title: Circumferential fit assessment of CAD/CAM single crowns--a pilot investigation on a new virtual analytical protocol.
abstract: OBJECTIVE
  Techniques currently applied to determine the marginal accuracy of dental crown restorations yield inadequate information. This investigation aimed to test a new virtual approach for determining the precision of fit of single-crown copings.
  
  
  METHODS
  Zirconia single crown copings were manufactured on 10 gypsum, single-tooth master casts with two different established computer-aided design/computer-assisted manufacture (CAD/CAM) systems (groups A and B). After cementation, the circumferential fit was assessed with an industrial noncontact scanner and virtual 3D analysis, following a triple-scan protocol. Marginal fit was determined by virtual sectioning; each abutment-coping complex was digitally sliced in 360 vertical sections (1 degree per section). Standardized measurement distances for analyzing the marginal fit (z, xy, xyz) were selected, and a crosshair alignment was utilized to determine whether crowns were horizontally and/or vertically too large or small. The Mann-Whitney test was applied to test for differences between groups.
  
  
  RESULTS
  Significant differences in the xy direction (P = .008) were measured between groups. Group A showed a greater number of horizontally overextended margins and a higher frequency of xy distances greater than 150 Μm, in addition to a tendency for excessive z distances (P = .095).
  
  
  CONCLUSIONS
  The mean marginal gap values were clinically acceptable in the present investigation; however, a full circumferential analysis revealed significant differences in marginal coping quality.
authors.affiliation: University Clinic Erlangen-Nuremburg, Erlangen, Germany.
authors.forename: Ragai E
authors.initials: RE
authors.lastname: Matta
authors.forename: Johannes
authors.initials: J
authors.lastname: Schmitt
authors.forename: Manfred
authors.initials: M
authors.lastname: Wichmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Holst
mesh_terms: D002484:Cementation / Q000379:methods; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns / Q000592:standards; D000044:Dental Abutments; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design / Q000592:standards; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D003765:Models, Dental; D010865:Pilot Projects; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D014584:User-Computer Interface; D015040:Zirconium / Q000737:chemistry
chemical_list: D020099:Coated Materials, Biocompatible; D003764:Dental Materials; C009495:titanium dioxide; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide