title: Relative translucency of six all-ceramic systems. Part I: core materials.
abstract: BACKGROUND
  All-ceramic restorations have been advocated for superior esthetics. Various materials have been used to improve ceramic core strength, but it is unclear whether they affect the opacity of all-ceramic systems.
  
  
  OBJECTIVE
  This study compared the translucency of 6 all-ceramic system core materials at clinically appropriate thicknesses.
  
  
  METHODS
  Disc specimens 13 mm in diameter and 0.49 +/- 0.01 mm in thickness were fabricated from the following materials (n = 5 per group): IPS Empress dentin, IPS Empress 2 dentin, In-Ceram Alumina core, In-Ceram Spinell core, In-Ceram Zirconia core, and Procera AllCeram core. Empress and Empress 2 dentin specimens also were fabricated and tested at a thickness of 0.77 +/- 0.02 mm (the manufacturer's recommended core thickness is 0.8 mm). A high-noble metal-ceramic alloy (Porc. 52 SF) served as the control, and Vitadur Alpha opaque dentin was used as a standard. Sample reflectance (ratio of the intensity of reflected light to that of the incident light) was measured with an integrating sphere attached to a spectrophotometer across the visible spectrum (380 to 700 nm); 0-degree illumination and diffuse viewing geometry were used. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white (Yw) backing to give Yb/Yw with CIE illuminant D65 and a 2-degree observer function (0.0 = transparent, 1.0 = opaque). One-way analysis of variance and Tukey's multiple-comparison test were used to analyze the data (P<.05).
  
  
  RESULTS
  Contrast ratios in order of most translucent to most opaque were as follows: Vitadur Alpha 0.60 +/- 0.03, Empress (0.5 mm) 0.64 +/- 0.01, In-Ceram Spinell 0.67 +/- 0.02, Empress 2 (0.5 mm) 0.68 +/- 0.02, Empress (0.8 mm) 0.72 +/- 0.01, Procera 0.72 +/- 0.01, Empress 2 (0.8 mm) 0.74 +/- 0.01, In-Ceram Alumina 0.87 +/- 0.01, In-Ceram Zirconia 1.00 +/- 0.01, and 52 SF alloy 1.00 +/- 0.00.
  
  
  CONCLUSIONS
  Within the limitations of this study, there was a range of ceramic core translucency at clinically relevant core thicknesses. In order of decreasing translucency, the ranges were Vitadur Alpha dentin (standard) > In-Ceram Spinell > Empress, Procera, Empress 2 > In-Ceram Alumina > In-Ceram Zirconia, 52 SF alloy.
authors.affiliation: School of Dentistry and Dows Institute for Dental Research, University of Iowa, Iowa City, Iowa, USA. mheffernan@ureach.com
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Heffernan
authors.forename: Steven A
authors.initials: SA
authors.lastname: Aquilino
authors.forename: Ana M
authors.initials: AM
authors.lastname: Diaz-Arnold
authors.forename: Debra R
authors.initials: DR
authors.lastname: Haselton
authors.forename: Clark M
authors.initials: CM
authors.lastname: Stanford
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Vargas
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry*; D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008027:Light; D008277:Magnesium Oxide / Q000737:chemistry; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D055095:Optics and Photonics; D010984:Platinum / Q000737:chemistry; D011176:Post and Core Technique; D013053:Spectrophotometry; D013223:Statistics as Topic; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry
chemical_list: C105314:AllCeram; D000538:Aluminum Silicates; D003764:Dental Materials; D006047:Gold Alloys; C075815:IPS-Empress ceramic; D016876:Metal Ceramic Alloys; D008903:Minerals; C111130:spinell; C111324:vitadur alpha omega; D003776:Dental Porcelain; C070870:In-Ceram; D008277:Magnesium Oxide; D010984:Platinum; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide