title: CAD/CAM fabrication accuracy of long- vs. short-span implant-supported FDPs.
abstract: OBJECTIVE
  To compare the precision of fit of long-span vs. short-span implant-supported screw-retained fixed dental prostheses (FDPs) made from computer-aided-design/computer-aided-manufactured (CAD/CAM) titanium and veneered with ceramic. The null hypothesis was that there is no difference in the vertical microgap between long-span and short-span FDPs.
  
  
  METHODS
  CAD/CAM titanium frameworks for an implant-supported maxillary FDP on implants with a flat platform were fabricated on one single master cast. Group A consisted of six 10-unit FDPs connected to six implants (FDI positions 15, 13, 11, 21, 23, 25) and group B of six 5-unit FDPs (three implants, FDI positions 21, 23, 25). The CAD/CAM system from Biodenta Swiss AG (Berneck, Switzerland) was used for digitizing (laser scanner) the master cast and anatomical CAD of each framework separately. The frameworks were milled (CAM) from a titanium grade V monobloc and veneered with porcelain. Median vertical distance between implant and FDP platforms from the non-tightened implants (one-screw test on implant 25) was calculated from mesial, buccal, and distal scanning electron microscope measurements.
  
  
  RESULTS
  All measurements showed values <40 μm. Total median vertical microgaps were 23 μm (range 2-38 μm) for group A and 7 μm (4-24 μm) for group B. The difference between the groups was statistically significant at implant 21 (P = 0.002; 97.5% CI -27.3 to -4.9) and insignificant at implant 23 (P = 0.093; -3.9 to 1.0).
  
  
  CONCLUSIONS
  CAD/CAM fabrication including laboratory scanning and porcelain firing was highly precise and reproducible for all long- and short-span FDPs. While all FDPs showed clinically acceptable values, the short-span FDPs were statistically more precise at the 5-unit span distance.
authors.affiliation: Department of Prosthodontics, School of Dental Medicine, University of Bern, Bern, Switzerland; Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, PA, USA.
authors.forename: Joannis
authors.initials: J
authors.lastname: Katsoulis
authors.forename: Philipp
authors.initials: P
authors.lastname: Müller
authors.forename: Regina
authors.initials: R
authors.lastname: Mericske-Stern
authors.forename: Markus B
authors.initials: MB
authors.lastname: Blatz
mesh_terms: D002516:Ceramics; D017076:Computer-Aided Design; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003801:Dental Veneers; D006801:Humans; D066298:In Vitro Techniques; D007575:Jaw, Edentulous / Q000534:rehabilitation; D008437:Maxilla; D008855:Microscopy, Electron, Scanning; D014025:Titanium
chemical_list: D015921:Dental Implants; D014025:Titanium
keywords: CAD/CAM; fixed dental prosthesis FDP; framework misfit; implant-supported; long-span; passive fit; short-span