title: Effect of glazed and polished surface finishes on the friction coefficient of two low-fusing ceramics.
abstract: BACKGROUND
  All-ceramic and metal-ceramic dental restorations are potentially harmful because they may wear opposing enamel. Wear is a multifactorial process; however, laboratory procedures can minimize the wear process, thus benefiting clinicians and manufacturers.
  
  
  OBJECTIVE
  This in vitro investigation of wear evaluated the physical and tribological characteristics of 2 low-fusing ceramics and dental enamel.
  
  
  METHODS
  Quantitative and qualitative analyses of 2 low-fusing ceramics (IPS d.Sign and Vita Omega 900) and enamel were performed using scanning electron microscopy, x-ray diffraction, and energy-dispersive analyses. Each ceramic was tested using 20 disks (10 mm x 3 mm), of which 10 were glazed and 10 were polished. Ten polished enamel specimens (6 mm x 7 mm) served as the control. The specimens were submitted to a Vickers hardness test for 30 seconds using a 200 g load. The coefficient of friction was determined by using a pin-on-disk test without lubrication (5 N load, 600 seconds, 120 RPM). The data were analyzed using a 1-way analysis of variance and Sheffe analysis (alpha=.05).
  
  
  RESULTS
  The same chemical elements were found in both ceramics, and tetragonal leucite was the main component of the crystalline phases. The microhardness of the enamel was significantly different ( P <.05) between the glazed and polished ceramics. There was no significant difference found in the friction coefficient (mean +/- SD) of the enamel (0.286 +/- 0.174), glazed Vita Omega 900 (0.309 +/- 0.085), and glazed IPS d.Sign (0.253 +/- 0.068) specimens. The mean friction coefficient of the polished Vita Omega 900 (0.486 +/- 0.036) and IPS d.Sign (0.446 +/- 0.037) specimens was found to be significantly higher than the enamel and glazed specimens ( P <.05).
  
  
  CONCLUSIONS
  Both ceramics tested presented similar chemical-structural and tribological characteristics. When glazed, they showed tribological similarity to dental enamel.
authors.affiliation: Post-Graduate Program of Odontology, Lutheran University of Brazil, Canoas, Brazil.
authors.forename: Christian
authors.initials: C
authors.lastname: Schuh
authors.forename: Eder Julio
authors.initials: EJ
authors.lastname: Kinast
authors.forename: Elio
authors.initials: E
authors.lastname: Mezzomo
authors.forename: Myriam Pereira
authors.initials: MP
authors.lastname: Kapczinski
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003743:Dental Enamel / Q000648:ultrastructure; D003775:Dental Polishing; D003776:Dental Porcelain / Q000737:chemistry*; D019554:Dental Restoration Wear; D004577:Electron Probe Microanalysis; D017276:Friction; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; C110711:vita omega; D003776:Dental Porcelain; C078519:leucite