title: Surface roughness and the flexural and bend strength of zirconia after different surface treatments.
abstract: BACKGROUND
  Different surface treatments are commonly used during the fabrication of zirconia fixed dental prostheses. However, such treatments can affect the properties of the zirconia framework material.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to determine the effect of different surface treatments on the surface roughness and flexural and bend strength of zirconia.
  
  
  METHODS
  Seventy-two zirconia disks (n=8) and 72 zirconia bars (n=8) were sintered and divided into 9 groups for different surface treatments: sintered control, airborne-particle abraded with 50-μm aluminum oxide, airborne-particle abraded with Rocatec soft (30 μm), airborne-particle abraded with Rocatec (105 μm), grinding dry with a micromotor, turbine grinding under water cooling, grinding with silicon carbide paper, diamond paste polishing, and steam cleaning. The biaxial flexural strength of the disks (diameter 19 mm, thickness 1.6 mm) and 3-point bend test of the bars (thickness 2 mm, height 2 mm, length 25 mm) were measured dry at room temperature. One-way ANOVA followed by the Tukey HSD test (α=.05) and Pearson correlation test were used for statistical analysis.
  
  
  RESULTS
  Airborne-particle abrasion and silicon carbide paper grinding increased the flexural and bend strength of zirconia specimens (P<.05). The 3-point bend test gave 20% to 30% higher strength values than the biaxial test, but a strong correlation was shown between the test types. Surface roughness had a statistically significant negative effect on the strength values in the 3-point bend test.
  
  
  CONCLUSIONS
  The surface treatments tested affected the strength and surface roughness of zirconia framework material.
authors.affiliation: Assistant Professor, Department of Prosthetic Dentistry, University of Turku, Turku, Finland. Electronic address: jenhje@utu.fi.
authors.forename: Jenni
authors.initials: J
authors.lastname: Hjerppe
authors.affiliation: Professor, Department of Prosthetic Dentistry, University of Turku, Turku, Finland; and Professor, Clinic of Oral Diseases, Turku University Central Hospital, Turku, Finland.
authors.forename: Timo O
authors.initials: TO
authors.lastname: Närhi
authors.affiliation: Professor, Department of Biomaterials Science, University of Turku, Turku, Finland; and Professor, City of Turku, Welfare Division, Turku, Finland.
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
authors.affiliation: Laboratory Manager, Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland; and Senior Lecturer, Turku University of Applied Sciences, Faculty of Health and Well-being, Turku, Finland.
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
mesh_terms: D003775:Dental Polishing / Q000379:methods; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D013499:Surface Properties; D013718:Tensile Strength; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide