Mechanical behavior of yttria-stabilized tetragonal zirconia polycrystal: Effects of different aging regimens

Content Provider	Directory of Open Access Journals (DOAJ)
Author	Luís Felipe GUILARDI Gabriel Kalil Rocha PEREIRA Vinícius Felipe WANDSCHER Marília Pivetta RIPPE Luiz Felipe VALANDRO
Abstract	Abstract This study aimed to characterize and compare the effect of different aging regimens on surface characteristic (topography and roughness), structural stability (phase transformation) and mechanical performance (Weibull analysis) of a Y-TZP ceramic. Discs (15 × 1.2 mm; VITA In-Ceram YZ) were prepared according to ISO 6872-2015 for biaxial flexural strength testing and randomly assigned into five groups (n = 30): as-sintered, no aging treatment (CTRL); 20 h in autoclave at 134°C, 2 bar pressure (AUT); intermittent mechanical loading at 20 Hz/106 load pulses (MechLoad); AUT followed by MechLoad (AUT+MechLoad); and storage in distilled water at 37°C, for 1 year (STO). The following analyses were performed: roughness (n = 30), surface topography (n = 2), phase transformation (n = 2) and biaxial flexure strength (n = 30). Phase transformation (increase of m-phase content) was shown to be a spontaneous, unavoidable and time-dependent process, occurring even under ambient conditions (dry storage after 1 year = 6.0% increase), and is considerably accelerated in the presence of moisture (STO = 17.6%; AUT= 63.1%; and AUT+MechLoad = 59.9%). For roughness parameters, only Ra was affected by aging, and the highest values were observed for AUT+MechLoad (0.25 ± 0.07 µm). For Weibull analysis, structural reliability (Weibull moduli) and characteristic strength were not impaired after aging, and some aging conditions led to increased values (highest weibull moduli in AUT, and highest characteristic strength in STO). Phase transformation proves to be a time-dependent spontaneous mechanism that is accelerated in the presence of different stimuli. However, none of the aging regimens had a negative effect on the characteristic strength and structural reliability of Y-TZP ceramic.
Related Links	http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1806-83242017000100280&lng=en&tlng=en
ISSN	18068324
e-ISSN	18073107
DOI	10.1590/1807-3107bor-2017.vol31.0094
Journal	Brazilian Oral Research
Volume Number	31
Language	English
Publisher	Sociedade Brasileira de Pesquisa Odontológica
Publisher Date	2017-01-01
Publisher Place	Brazil
Access Restriction	Open
Subject Keyword	Dentistry Dental Ceramics Zirconium Oxide Partially Stabilized By Yttrium Low-temperature Degradation Mechanical Properties Phase Transformation
Content Type	Text
Resource Type	Article