title: Wear performance of dental ceramics after grinding and polishing treatments.
abstract: OBJECTIVE
  The aim of this in vitro study was to determine the two-body wear resistance of different dental ceramics after grinding and polishing treatments.
  
  
  METHODS
  Standardized specimens were prepared from three zirconia and two veneering ceramics and were subjected to different surface treatments. Zirconia ceramics were polished, ground and repolished, veneering ceramics were ground and repolished. One zirconia ceramic was investigated with a superficial glaze. Human enamel was used for reference. Surface roughness R(a) was determined using a profilometric contact surface measurement device. Two-body wear tests were performed in a chewing simulator with steatite and enamel antagonists, respectively. Specimens were loaded pneumatically in a pin-on-block design for 1.2x10(5) mastication cycles (50 N, 1.2 Hz, lateral movement: 1 mm, mouth opening: 2 mm) under simultaneous thermal cycling (600 cycles, 5/55 °C). Wear depths of specimens were determined using a 3D laser scanning device, wear areas of steatite antagonists were measured by means of light-optical micrographs. Means and standard deviations were calculated, and statistical analysis was performed using one-way analysis of variance (ANOVA) and the Bonferroni multiple comparison test for post hoc analysis (α=0.05). Scanning electron microscopy was applied for evaluating the wear performance of ceramics and antagonists.
  
  
  RESULTS
  No wear was found for polished, ground and repolished zirconia. Compared to the wear depths of the enamel reference with 274.1±187.4 μm versus steatite and 123.3±131.0 μm versus enamel, relative wear depths of porcelains ranged between 0.54±0.07 and 0.62±0.09 with steatite antagonists and between 0.66±0.26 and 1.04±0.27 with enamel antagonists. Relative wear areas of steatite antagonists (enamel reference: 1.25 mm(2)) varied between 0.84±0.13 and 1.90±0.29 for zirconia and between 1.97±0.38 and 2.47±0.40 for porcelains. Enamel antagonists generally showed wear, cracks or even fractures, but revealed smooth surfaces when opposed to polished/ground/repolished zirconia and ploughed surfaces when opposed to ground/repolished porcelains or glaze.
  
  
  CONCLUSIONS
  Zirconia ceramics yielded superior wear behavior and lower antagonistic wear compared to porcelains. A trend to higher ceramic and antagonistic wear was shown after grinding treatments.
authors.affiliation: Department of Prosthetic Dentistry, University Medical Center Regensburg, 93042 Regensburg, Germany. verena.preis@ukr.de
authors.forename: Verena
authors.initials: V
authors.lastname: Preis
authors.forename: Michael
authors.initials: M
authors.lastname: Behr
authors.forename: Gerhard
authors.initials: G
authors.lastname: Handel
authors.forename: Sibylle
authors.initials: S
authors.lastname: Schneider-Feyrer
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hahnel
authors.forename: Martin
authors.initials: M
authors.lastname: Rosentritt
mesh_terms: D002516:Ceramics; D003743:Dental Enamel; D003776:Dental Porcelain; D019554:Dental Restoration Wear; D006801:Humans; D008277:Magnesium Oxide; D055595:Mechanical Phenomena; D012822:Silicon Dioxide; D013499:Surface Properties; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D008277:Magnesium Oxide; C089766:steatite; D012822:Silicon Dioxide; D015040:Zirconium; C028541:zirconium oxide