title: In vitro precision of fit of computer-aided design and computer-aided manufacturing titanium and zirconium dioxide bars.
abstract: OBJECTIVE
  Optical scanners combined with computer-aided design and computer-aided manufacturing (CAD/CAM) technology provide high accuracy in the fabrication of titanium (TIT) and zirconium dioxide (ZrO) bars. The aim of this study was to compare the precision of fit of CAD/CAM TIT bars produced with a photogrammetric and a laser scanner.
  
  
  METHODS
  Twenty rigid CAD/CAM bars were fabricated on one single edentulous master cast with 6 implants in the positions of the second premolars, canines and central incisors. A photogrammetric scanner (P) provided digitized data for TIT-P (n=5) while a laser scanner (L) was used for TIT-L (n=5). The control groups consisted of soldered gold bars (gold, n=5) and ZrO-P with similar bar design. Median vertical distance between implant and bar platforms from non-tightened implants (one-screw test) was calculated from mesial, buccal and distal scanning electron microscope measurements.
  
  
  RESULTS
  Vertical microgaps were not significantly different between TIT-P (median 16μm; 95% CI 10-27μm) and TIT-L (25μm; 13-32μm). Gold (49μm; 12-69μm) had higher values than TIT-P (p=0.001) and TIT-L (p=0.008), while ZrO-P (35μm; 17-55μm) exhibited higher values than TIT-P (p=0.023). Misfit values increased in all groups from implant position 23 (3 units) to 15 (10 units), while in gold and TIT-P values decreased from implant 11 toward the most distal implant 15.
  
  
  CONCLUSIONS
  CAD/CAM titanium bars showed high precision of fit using photogrammetric and laser scanners. In comparison, the misfit of ZrO bars (CAM/CAM, photogrammetric scanner) and soldered gold bars was statistically higher but values were clinically acceptable.
authors.affiliation: Department of Prosthodontics, School of Dental Medicine, University of Bern, Bern, Switzerland. joannis.katsoulis@zmk.unibe.ch
authors.forename: Joannis
authors.initials: J
authors.lastname: Katsoulis
authors.forename: Regina
authors.initials: R
authors.lastname: Mericske-Stern
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Yates
authors.forename: Naomi
authors.initials: N
authors.lastname: Izutani
authors.forename: Norbert
authors.initials: N
authors.lastname: Enkling
authors.forename: Markus B
authors.initials: MB
authors.lastname: Blatz
mesh_terms: D017076:Computer-Aided Design; D015921:Dental Implants; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D012994:Dental Soldering / Q000379:methods; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D007834:Lasers; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010780:Photogrammetry / Q000295:instrumentation; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D006047:Gold Alloys; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide
keywords: CAD/CAM; Laser scanner; Photogrammetry; Precision of fit; Titanium; Zirconium dioxide