title: Optical properties and light irradiance of monolithic zirconia at variable thicknesses.
abstract: OBJECTIVE
  The aims of this study were to: (1) estimate the effect of polishing on the surface gloss of monolithic zirconia, (2) measure and compare the translucency of monolithic zirconia at variable thicknesses, and (3) determine the effect of zirconia thickness on irradiance and total irradiant energy.
  
  
  METHODS
  Four monolithic partially stabilized zirconia (PSZ) brands; Prettau® (PRT, Zirkonzahn), Bruxzir® (BRX, Glidewell), Zenostar® (ZEN, Wieland), Katana® (KAT, Noritake), and one fully stabilized zirconia (FSZ); Prettau Anterior® (PRTA, Zirkonzahn) were used to fabricate specimens (n=5/subgroup) with different thicknesses (0.5, 0.7, 1.0, 1.2, 1.5, and 2.0mm). Zirconia core material ICE® Zircon (ICE, Zirkonzahn) was used as a control. Surface gloss and translucency were evaluated using a reflection spectrophotometer. Irradiance and total irradiant energy transmitted through each specimen was quantified using MARC® Resin Calibrator. All specimens were then subjected to a standardized polishing method and the surface gloss, translucency, irradiance, and total irradiant energy measurements were repeated. Statistical analysis was performed using two-way ANOVA and post-hoc Tukey's tests (p<0.05).
  
  
  RESULTS
  Surface gloss was significantly affected by polishing (p<0.05), regardless of brand and thickness. Translucency values ranged from 5.65 to 20.40 before polishing and 5.10 to 19.95 after polishing. The ranking from least to highest translucent (after polish) was: BRX=ICE=PRT<ZEN<KAT<PRTA (p<0.05). The ranking from least to highest total irradiant energy was: BRX<PRT<ICE=ZEN<KAT=PRTA (p<0.05). There was an inverse relationship between translucency, irradiant energy, and thickness of zirconia and the amount was brand dependent (p<0.05).
  
  
  CONCLUSIONS
  Brand selection, thickness, and polishing of monolithic zirconia can affect the ultimate clinical outcome of the optical properties of zirconia restorations. FSZ is relatively more polishable and translucent than PSZ.
authors.affiliation: Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland; Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC, USA. Electronic address: taabab@utu.fi.
authors.forename: Taiseer A
authors.initials: TA
authors.lastname: Sulaiman
authors.affiliation: Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland.
authors.forename: Aous A
authors.initials: AA
authors.lastname: Abdulmajeed
authors.affiliation: Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Terrence E
authors.initials: TE
authors.lastname: Donovan
authors.affiliation: Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: André V
authors.initials: AV
authors.lastname: Ritter
authors.affiliation: Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland; Department of Biomaterials Science, Institute of Dentistry, University of Turku, Turku, Finland.
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
authors.affiliation: Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland; Clinic of Oral Diseases, Turku University Central Hospital, Turku, Finland.
authors.forename: Timo O
authors.initials: TO
authors.lastname: Närhi
authors.affiliation: Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland; Department of Biomaterials Science, Institute of Dentistry, University of Turku, Turku, Finland.
authors.forename: Lippo V
authors.initials: LV
authors.lastname: Lassila
mesh_terms: D003764:Dental Materials / Q000737:chemistry*; D003775:Dental Polishing; D008027:Light; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; D019279:Resin Cements; D015040:Zirconium; C028541:zirconium oxide
keywords: Contrast ratio; Light cure irradiance; Monolithic zirconia; Surface gloss; Translucency parameter