title: A comparative evaluation of the translucency of zirconias and lithium disilicate for monolithic restorations.
abstract: BACKGROUND
  Studies comparing the translucency of zirconias and lithium disilicates are limited.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to measure the translucency of recently developed translucent zirconias and compare them with lithium disilicate.
  
  
  METHODS
  Five types of zirconia, Prettau Anterior (Zirkonzahn GmbH), BruxZir (Glidewell Laboratories), Katana HT, Katana ST, and Katana UT (Kurary Noritake Dental Inc), and 1 type of lithium disilicate, e.max CAD LT (Ivoclar Vivadent AG), were assessed. Non-colored zirconia test specimens (n=5) were prepared as rectangles with dimensions of 15×10×0.5 and 15×10×1.0 mm. The shade of lithium disilicate was B1. A spectrophotometer (Evolution 300 UV-Vis) with an integrating sphere was used to evaluate the total transmittance of light as a percentage (Tt%) at a wavelength of 555 nm for comparison among groups. The Welch robust test for equality of means was used to compare group means (α=.025) and post hoc pairwise comparisons among groups were performed with the Dunnett T3 method.
  
  
  RESULTS
  For the 0.5 mm thickness groups, the Tt% was 31.90 ±0.49 for Prettau Anterior, 28.82 ±0.22 for BruxZir, 28.49 ±0.14 for Katana HT, 31.67 ±0.24 for Katana ST, 33.73 ±0.13 for Katana UT, and 40.32 ±0.25 for e-max CAD LT. Post hoc tests indicated that all groups were significantly different from each other, except for between BruxZir and Katana HT, and between Prettau Anterior and Katana ST. Katana UT was significantly more translucent than all other zirconias, and e-max CAD LT was significantly more translucent than all zirconias. For the 1.0 mm thickness groups, the Tt% was 22.58 ±0.41 for Prettau Anterior, 20.13 ±0.22 for BruxZir, 20.18 ±0.39 for Katana HT, 21.86 ±0.39 for Katana ST, 23.37 ±0.27 for Katana UT, and 27.05 ±0.56 for e-max CAD LT. Post hoc tests indicated that all materials were significantly different from each other, except for between BruxZir and Katana HT, and among Prettau Anterior, Katana ST and Katana UT which were significantly more translucent than all other zirconias and less translucent than e-max CAD LT.
  
  
  CONCLUSIONS
  At a thickness of 0.5 mm, Katana UT was significantly more translucent than all other zirconias, and e-max CAD LT was significantly more translucent than all zirconias. At a thickness of 1.0 mm, Prettau Anterior, Katana ST, and Katana UT were significantly more translucent than all other zirconias and less than e-max CAD LT.
authors.affiliation: Visiting Lecturer, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash; and Adjunct Lecturer, Department of Crown and Bridge, School of Life Dentistry at Tokyo, The Nippon Dental University, Tokyo, Japan. Electronic address: kosuke1004hrd@gmail.com.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Harada
authors.affiliation: Professor, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash.
authors.forename: Ariel J
authors.initials: AJ
authors.lastname: Raigrodski
authors.affiliation: Professor, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash.
authors.forename: Kwok-Hung
authors.initials: KH
authors.lastname: Chung
authors.affiliation: Research Associate Professor, Department of Materials Science and Engineering, University of Washington, Seattle, Wash.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Flinn
authors.affiliation: Assistant Professor, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash.
authors.forename: Sami
authors.initials: S
authors.lastname: Dogan
authors.affiliation: Research Associate Professor, Department of Oral Health Sciences, University of Washington, Seattle, Wash.
authors.forename: Lloyd A
authors.initials: LA
authors.lastname: Mancl
mesh_terms: D003776:Dental Porcelain / Q000737:chemistry*; D006801:Humans; D008027:Light; D008422:Materials Testing; D013053:Spectrophotometry; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry
chemical_list: C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide