Effect of low-temperature aging on the mechanical behavior of ground Y-TZP.
This study evaluated the effects of low-temperature aging on the surface topography, phase transformation, biaxial flexural strength, and structural reliability of a ground Y-TZP ceramic. Disc-shaped specimens were manufactured and divided according to two factors: "grinding" - without grinding (as-sintered, Ctrl), grinding with an extra-fine diamond bur (25 µm Xfine) and coarse diamond bur (181 µm Coarse); and "low-temperature-aging" (absence or presence). Grinding was performed using a contra-angle handpiece under water-cooling. Aging was performed in an autoclave at 134 °C, under 2 bar, over a period of 20 h. Surface topography analysis showed an increase in roughness based on grit-size (Coarse>Xfine>Ctrl), and aging promoted different effects on roughness (Ctrl Ag<Ctrl; Xfine Ag<Xfine; Coarse Ag>Coarse). Grinding and aging promoted an increase in the amount of m-phase, although different susceptibilities to degradation were observed. Weibull analysis showed an increase in characteristic strength after grinding (Coarse=Xfine>Ctrl); however, distinct effects were observed for aging (Ctrl<Ctrl Ag; Xfine=Xfine Ag; Coarse>Coarse Ag). Weibull moduli were statistically similar. Grinding promoted an increase in characteristic strength as a result of an increase in m-phase content; when the Y-TZP surface was ground by coarse diamond burs followed by aging, characteristic strength was reduced, meaning the low-temperature degradation appeared to intensify for rougher Y-TZP surfaces.
PhD Graduate Program in Oral Science (Prosthodontic Unit), Faculty of Odontology, Federal University of Santa Maria, Santa Maria, Brazil.
Gkr
G
Pereira
Faculty of Odontology, Science and Technology Institute, Sao Paulo State University (UNESP), São José dos Campos, Brazil.
M
M
Amaral
University of Sao Paulo (USP), Faculty of Odontology, Dept. of Biomaterials and Oral Biology, Sao Paulo, Brazil.
P F
PF
Cesar
Department of Restorative Dentistry (Division of Dental Biomaterials), Indiana University School of Dentistry, Indianapolis, IN, USA.
M C
MC
Bottino
Department of Dental Materials Science at ACTA, Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, The Netherlands.
C J
CJ
Kleverlaan
MSD-PhD Graduate Programs in Oral Science (Prosthodontic Unit), Faculty of Odontology, Federal University of Santa Maria, Santa Maria, Brazil. Electronic address: lfvalandro@hotmail.com.
L F
LF
Valandro
D055595:Mechanical Phenomena; D044367:Phase Transition; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium
Grinding; Hydrothermal aging; Low-temperature degradation; Mechanical properties; Phase transformation; Structural reliability; Zirconium oxide partially stabilized by yttrium