title: Effect of particle deposition parameters on silica coating of zirconia using a chairside air-abrasion device.
abstract: OBJECTIVE
  To evaluate the effect of nozzle distance, nozzle angle, and deposition duration on the silica content attained on zirconia by air abrasion.
  
  
  METHODS
  Disk-shaped zirconia (LAVA, 3M ESPE) (diameter: 10 mm, thickness: 2 mm) specimens (N = 54) were obtained. They were wet-ground finished using 600-, 800-, and 1200-grit silicone carbide abrasive papers in sequence and ultrasonically cleaned. The specimens were mounted in a specially designed apparatus that allowed the chairside air-abrasion device to be operated under standard conditions. Alumina-coated silica particles (CoJet Sand, 3M ESPE) were deposited on the zirconia disk surfaces varying the following parameters: a) nozzle distance (2, 5, 10 mm), and b) deposition duration (5, 13, 20 s) at two nozzle angles (45 and 90 degrees) under 2.5 bar pressure at three locations on each ceramic disk. The specimen surfaces were then gently air dried for 20 s. Silica content in weight percentage (wt%) was measured from 3 surfaces on each disk using Energy Dispersive X-ray Spectroscopy (EDS) (150X) in an area of 0.8 mm x 0.6 mm (n = 3 per group). Surface topographies were evaluated using SEM. Data were analyzed using ANOVA and Tukey's tests (α = 0.05).
  
  
  RESULTS
  Nozzle angle (p = 0.003) and deposition duration (p = 0.03) significantly affected the results, but nozzle distance (p = 0.569) did not. A significantly higher amount of silica (wt%) was achieved when the nozzle angle was 45 degrees to the surface in all distance-duration combinations (16.7 to 28.2 wt%) compared to the 90-degree nozzle angle (10.7 to 18.6 wt%) (p < 0.001). The silica amount was significantly higher after 20-s deposition duration than after 13 s (p < 0.05). EDS analysis demonstrated not only Si but also Al, Zr, and O traces on the substrate. SEM images indicated that deposition at a nozzle distance of 2 mm often created cavitations in zirconia.
  
  
  CONCLUSIONS
  Effective silica deposition using a charside air-abrasion device can be achieved when the nozzle is held at 45 degrees to the surface with more than 2-mm nozzle distance for 20 s.
authors.affiliation: University of Zurich, Zurich, Switzerland. mutluozcan@hotmail.com
authors.forename: Mutlu
authors.initials: M
authors.lastname: Ozcan
authors.forename: John
authors.initials: J
authors.lastname: Raadschelders
authors.forename: Pekka
authors.initials: P
authors.lastname: Vallittu
authors.forename: Lippo
authors.initials: L
authors.lastname: Lassilla
mesh_terms: D000535:Aluminum / Q000032:analysis; D000537:Aluminum Oxide / Q000737:chemistry; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D045662:Dental Etching / Q000295:instrumentation* / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010100:Oxygen / Q000032:analysis; D011312:Pressure; D012825:Silicon / Q000032:analysis; D017655:Silicon Compounds / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D013997:Time Factors; D015040:Zirconium / Q000032:analysis / Q000737:chemistry*
chemical_list: D017554:Carbon Compounds, Inorganic; D003764:Dental Materials; D017655:Silicon Compounds; D012822:Silicon Dioxide; D015040:Zirconium; D000535:Aluminum; D000537:Aluminum Oxide; C028541:zirconium oxide; D010100:Oxygen; C022088:silicon carbide; D012825:Silicon