title: [Study on low temperature degradation of dental zirconia ceramic].
abstract: OBJECTIVE
  To evaluate the properties of low temperature degradation (LTD) of dental Y-TZP by experiments.
  
  
  METHODS
  According to ISO 13356-2008 standards, 72 blanks of Y-TZP were sintered at different temperature (1 400 °C,1 450 °Cor 1 530 °C) and in different heat preserving time(2 h or 5 h), and then the specimens were grounded and polished. The blanks were divided into 12 groups according to the different sintering temperature, heat preserving time and aging time. The surface of specimens was observed by SEM to evaluate the grain size of specimens; Each group of specimens was exposed to 140 °C hydrothermal aging environment for 0 h, 5 h or 24 h. After aging, XRD analysis was undertaken to determine the amount of phase transformation from tetragonal to monoclinic for each groups. At last, the biaxial flexural strengths of all specimens were measured and calculated.
  
  
  RESULTS
  The SEM showed that the grain size of each group of Y-TZP increased with the increase of sintering temperature and heat preserving time, however, all of them were below 1 μm. The XRD analysis showed the contents of monoclinic of each group varied with different sintering temperatures, heat preserving times and aging time. The flexural strength of 24 h aging groups declined significantly; but that of 5 h aging group showed increase or decrease according to the different sintering temperatures and heat preserving times.
  
  
  CONCLUSIONS
  Different sintering procedures to some extent may affect the Y-TZP aging properties.
authors.affiliation: Department of Stomatology, Beijing Jishuitan Hospital, Beijing 100035, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Pei Jun
authors.initials: PJ
authors.lastname: Lv
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
mesh_terms: D003080:Cold Temperature; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide