title: Fatigue limit of polycrystalline zirconium oxide ceramics: Effect of grinding and low-temperature aging.
abstract: The following study aimed to evaluate the effect of grinding and low-temperature aging on the fatigue limit of Y-TZP ceramics for frameworks and monolithic restorations. Disc specimens from each ceramic material, Lava Frame (3M ESPE) and Zirlux FC (Ivoclar Vivadent) were manufactured according to ISO:6872-2008 and assigned in accordance with two factors: (1) "surface treatment"-without treatment (as-sintered, Ctrl), grinding with coarse diamond bur (181µm; Grinding); and (2) "low-temperature aging (LTD)" - presence and absence. Grinding was performed using a contra-angle handpiece under constant water-cooling. LTD was simulated in an autoclave at 134°C under 2-bar pressure for 20h. Mean flexural fatigue limits (20,000 cycles) were determined under sinusoidal loading using stair case approach. For Lava ceramic, it was observed a statistical increase after grinding procedure and different behavior after LTD stimuli (Ctrl<Grinding; Ctrl<Ctrl Ltd; Grinding=Grinding Ltd); while for Zirlux, grinding and low-temperature aging promoted a statistical increase in the fatigue limit (Ctrl<Grinding; Ctrl<Ctrl Ltd; Grinding<Grinding Ltd). An important increase was observed in m-phase content after both stimuli (grinding and LTD), although with different intensities. Additionally, fatigue test did not promote increase of m-phase content. Thus, tested grinding and low temperature aging did not damage the fatigue limit values significantly for both materials evaluated, even though those conditions promoted increase in m-phase.
authors.affiliation: PhD Graduate Program in Oral Science, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil; Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, The Netherlands. Electronic address: gabrielkrpereira@hotmail.com.
authors.forename: G K R
authors.initials: GKR
authors.lastname: Pereira
authors.affiliation: Faculty of Odontology, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil. Electronic address: taissilvestri@yahoo.com.
authors.forename: T
authors.initials: T
authors.lastname: Silvestri
authors.affiliation: Graduate Program in Dentistry, University of Taubaté, Taubaté, Brazil. Electronic address: marinamaral_85@yahoo.com.br.
authors.forename: M
authors.initials: M
authors.lastname: Amaral
authors.affiliation: PhD Graduate Program in Oral Science, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: M P
authors.initials: MP
authors.lastname: Rippe
authors.affiliation: Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, The Netherlands. Electronic address: c.kleverlaan@acta.nl.
authors.forename: C J
authors.initials: CJ
authors.lastname: Kleverlaan
authors.affiliation: PhD Graduate Program in Oral Science, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil. Electronic address: lfvalandro@hotmail.com.
authors.forename: L F
authors.initials: LF
authors.lastname: Valandro
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D008422:Materials Testing; D013499:Surface Properties; D013696:Temperature; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide
keywords: Fatigue; Grinding; Low-temperature degradation; Mechanical cycling; Zirconium oxide partially stabilized by yttrium