title: The effect of various veneering techniques on the marginal fit of zirconia copings.
abstract: OBJECTIVE
  This study aimed to evaluate the fit of zirconia ceramics before and after veneering, using 3 different veneering processes (layering, press-over, and CAD-on techniques).
  
  
  METHODS
  Thirty standardized zirconia CAD/CAM frameworks were constructed and divided into three groups of 10 each. The first group was veneered using the traditional layering technique. Press-over and CAD-on techniques were used to veneer second and third groups. The marginal gap of specimens was measured before and after veneering process at 18 sites on the master die using a digital microscope. Paired t-test was used to evaluate mean marginal gap changes. One-way ANOVA and post hoc tests were also employed for comparison among 3 groups (α=.05).
  
  
  RESULTS
  Marginal gap of 3 groups was increased after porcelain veneering. The mean marginal gap values after veneering in the layering group (63.06 µm) was higher than press-over (50.64 µm) and CAD-on (51.50 µm) veneered groups (P<.001).
  
  
  CONCLUSIONS
  Three veneering methods altered the marginal fit of zirconia copings. Conventional layering technique increased the marginal gap of zirconia framework more than pressing and CAD-on techniques. All ceramic crowns made through three different veneering methods revealed clinically acceptable marginal fit.
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Kianoosh
authors.initials: K
authors.lastname: Torabi
authors.affiliation: Biomaterial Research Center, Department of Prosthodontics, Faculty of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mahroo
authors.initials: M
authors.lastname: Vojdani
authors.affiliation: Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Rashin
authors.initials: R
authors.lastname: Giti
authors.affiliation: Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Masumeh
authors.initials: M
authors.lastname: Taghva
authors.affiliation: Department of Oral and Maxillofacial Pathology, Faculty of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Soheil
authors.initials: S
authors.lastname: Pardis
keywords: CAD-on; CAD/CAM; Layering; Marginal fit; Press-over; Zirconia