title: Micro-computed tomography evaluation of marginal fit of lithium disilicate crowns fabricated by using chairside CAD/CAM systems or the heat-pressing technique.
abstract: BACKGROUND
  No consensus exists concerning the acceptable ranges of marginal fit for lithium disilicate crowns fabricated with either heat-pressing techniques or computer-aided design and computer-aided manufacturing (CAD/CAM) systems.
  
  
  OBJECTIVE
  The purpose of the study was to evaluate with micro-computed tomography the marginal fit of lithium disilicate crowns fabricated with different chairside CAD/CAM systems (Cerec or E4D) or the heat-pressing technique.
  
  
  METHODS
  Lithium disilicate crowns were fabricated to fit an in vitro cast of a single human premolar. Three fabrication techniques were used: digital impressions with Cerec 3D Bluecam scanner with titanium dioxide powder, followed by milling from IPS e.max CAD for Cerec; digital impressions with E4D Laser scanner without powder, followed by milling from IPS e.max CAD for E4D; and fabrication from IPS e.max Press by using the lost-wax and heat-pressing techniques. Each crown was fixed to the cast and scanned with micro-computed tomography to obtain 52 images for measuring the vertical and horizontal fit. Data were statistically analyzed by 1-way ANOVA, followed by the Tukey honestly significant difference test (α=.05).
  
  
  RESULTS
  The mean values of vertical misfit were 36.8 ±13.9 μm for the heat-pressing group and 39.2 ±8.7 μm for the Cerec group, which were significantly smaller values than for the E4D group at 66.9 ±31.9 μm (P=.046). The percentage of crowns with a vertical misfit <75 μm was 83.8% for Cerec and heat-pressing, whereas this value was 65% for E4D. Both types of horizontal misfit (underextended and overextended) were 49.2% for heat-pressing, 50.8% for Cerec, and 58.8% for E4D.
  
  
  CONCLUSIONS
  Lithium disilicate crowns fabricated by using the Cerec 3D Bluecam scanner CAD/CAM system or the heat-pressing technique exhibited a significantly smaller vertical misfit than crowns fabricated by using an E4D Laser scanner CAD/CAM system.
authors: Professor, Department of Occlusion, Fixed Prosthesis and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil. Electronic address: neves@triang.com.br.
authors: Flávio D
authors: FD
authors: Neves
authors: Professor, Department of Occlusion, Fixed Prosthesis and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.
authors: Célio J
authors: CJ
authors: Prado
authors: Graduate student, Department of Occlusion, Fixed Prosthesis and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.
authors: Marcel S
authors: MS
authors: Prudente
authors: Graduate student, Department of Occlusion, Fixed Prosthesis and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.
authors: Thiago A P N
authors: TA
authors: Carneiro
authors: Graduate student, Department of Occlusion, Fixed Prosthesis and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.
authors: Karla
authors: K
authors: Zancopé
authors: Professor, Department of Occlusion, Fixed Prosthesis and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.
authors: Letícia R
authors: LR
authors: Davi
authors: Professor, Department of Prosthodontics, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors: Gustavo
authors: G
authors: Mendonça
authors: Professor, Department of Prosthodontics, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors: Lyndon F
authors: LF
authors: Cooper
authors: Professor and Research Coordinator, Biomechanics Group, Department of Operative Dentistry and Dental Materials, School of Dentistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.
authors: Carlos José
authors: CJ
authors: Soares
mesh_terms: D017076:Computer-Aided Design; D003442:Crowns; D003735:Dental Casting Technique; D003761:Dental Impression Technique; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D006358:Hot Temperature; D006801:Humans; D007834:Lasers; D061848:Optical Imaging / Q000379:methods; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: C520133:IPS e.max CAD LT; C508050:IPS e.max Press; C493120:lithia disilicate; D003776:Dental Porcelain; C009495:titanium dioxide; D014025:Titanium