title: Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.
abstract: OBJECTIVE
  The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics.
  
  
  METHODS
  The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed.
  
  
  RESULTS
  The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p < 0.05). However, the mean bond strengths significantly decreased in the connector groups (CE and CV) after thermal cycling (p < 0.05). The elemental analysis suggested diffusion of ceramic substances into the zirconia surface.
  
  
  CONCLUSIONS
  A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.
authors: Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University , Seoul , South Korea.
authors: Hyung-In
authors: HI
authors: Yoon
authors: In-Sung
authors: IS
authors: Yeo
authors: Yang-Jin
authors: YJ
authors: Yi
authors: Sung-Hun
authors: SH
authors: Kim
authors: Jai-Bong
authors: JB
authors: Lee
authors: Jung-Suk
authors: JS
authors: Han
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D001031:Apatites / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D002858:Chromium Alloys / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D003799:Dental Stress Analysis; D003801:Dental Veneers; D004058:Diffusion; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D017680:Potassium Compounds / Q000737:chemistry; D033081:Shear Strength; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D001031:Apatites; D002858:Chromium Alloys; D003764:Dental Materials; D016876:Metal Ceramic Alloys; D017680:Potassium Compounds; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; C016447:feldspar; D015019:Yttrium; C023506:Glass ceramics; D015040:Zirconium; C025105:fluorapatite; C028541:zirconium oxide
keywords: Zirconia ceramic; interface; intermediate ceramic; thermocycling; veneer ceramic