title: In vitro evaluation of the effect of core thickness and fabrication stages on the marginal accuracy of an all-ceramic system.
abstract: OBJECTIVE
  To evaluate the influence of core thickness and fabrication stages on the marginal accuracy of IPS e.max Press crowns.
  
  
  METHODS
  Twenty IPS e.max Press crowns, 1.5mm thick, were fabricated on metal dies. The crowns had two different core thicknesses, 0.8mm for group A and 1mm for group B, ten for each group. Marginal gap was measured after each stage of core fabrication, veneering and glaze firing. The specimens were not cemented and the measurements were made at four points on metal dies using a stereomicroscope (×120). Data were analyzed by SPSS software and independent t-test.
  
  
  RESULTS
  Mean marginal gaps measured after each stage for group A were 13.5 (±1.4) μm, 33.9 (±2.3) μm and 40.5(±1.7) μm, and for group B these figures were 14.9(±2.0) μm, 35.5(±2.2) μm and 41.3(±2.0) μm. There were no statistically significant differences in marginal gap values between the two groups (p>0.1). Significant increase in gap was observed after the veneering stage in both groups (p<0.05). After glazing, no significant increase in gap was detected.
  
  
  CONCLUSIONS
  IPS e.max Press crowns have an acceptable marginal fit. Increasing thickness of core does not increase marginal fitness.
authors.affiliation: Dental Research Center and Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: F
authors.initials: F
authors.lastname: Farid
authors.forename: H
authors.initials: H
authors.lastname: Hajimiragha
authors.forename: R
authors.initials: R
authors.lastname: Jelodar
authors.forename: A S
authors.initials: AS
authors.lastname: Mostafavi
authors.forename: H
authors.initials: H
authors.lastname: Nokhbatolfoghahaie
keywords: IPS e.max Press; Marginal Fitness; Marginal Gap