelain firing procedure had no impact on the precision of fit of the final FDPs. All implant microgap measurements of each FDP showed clinically acceptable vertical misfit values before and after veneering. Thus, the results do not only show accurate performance of the milling and firing but show also a reproducible scanning and designing process.
authors.affiliation: Department of Prosthodontics, School of Dental Medicine, University of Bern, Bern, Switzerland; Department of Preventive and Restorative Sciences, Robert Schattner Center, University of Pennsylvania School of Dental Medicine, Philadelphia, PA, USA.
authors.forename: Joannis
authors.initials: J
authors.lastname: Katsoulis
authors.forename: Regina
authors.initials: R
authors.lastname: Mericske-Stern
authors.forename: Norbert
authors.initials: N
authors.lastname: Enkling
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Katsoulis
authors.forename: Markus B
authors.initials: MB
authors.lastname: Blatz
mesh_terms: D001863:Bone Screws; D002516:Ceramics; D017076:Computer-Aided Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003801:Dental Veneers; D003779:Denture Design; D003834:Denture Precision Attachment; D003830:Denture, Partial, Fixed; D066298:In Vitro Techniques; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D014025:Titanium
chemical_list: D014025:Titanium
keywords: computer-aided designed and computer-aided manufactured; fixed dental prosthesis; implant framework fit; implant-supported; passive fit; porcelain firing; precision of fit