title: Two-body wear of different ceramic materials opposed to zirconia ceramic.
abstract: BACKGROUND
  Little is known about the wear behavior of ceramics opposed to unveneered zirconia and whether wear varies according to microstructure, surface toughness, and flexural strength of the ceramics.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the 2-body wear resistance of 5 ceramics opposing unveneered zirconia ceramic.
  
  
  METHODS
  Yttrium-stabilized zirconia, lithium disilicate glass ceramic, leucite-reinforced glass ceramic, fluorapatite glass ceramic, and nanofluorapatite glass ceramic specimens (n=8) were tested against standardized zirconia balls. Wear tests were performed in a dual-axis mastication simulator. Wear resistance was calculated by measuring the vertical and volumetric substance loss using a laser scanner. Specimen surfaces were evaluated at x50 and x500 magnification using SEM. Data were statistically analyzed using 1-way ANOVA and Fisher's exact test (alpha=.05).
  
  
  RESULTS
  Zirconia specimens demonstrated significantly lower vertical and volumetric loss than other ceramics (P<.05). The wear of fluorapatite and nanofluorapatite glass ceramics was significantly greater than that of leucite-reinforced and lithium disilicate glass ceramics (P<.05). SEM images showed no cracks or flaws in the zirconia and leucite-reinforced glass-ceramic specimens, indicating a mixture of attritional and adhesive wear. Other ceramic specimens exhibited cracks and chipped particle spaces which were consistent with fatigue wear. Zirconia demonstrated the lowest vertical and volumetric wear values. Leucite-reinforced and lithium disilicate glass ceramics demonstrated nonsignificant differences in volumetric wear, but these values were significantly lower than those observed for nanofluorapatite and fluorapatite glass ceramics (P<.05).
  
  
  CONCLUSIONS
  Wear varied according to the structure of the ceramic tested. Wear was of the fatigue type, and was significantly lowest in the zirconia specimens tested.
authors.affiliation: Department of Conservative Dentistry, Jordan University of Science and Technology, Irbid, Jordan. albashai@just.edu.jo
authors.forename: Zakereyya S M
authors.initials: ZS
authors.lastname: Albashaireh
authors.forename: Muhamad
authors.initials: M
authors.lastname: Ghazal
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D000704:Analysis of Variance; D001031:Apatites / Q000627:therapeutic use*; D003722:Dental Alloys / Q000627:therapeutic use; D003776:Dental Porcelain / Q000627:therapeutic use*; D017267:Dental Prosthesis Design; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D006801:Humans; D008409:Mastication; D018709:Statistics, Nonparametric; D015040:Zirconium / Q000627:therapeutic use*
chemical_list: D001031:Apatites; D003722:Dental Alloys; D003776:Dental Porcelain; D015040:Zirconium; C025105:fluorapatite; C028541:zirconium oxide