title: Effects of the sintering conditions of dental zirconia ceramics on the grain size and translucency.
abstract: OBJECTIVE
  This study aimed to identify the effects of the sintering conditions of dental zirconia on the grain size and translucency.
  
  
  METHODS
  Ten specimens of each of two commercial brands of zirconia (Lava and KaVo) were made and sintered under five different conditions. Microwave sintering (MS) and conventional sintering (CS) methods were used to fabricate zirconia specimens. The dwelling time was 20 minutes for MS and 20 minutes, 2, 10, and 40 hours for CS. The density and the grain size of the sintered zirconia blocks were measured. Total transmission measurements were taken using a spectrophotometer. Two-way analysis of variance model was used for the analysis and performed at a type-one error rate of 0.05.
  
  
  RESULTS
  There was no significant difference in density between brands and sintering conditions. The mean grain size increased according to sintering conditions as follows: MS-20 min, CS-20 min, CS-2 hr, CS-10 hr, and CS-40 hr for both brands. The mean grain size ranged from 347-1,512 nm for Lava and 373-1,481 nm for KaVo. The mean light transmittance values of Lava and KaVo were 28.39-34.48% and 28.09-30.50%, respectively.
  
  
  CONCLUSIONS
  Different sintering conditions resulted in differences in grain size and light transmittance. To obtain more translucent dental zirconia restorations, shorter sintering times should be considered.
authors.affiliation: Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
authors.forename: Mi-Jin
authors.initials: MJ
authors.lastname: Kim
authors.forename: Jin-Soo
authors.initials: JS
authors.lastname: Ahn
authors.forename: Ji-Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Hae-Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Woong-Chul
authors.initials: WC
authors.lastname: Kim
keywords: Grain size; Sintering; Translucency; Transmittance; Y-TZP; Zirconia