title: Marginal and internal adaptation of ceramic crown restorations fabricated with CAD/CAM technology and the heat-press technique.
abstract: BACKGROUND
  The accuracy of chairside computer-aided design and computer-aided manufacturing (CAD/CAM) restorations is questionable, and the effect of the die spacer settings is not well stated in the literature.
  
  
  OBJECTIVE
  The purpose of the study was to evaluate the marginal and internal adaptation of E4D crowns fabricated with different spacer thicknesses and to compare these crowns with those fabricated with the heat-press technique.
  
  
  METHODS
  The E4D system was used to fabricate 30 crowns for the first 3 groups, with different spacer thickness settings: 30 μm, 60 μm, and 100 μm. In the fourth group, 10 lithium disilicate crowns were fabricated with the heat-press technique. The occlusal gap, axial gap, vertical marginal gap, and absolute marginal discrepancy were evaluated by x-ray microtomography. Statistical significance was assessed with the Kruskal-Wallis test (α=.05). For post hoc analyses, the Mann-Whitney U test was used alongside the Bonferroni correction for multiple comparisons (α=.008).
  
  
  RESULTS
  Within the CAD/CAM groups, the 30-μm spacer thickness resulted in the lowest median axial gap (90.04 μm), whereas the 60-μm spacer thickness resulted in the lowest median occlusal gap (152.39 μm). The median marginal gap values of the CAD/CAM-60 group (49.35 μm) and CAD/CAM-100 group (46.65 μm) were lower than those of the CAD/CAM-30 group (55.18 μm). No significant differences among the CAD/CAM groups were observed for absolute marginal discrepancy. The heat-press group had significantly different values than those of the CAD/CAM groups.
  
  
  CONCLUSIONS
  The spacer thickness and fabrication technique affected the adaptation of ceramic crowns. The heat-press group yielded the best marginal and internal crown adaptation results. The 30- or 60-μm spacer settings are recommended for the E4D CAD/CAM system.
authors.affiliation: Assistant Professor, Division of Prosthodontics, Department of Oral and Maxillofacial Rehabilitation, Faculty of Dentistry, King Abdulaziz University; Former Resident, Division of Postgraduate Prosthodontics, Department of Prosthodontics and Operative Dentistry, Tufts University School of Dental Medicine, Boston, Mass. Electronic address: dr.mously@gmail.com.
authors.forename: Hisham A
authors.initials: HA
authors.lastname: Mously
authors.affiliation: Assistant Professor, Department of Public Health and Community Service, Tufts University School of Dental Medicine, Boston, Mass.
authors.forename: Matthew
authors.initials: M
authors.lastname: Finkelman
authors.affiliation: Clinical Professor, Division of Postgraduate Prosthodontics, Department of Prosthodontics and Operative Dentistry, Tufts University School of Dental Medicine, Boston, Mass.
authors.forename: Roya
authors.initials: R
authors.lastname: Zandparsa
authors.affiliation: Professor, Division Head of Postgraduate Prosthodontics; Director, Graduate and Postgraduate Prosthodontics; Director, Advanced Education in Esthetic Dentistry; and Director, Advanced Dental Technology and Research Program, Tufts University School of Dental Medicine, Boston, Mass.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirayama
mesh_terms: D017076:Computer-Aided Design; D003442:Crowns; D003460:Crystallization; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D010781:Photography / Q000379:methods; D013499:Surface Properties; D013674:Technology, Dental; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: C508050:IPS e.max Press; C493120:lithia disilicate; D003776:Dental Porcelain