title: Influence of air-particle deposition protocols on the surface topography and adhesion of resin cement to zirconia.
abstract: OBJECTIVE
  This study evaluated the influence of air-particle abrasion protocols on the surface roughness (SR) of zirconia and the shear bond strength (SBS) of dual-polymerized resin cement to this ceramic.
  
  
  METHODS
  Sintered zirconia blocks (n = 115) (Lava, 3M ESPE) were embedded in acrylic resin and polished. The specimens were divided according to the 'particle type' (Al: 110 µm Al2O3; Si: 110 µm SiO2) and 'pressure' factors (2.5 or 3.5 bar) (n = 3 per group): (a) Control (no air-abrasion); (b) Al2.5; (c) Si2.5; (d) Al3.5; (e) Si3.5. SR (Ra) was measured 3-times from each specimen after 20 s of air-abrasion (distance: 10 mm) using a digital optical profilometer. Surface topography was evaluated under SEM analyses. For the SBS test, 'particle type', 'pressure' and 'thermocycling' (TC) factors were considered (n = 10; n = 10 per group): Control (no air-abrasion); Al2.5; Si2.5; Al3.5; Si3.5; ControlTC; Al2.5TC; Si2.5TC; Al3.5TC; Si3.5TC. After silane application, resin cement (Panavia F2.0) was bonded and polymerized. Specimens were thermocycled (6.000 cycles, 5-55°C) and subjected to SBS (1 mm/min). Data were analyzed using ANOVA, Tukey's and Dunnett tests (5%).
  
  
  RESULTS
  'Particle' (p = 0.0001) and 'pressure' (p = 0.0001) factors significantly affected the SR. All protocols significantly increased the SR (Al2.5: 0.45 ± 0.02; Si2.5: 0.39 ± 0.01; Al3.5: 0.80 ± 0.01; Si3.5: 0.64 ± 0.01 µm) compared to the control group (0.16 ± 0.01 µm). For SBS, only 'particle' factor significantly affected the results (p = 0.015). The SiO2 groups presented significantly higher SBS results than Al2O3 (Al2.5: 4.78 ± 1.86; Si2.5: 7.17 ± 2.62; Al3.5: 4.97 ± 3.74; Si3.5: 9.14 ± 4.09 MPa) and the control group (3.67 ± 3.0 MPa). All TC specimens presented spontaneous debondings. SEM analysis showed that Al2O3 created damage in zirconia in the form of grooves, different from those observed with SiO2 groups.
  
  
  CONCLUSIONS
  Air-abrasion with 110 µm Al2O3 resulted in higher roughness, but air-abrasion protocols with SiO2 promoted better adhesion.
authors.affiliation: Federal University of Pelotas, Pelotas Dental School, Department of Dental Materials , Pelotas , Brazil.
authors.forename: Hugo R
authors.initials: HR
authors.lastname: Sarmento
authors.forename: Fernanda
authors.initials: F
authors.lastname: Campos
authors.forename: Rafael S
authors.initials: RS
authors.lastname: Sousa
authors.forename: Joao P B
authors.initials: JP
authors.lastname: Machado
authors.forename: Rodrigo O A
authors.initials: RO
authors.lastname: Souza
authors.forename: Marco A
authors.initials: MA
authors.lastname: Bottino
authors.forename: Mutlu
authors.initials: M
authors.lastname: Ozcan
mesh_terms: D020906:Air Abrasion, Dental; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D019279:Resin Cements; D015040:Zirconium; C028541:zirconium oxide
keywords: Adhesion; aluminum oxide; roughness; scanning electron microscopy; shear strength; silicon dioxide; yttria stabilized tetragonal zirconia