title: An innovative method for evaluation of the 3-D internal fit of CAD/CAM crowns fabricated after direct optical versus indirect laser scan digitizing.
abstract: OBJECTIVE
  A procedure for 3-D analysis of the internal fit of fixed restorations has been developed. This study tested this method for investigating the fit of all-ceramic crowns.
  
  
  METHODS
  Twelve data sets of a prepared maxillary canine were acquired by direct digitizing of the metal master die (CEREC 3 camera) and by digitizing gypsum dies after conventional impression taking (CEREC 3 scan), respectively. Using these data sets, 24 all-ceramic single crowns each were machined out of two glass-ceramics. The method is based on duplicated gypsum dies of the metal master, which were made for each crown. The space between the duplicate die and the internal surface of the respective crown was filled with a low-viscosity addition silicone. These silicone films (replicas) and their corresponding dies were digitized in the same measuring position. The internal fit was calculated and quantitatively and qualitatively analyzed.
  
  
  RESULTS
  The mean and maximum positive deviations were 348 microm and 986 microm (camera), respectively, and 294 microm and 830 microm (scan), respectively, for Vitablocs Mk II and 332 microm and 920 microm (camera), respectively, and 307 microm and 852 microm (scan), respectively, for ProCAD. For both systems, the deviations were highest at the edges. CEREC scan yielded significantly better internal fit accuracy compared to the CEREC camera.
  
  
  CONCLUSIONS
  Evaluation of the internal 3-D fit using the innovative method proved to be suitable. Indirect data acquisition using impression taking showed improved internal fit compared with the direct procedure. However, the differences between the data-acquisition techniques are small compared to their absolute values.
authors.affiliation: Department of Prosthetic Dentistry, Dresden University of Technology, University Hospital Carl Gustav Carus Dresden, Dental School, Dresden, Germany. Ralph.Luthardt@mailbox.tu-dresden.de
authors.forename: Ralph G
authors.initials: RG
authors.lastname: Luthardt
authors.forename: Gido
authors.initials: G
authors.lastname: Bornemann
authors.forename: Susanne
authors.initials: S
authors.lastname: Lemelson
authors.forename: Michael H
authors.initials: MH
authors.lastname: Walter
authors.forename: Alfons
authors.initials: A
authors.lastname: Hüls
mesh_terms: D002133:Calcium Sulfate / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D003481:Cuspid; D003761:Dental Impression Technique; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D007834:Lasers; D003765:Models, Dental; D016628:Replica Techniques; D012828:Silicones / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003764:Dental Materials; C454801:ProCAD Ceramic; D012828:Silicones; C096477:Vitabloc MK1; D003776:Dental Porcelain; D002133:Calcium Sulfate