title: Effect of particle size on the flexural strength and phase transformation of an airborne-particle abraded yttria-stabilized tetragonal zirconia polycrystal ceramic.
abstract: BACKGROUND
  Because airborne-particle abrasion is an efficient method of improving the bond at the zirconia-cement interface, understanding its effect on the strength of yttria-stabilized tetragonal zirconia polycrystal is important.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effect of the particle size used for airborne-particle abrasion on the flexural strength and phase transformation of a commercially available yttria-stabilized tetragonal zirconia polycrystal ceramic.
  
  
  METHODS
  For both flexural strength (20.0 × 4.0 × 1.2 mm) (n=14) and phase transformation (14.0-mm diameter × 1.3-mm thickness) (n=4), the zirconia specimens were made from Lava, and their surfaces were treated in the following ways: as-sintered (control); with 50-μm aluminum oxide (Al2O3) particles; with 120-μm Al2O3 particles; with 250-μm Al2O3 particles; with 30-μm silica-modified Al2O3 particles (Cojet Sand); with 120-μm Al2O3 particles, followed by 110-μm silica-modified Al2O3 particles (Rocatec Plus); and with Rocatec Plus. The phase transformation (%) was assessed by x-ray diffraction analysis. The 3-point flexural strength test was conducted in artificial saliva at 37°C in a mechanical testing machine. The data were analyzed by 1-way ANOVA and the Tukey honestly significant difference post hoc test (α=.05).
  
  
  RESULTS
  Except for the Cojet Sand group, which exhibited statistically similar flexural strength to that of the as-sintered group and for the group abraded with 250-μm Al2O3 particles, which presented the lowest strength, airborne-particle abrasion with the other particle sizes provided the highest values, with no significant difference among them. The as-sintered specimens presented no monoclinic phase. The groups abraded with smaller particles (30 μm and 50 μm) and those treated with the larger ones (110 μm and/or 120 μm particles and 250 μm) exhibited percentages of monoclinic phase that varied from 4% to 5% and from 8.7% to 10%.
  
  
  CONCLUSIONS
  Except for abrasion with Cojet Sand, depending on the particle size, zirconia exhibited an increase or a decrease in its flexural strength. Airborne-particle abrasion promoted phase transformation (tetragonal to monoclinic), and the percentage of monoclinic phase varied according to the particle size.
authors.affiliation: Associate Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University - UNESP, Araraquara, São Paulo, Brazil. Electronic address: renata@foar.unesp.br.
authors.forename: Renata
authors.initials: R
authors.lastname: Garcia Fonseca
authors.forename: Filipe
authors.initials: F
authors.lastname: de Oliveira Abi-Rached
authors.forename: José Maurício
authors.initials: JM
authors.lastname: dos Santos Nunes Reis
authors.forename: Elisa
authors.initials: E
authors.lastname: Rambaldi
authors.forename: Paolo
authors.initials: P
authors.lastname: Baldissara
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D055598:Chemical Phenomena; D045662:Dental Etching / Q000379:methods*; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D010316:Particle Size; D018583:Pliability; D012464:Saliva, Artificial / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction / Q000295:instrumentation; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; D012464:Saliva, Artificial; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D012822:Silicon Dioxide; D015040:Zirconium; D000537:Aluminum Oxide