title: Fit of lithium disilicate crowns fabricated from conventional and digital impressions assessed with micro-CT.
abstract: BACKGROUND
  Although the number of lithium disilicate crowns fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) technology has increased, the accuracy of the prostheses produced by using digital pathways remains unknown.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to compare marginal and internal discrepancies of lithium disilicate crowns fabricated from digital and conventional impressions.
  
  
  METHODS
  A typodont mandibular first molar was prepared for a lithium disilicate crown, and 20 duplicate dies were fabricated by milling poly(methyl methacrylate) resin blocks from laboratory scans. Four groups of 5 lithium disilicate crowns each were created by using a CS3500 (Carestream Dental) intraoral digital impression; Trios (3shape) intraoral digital impression; Ceramill Map400 (Amann Girrbach) extraoral digital impression; and a heat-press technique as a control group. All of the IPS e.max CAD (Ivoclar Vivadent AG) crowns were produced using a 5-axis milling engine (Ceramill Motion2). The lithium disilicate crowns were cemented with zinc phosphate cement under finger pressure. Marginal and internal discrepancies were measured using micro-computed tomography (SkyScan1172). One-way ANOVAs with the Tukey honest significant differences test were used for statistical analysis of the data (α=.05).
  
  
  RESULTS
  The mean marginal discrepancies of CS3500 lithium disilicate crowns were 129.6 μm, 200.9 μm for Ceramill Map400, and 207.8 μm 176.1 μm for the heat-press technique; and the internal discrepancy volumes for CS3500 were 25.3 mm3, 40.7 mm3for Trios, 29.1 mm3for Ceramill Map400, and 29.1 and 31.4 mm3for the heat-press technique. The CS3500 group showed a significantly better marginal discrepancy than the other 3 groups and a smaller internal discrepancy volume than the Trios group (P<.05).
  
  
  CONCLUSIONS
  Significant differences were found between IPS e.max CAD crowns produced using 2 intraoral digital impressions, whereas no differences were found between IPS e.max CAD crowns produced from an extraoral digital impression and IPS e.max Press crowns produced using a heat-press technique.
authors.affiliation: Graduate student, Department of Prosthodontics, College of Dentistry, Wonkwang University, Iksan, Korea.
authors.forename: Jae-Hyun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Assistant Fellow, Department of Prosthodontics, College of Dentistry, Wonkwang University, Iksan, Korea.
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Jeong
authors.affiliation: Associate Professor, Department of Prosthodontics, College of Dentistry, Wonkwang University, Iksan, Korea.
authors.forename: Jin-Han
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Professor, Department of Prosthodontics, College of Dentistry, Wonkwang University, Iksan, Korea. Electronic address: hwcho@wku.ac.kr.
authors.forename: Hye-Won
authors.initials: HW
authors.lastname: Cho
mesh_terms: D017076:Computer-Aided Design; D003442:Crowns / Q000592:standards; D003761:Dental Impression Technique; D003776:Dental Porcelain / Q000627:therapeutic use*; D017267:Dental Prosthesis Design / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D012117:Resins, Synthetic / Q000627:therapeutic use; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D012117:Resins, Synthetic; C493120:lithia disilicate; D003776:Dental Porcelain