title: Effect of hydrothermal treatment on light transmission of translucent zirconias.
abstract: BACKGROUND
  Studies of the light transmission of translucent zirconias after hydrothermal treatment are limited.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the effect of hydrothermal treatment on the light transmission of translucent zirconias for monolithic restorations.
  
  
  METHODS
  Four commercially available zirconia products, BruxZir Anterior Solid Zirconia (BruxAnt, BA), Lava Plus High Translucency (LPHT), Katana Zirconia Super Translucent (KST), and Katana Zirconia Ultra Translucent (KUT) were assessed and 1 type of lithium disilicate, e.max Press LT (LDLT) was used as a control. Plate specimens, 20×20×1 mm (n=80) for the translucency assessment were sectioned from postsintered zirconia bulk materials and ground with a #400-grit diamond wheel and coolant. The specimens were placed under hydrothermal conditions of 134°C at 0.2 MPa (n=5 per group at 0, 5, 50, and 100 hours). Percentage of total transmittance of light (Tt%) of each specimen was measured using a spectrophotometer with an integrating sphere. X-ray diffraction analyses were used to measure tetragonal-monoclinic phase transformation. Surfaces were examined by scanning electron microscopy and energy dispersive spectrometry. Data were analyzed using 2-way ANOVA followed by the Tukey test (α=.05).
  
  
  RESULTS
  The Tt% ranged from 6.5% to 28.3%. Group LDLT obtained significantly higher transmittance than other tested groups, whereas groups KST and KUT had significantly higher Tt% than groups BA and LPHT (P<.05). A statistically significant increase in the amount of monoclinic phase was revealed within all translucent zirconia groups (P<.05), and the increase in group LPHT was significantly higher than those of the other 3 translucent zirconias (P<.05). Minimal changes in the percentages of light transmittance were revealed after 100-hour hydrothermal treatment for all tested translucent zirconias and a lithium disilicate glass-ceramic control.
  
  
  CONCLUSIONS
  Hydrothermal treatment had minimal effects on the translucency of translucent zirconias. The tetragonal-monoclinic phase transformation rate of translucent zirconias was found to be low, except in group LPHT.
authors.affiliation: Graduate student, Graduate Prosthodontics, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash.
authors.forename: Armand
authors.initials: A
authors.lastname: Putra
authors.affiliation: Professor, Department of Restorative Dentistry, University of Washington School of Dentistry, Seattle, Wash. Electronic address: akchung@uw.edu.
authors.forename: Kwok-Hung
authors.initials: KH
authors.lastname: Chung
authors.affiliation: Research Associate Professor, Materials Science and Engineering, University of Washington School of Engineering, Seattle, Wash.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Flinn
authors.affiliation: MSE Lab Manager, Materials Science and Engineering, University of Washington School of Engineering, Seattle, Wash.
authors.forename: Tuesday
authors.initials: T
authors.lastname: Kuykendall
authors.affiliation: Assistant Professor, Biostatistics, Joseph J Zilber School of Public Health, University of Wisconsin, Milwaukee, Wis.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zheng
authors.affiliation: Visiting Lecturer, Department of Restorative Dentistry, University of Washington School of Dentistry, Seattle, Wash; and Adjunct Lecturer, Department of Crown and Bridge, School of Life Dentistry at Tokyo, the Nippon Dental University, Tokyo, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Harada
authors.affiliation: Professor, Department of Restorative Dentistry, University of Washington School of Dentistry, Seattle, Wash.
authors.forename: Ariel J
authors.initials: AJ
authors.lastname: Raigrodski
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D008027:Light; D008422:Materials Testing / Q000379:methods; D013053:Spectrophotometry; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; C023506:Glass ceramics; D015040:Zirconium; C028541:zirconium oxide