title: Air-particle abrasion on zirconia ceramic using different protocols: effects on biaxial flexural strength after cyclic loading, phase transformation and surface topography.
abstract: This study evaluated the effect of different air-particle abrasion protocols on the biaxial flexural strength and structural stability of zirconia ceramics. Zirconia ceramic specimens (ISO 6872) (Lava, 3M ESPE) were obtained (N=336). The specimens (N=118, n=20 per group) were randomly assigned to one of the air-abrasion protocols: Gr1: Control (as-sintered); Gr2: 50 µm Al2O3 (2.5 bar); Gr3: 50 µm Al2O3 (3.5 bar); Gr4: 110 µm Al2O3(2.5 bar); Gr5: 110 µm Al2O3 (3.5 bar); Gr6: 30 µm SiO2 (2.5 bar) (CoJet); Gr7: 30 µm SiO2(3.5 bar); Gr8: 110 µm SiO2 (2.5 bar) (Rocatec Plus); and Gr9: 110 µm SiO2 (3.5 bar) (duration: 20 s, distance: 10 mm). While half of the specimens were tested immediately, the other half was subjected to cyclic loading in water (100,000 cycles; 50 N, 4 Hz, 37 °°C) prior to biaxial flexural strength test (ISO 6872). Phase transformation (t→m), relative amount of transformed monoclinic zirconia (FM), transformed zone depth (TZD) and surface roughness were measured. Particle type (p=0.2746), pressure (p=0.5084) and cyclic loading (p=0.1610) did not influence the flexural strength. Except for the air-abraded group with 110 µm Al2O3 at 3.5 bar, all air-abrasion protocols increased the biaxial flexural strength (MPa) (Controlnon-aged: 1,030 ± 153, Controlaged: 1,138 ± 138; Experimentalnon-aged: 1,307 ± 184-1,554 ± 124; Experimentalaged: 1,308 ± 118-1,451 ± 135) in both non-aged and aged conditions, respectively. Surface roughness (Ra) was the highest with 110 µm Al2O3(0.84 µm. FM values ranged from 0% to 27.21%, higher value for the Rocatec Plus (110 µm SiO2) and 110 µm Al2O3 groups at 3.5 bar pressure. TZD ranged between 0 and 1.43 µm, with the highest values for Rocatec Plus and 110 µm Al2O3 groups at 3.5 bar pressure.
authors.affiliation: Department of Restorative Dentistry, Division of Prosthodontics, Federal University of Paraíba, 9216 Praia de Guajirú Avenue, 59092-220 Natal, Rio Grande do Norte, Brazil.
authors.forename: Rodrigo O A
authors.initials: RO
authors.lastname: Souza
authors.forename: Luiz F
authors.initials: LF
authors.lastname: Valandro
authors.forename: Renata M
authors.initials: RM
authors.lastname: Melo
authors.forename: João P B
authors.initials: JP
authors.lastname: Machado
authors.forename: Marco A
authors.initials: MA
authors.lastname: Bottino
authors.forename: Mutlu
authors.initials: M
authors.lastname: Ozcan
mesh_terms: D000388:Air; D002516:Ceramics / Q000737:chemistry*; D006358:Hot Temperature; D055595:Mechanical Phenomena; D044367:Phase Transition; D011312:Pressure; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015040:Zirconium; C028541:zirconium oxide
keywords: Air-abrasion; Biaxial flexural strength; Silica coating; Y-TZP; Zirconia