title: Accuracy of mechanical digitizing with a CAD/CAM system for fixed restorations.
abstract: OBJECTIVE
  Most research on the accuracy of dental computer-aided design/manufacturing (CAD/CAM) systems focuses on the marginal gap. A detailed analysis of the various components of CAD/CAM systems (digitizer, software, and milling machine) using this approach is nearly impossible. The purpose of this study was to determine the accuracy of the manual mechanical digitizer of the Precident-DCS system.
  
  
  METHODS
  Gauge blocks were aligned to the coordinate planes of the digitizer to determine the point and length measurement uncertainty. The values for each measuring point were compared for statistical differences concerning first versus second operator, pressure, and mode of sensing using analysis of variance. The measurement uncertainty was given by 95th percentiles.
  
  
  RESULTS
  The mean one-dimensional point measurement uncertainty in the Y direction was 11 microm for the first, 8 microm for the second, and 37 microm for both operators. The three-dimensional point measurement uncertainty in the Y direction was 10 microm for the first, 33 microm for the second, and 60 microm for both operators. The point measurement uncertainty was significantly influenced by the pressure during sensing and by the operator as well. There were significant differences between the first and second recordings. The length measurement uncertainty in the Y direction for a gauge block of 20 mm was 52 microm for both operators.
  
  
  CONCLUSIONS
  The reliability of the manually guided Precident-DCS digitizer is limited because of the significant influence of the operator and the mode of sensing (one or three dimensional). Compared with an automatic digitizing system, the measurement uncertainty of the manually guided digitizer exceeds the values published in the literature.
authors.affiliation: Department of Prosthetic Dentistry, Dresden University of Technology, University Hospital Carl Gustav Carus Dresden, Dental School, Germany. Ralph.Luthardt@mailbox.tu-dresden.de
authors.forename: R G
authors.initials: RG
authors.lastname: Luthardt
authors.forename: O
authors.initials: O
authors.lastname: Sandkuhl
authors.forename: V
authors.initials: V
authors.lastname: Herold
authors.forename: M H
authors.initials: MH
authors.lastname: Walter
mesh_terms: D000704:Analysis of Variance; D002138:Calibration; D003199:Computer Systems; D017076:Computer-Aided Design / Q000295:instrumentation / Q000592:standards* / Q000706:statistics & numerical data; D003793:Dental Restoration, Permanent / Q000592:standards; D006801:Humans; D015588:Observer Variation; D011312:Pressure; D011336:Probability; D015203:Reproducibility of Results; D012984:Software; D013223:Statistics as Topic; D013499:Surface Properties