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J Biomed Mater Res B Appl Biomater. 2015 Oct;103(7):1519-23. doi: 10.1002/jbm.b.33334. Epub 2014 Dec 1.

Phase transformation of dental zirconia following artificial aging.

Author information

1
Department of Biomaterials, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama.
2
Department of Materials Science and Engineering, University of Alabama at Birmingham, Birmingham, Alabama.

Abstract

AIMS:

Low-temperature degradation (LTD) of yttria-stabilized zirconia can produce increased surface roughness with a concomitant decrease in strength. This study determined the effectiveness of artificial aging (prolonged boiling/autoclaving) to induce LTD of Y-TZP (yttria-tetragonal zirconia-polycrystals) and used artificial aging for transformation depth progression analyses. The null hypothesis is aging techniques tested produce the same amount of transformation, transformation is not time/temperature dependent and LTD causes a constant transformation throughout the Y-TZP samples.

METHODS:

Dental-grade Y-TZP samples were randomly divided into nine subgroups (n = 5): as received, 3.5 and 7 day boiling, 1 bar autoclave (1, 3, 5 h), and 2 bar autoclave (1, 3, 5 h). A 4-h boil treatment (n = 2) was performed post-experiment for completion of data. Transformation was measured using traditional X-ray diffraction and low-angle X-ray diffraction.

RESULTS:

The fraction of t → m transformation increased with aging time. The 3.5 day boil and 2 bar 5 h autoclave produced similar transformation results, while the 7 day boiling treatment revealed the greatest transformation. The surface layer of the aged specimen underwent the most transformation while all samples displayed decreasing transformation with depth.

SIGNIFICANCE:

Surface transformation was evident, which can lead to rougher surfaces and increased wear of opposing dentition/materials. Therefore, wear studies addressing LTD of Y-TZP are needed utilizing accelerated aging.

KEYWORDS:

X-ray diffraction; phase transformation; yttria stabilized; zirconia

PMID:
25448797
DOI:
10.1002/jbm.b.33334
[Indexed for MEDLINE]

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