title: Surface properties of monolithic zirconia after dental adjustment treatments and in vitro wear simulation.
abstract: OBJECTIVE
  To investigate the surface properties (roughness, composition, phase transformation) of monolithic zirconia specimens after dental adjustment procedures (grinding, polishing) and wear simulation.
  
  
  METHODS
  Zirconia specimens (Cercon base, Cercon ht, DeguDent, G; n=10/material) were successively sintered, ground, and polished with an intraoral polishing kit in a three-step procedure. Sintered zirconia specimens with high surface roughness served as a reference. For each treatment step, wear simulations with steatite plates (d=10 mm) as antagonists were conducted as well as surface roughness tests (Ra), EDX analysis, and X-ray diffraction (XRD) measurements. SEM pictures were taken, and data were statistically analyzed (one-way ANOVA, post hoc Bonferroni, α=0.05).
  
  
  RESULTS
  Grinding significantly (p=0.000) increased the roughness of sintered zirconia up to values of 1.36±0.11 μm (Ra). Polishing significantly (p=0.000) reduced Ra. The lowest roughness value after the final polishing step was 0.20±0.03 μm. Wear testing resulted in a further slight decrease of Ra. After the grinding procedure, SEM pictures showed deep grooves that were progressively smoothed by polishing. The EDX spectra showed that magnesium was transferred from steatite antagonists to zirconia by wear. In the XRD-patterns, monoclinic (m) peaks were observed after grinding and polishing. The maximum intensity ratio between the m (11-1) peak and the tetragonal t (111) peak decreased after the completion of all polishing steps. Wear did not induce phase transformation.
  
  
  CONCLUSIONS
  Adequate polishing reduced the roughness of ground zirconia. Wear had little influence on roughness and no influence on phase transformation.
  
  
  CONCLUSIONS
  Careful polishing is recommended to keep surface roughness and phase transformation low.
authors.affiliation: Department of Prosthetic Dentistry, Regensburg University Medical Center, Regensburg, Germany. Electronic address: verena.preis@ukr.de.
authors.forename: Verena
authors.initials: V
authors.lastname: Preis
authors.affiliation: Institute for Experimental and Applied Physics, University of Regensburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schmalzbauer
authors.affiliation: Institute for Experimental and Applied Physics, University of Regensburg, Germany.
authors.forename: Dominique
authors.initials: D
authors.lastname: Bougeard
authors.affiliation: Department of Prosthetic Dentistry, Regensburg University Medical Center, Regensburg, Germany.
authors.forename: Sibylle
authors.initials: S
authors.lastname: Schneider-Feyrer
authors.affiliation: Department of Prosthetic Dentistry, Regensburg University Medical Center, Regensburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Rosentritt
mesh_terms: D002516:Ceramics / Q000737:chemistry / Q000627:therapeutic use; D003764:Dental Materials / Q000737:chemistry* / Q000627:therapeutic use; D003775:Dental Polishing; D003776:Dental Porcelain / Q000737:chemistry* / Q000627:therapeutic use; D019554:Dental Restoration Wear; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry* / Q000627:therapeutic use
chemical_list: D003764:Dental Materials; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Adjustment; Monolithic zirconia; Phase transformation; Polishing; Roughness; Wear