title: Cycle-dependent in vitro wear performance of dental ceramics after clinical surface treatments.
abstract: OBJECTIVE
  To investigate the two-body wear performance of dental ceramics after different clinical surface treatments as a function of number of wear cycles.
  
  
  METHODS
  Standardized specimens (n=72/material) were prepared from two different zirconia ceramics, a veneering porcelain, and a lithiumdisilicate glass ceramic. Specimens were progressively glazed, ground, and polished. After each treatment step 24 specimens per material were kept at the obtained surface state. Steatite and human enamel specimens served as reference materials. Two-body wear tests were performed with steatite spheres as antagonists in a pin-on-block design (50N, 1.6 Hz, lateral movement: 1mm, mouth opening: 2mm) under simultaneous thermal cycling (5/55 °C, 2 min/cycle). For investigating the dynamic evolution of the wear process, 9 groups per material (n=8/group) were defined, differing in surface state (glazed, ground, and polished) and number of chewing cycles (40T, 80T, and 120T; T: ×1000): glazed 40T, glazed 80T, glazed 120T, ground 40T, ground 80T, ground 120T, polished 40T, polished 80T, polished 120T. Surface roughness, wear depth of the specimens and relative wear area of the steatite antagonists were determined using an optical 3D laser scanning microscope. SEM evaluation was done. Mean values and standard deviations were calculated and statistically analyzed (one-way ANOVA, post-hoc Bonferroni, α=0.05).
  
  
  RESULTS
  Veneering and lithiumdisilicate ceramics showed higher wear depths than zirconia ceramics (p<0.05). Wear of veneering and lithiumdisilicate ceramics and their antagonists increased with wear cycles but was only marginally influenced by the initial surface state. Wear of zirconia was not influenced by wear cycles but antagonists of zirconia showed a cycle-dependent wear increase. Polished zirconia surfaces showed lowest wear for material and antagonist. Wear mechanism of common ceramics was characterized by abrasive wear. Zirconia in contrast showed a superficial cyclic shifting of worn material of the antagonist.
  
  
  CONCLUSIONS
  Wear of zirconia and standard ceramics showed different wear performances, strongly influenced by surface treatments as well as number of wear cycles.
authors: Department of Prosthetic Dentistry, University Medical Center Regensburg, 93042 Regensburg, Germany. Electronic address: verena.preis@ukr.de.
authors: Verena
authors: V
authors: Preis
authors: Department of Prosthetic Dentistry, University Medical Center Regensburg, 93042 Regensburg, Germany.
authors: Katharina
authors: K
authors: Grumser
authors: Department of Prosthetic Dentistry, University Medical Center Regensburg, 93042 Regensburg, Germany.
authors: Sibylle
authors: S
authors: Schneider-Feyrer
authors: Department of Prosthetic Dentistry, University Medical Center Regensburg, 93042 Regensburg, Germany.
authors: Michael
authors: M
authors: Behr
authors: Department of Prosthetic Dentistry, University Medical Center Regensburg, 93042 Regensburg, Germany.
authors: Martin
authors: M
authors: Rosentritt
mesh_terms: D003776:Dental Porcelain / Q000737:chemistry*; D008422:Materials Testing; D055595:Mechanical Phenomena; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Dental ceramics; Roughness; Surface treatment; Two-body wear; Wear simulation; Zirconia