title: Marginal accuracy of titanium copings fabricated by casting and CAD/CAM techniques.
abstract: BACKGROUND
  Advances in computer-aided design/computer-assisted manufacturing (CAD/CAM) technology purportedly enhance the marginal fit of dental restorations. However, little information is available on the marginal accuracy of restorations manufactured with various CAD/CAM systems.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate and compare the marginal accuracy and refinement time of titanium copings fabricated by 3 different CAD/CAM systems relative to standard casting techniques.
  
  
  METHODS
  Sixty-four stone die duplicates of a human maxillary central incisor, prepared for a metal-ceramic crown, with a uniform chamfer design, were divided into 4 groups (n=16). The specimens were restored with titanium copings using CAD/CAM systems Pro 50 (PRO), DCS (DCS), and Everest (EVE). A conventional titanium casting technique, Biotan (BIO), served as a control. Vertical and horizontal discrepancies between restoration margins and the preparations were each measured before and after manual refinement. This refinement was completed using a disclosing agent and by removing the internal positive defects of the copings. The marginal discrepancies of the copings were evaluated at 4 standard areas using 10 measurements, for a total of 160 measurements of each margin. Repeated-measures ANOVA was used for analyzing marginal accuracy. The coping refinement time was analyzed with the Kruskal-Wallis and post hoc Wilcoxon rank sum tests (alpha=.05).
  
  
  RESULTS
  The marginal discrepancies (microm) ranged from 32.9 to 127.8 before and from 3.4 to 58.4 after the manual refinement of copings. Manual refinement significantly improved the marginal accuracy (P<.0001) when compared with the initial fabrication. The relative (%) gain of marginal accuracy was PRO, 74.1%; DCS, 69.7%; EVE, 68.7%; and the control, BIO, 69.2%. The median duration of manual refinement time in minutes was 6.0 for PRO, 9.5 for DCS, 4.0 for EVE, and 4.0 for BIO (Kruskal-Wallis-test: P<.0001).
  
  
  CONCLUSIONS
  Manual adjustment significantly improves the marginal accuracy of CAD/CAM system-fabricated titanium copings. The highest marginal accuracy was achieved with the DCS system, using a longer refinement time.
authors.affiliation: Department of Prosthodontics, School of Dentistry, University Hospital Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany. siegbert.witkowski@uniklinik-freiburg.de
authors.forename: Siegbert
authors.initials: S
authors.lastname: Witkowski
authors.forename: Futoshi
authors.initials: F
authors.lastname: Komine
authors.forename: Thomas
authors.initials: T
authors.lastname: Gerds
mesh_terms: D000704:Analysis of Variance; D017076:Computer-Aided Design; D003442:Crowns; D003735:Dental Casting Technique; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design / Q000379:methods*; D006801:Humans; D007180:Incisor; D016876:Metal Ceramic Alloys; D018709:Statistics, Nonparametric; D013997:Time Factors; D014025:Titanium
chemical_list: D016876:Metal Ceramic Alloys; D014025:Titanium