Raman Spectroscopy Evaluation of Subsurface Hydrothermal Degradation of Zirconia
The aims of this study were to calibrate the collection depth for
RMS and, using the calibration, to evaluate the in‐depth phase transformation induced in a dental 3 ‐ Y
ceramic by hydrothermal aging, simulating TZP LTD. Objectives 10x and 80x affording spatial resolutions of ~3 and ~1 μm, respectively, were used. Probe size was controlled by the confocal pinhole aperture. The collection depth of each probe (objective – pinhole
combination) was calibrated on a wedge‐shaped pure tetragonal zirconia specimen. Pure tetragonal samples of a dental 3 ‐ Y were aged in vitro in an autoclave, in Ringer solution, at 130°C,
under 0.6 MPa, for 10, 15, 20, 25, and 90 h. Two specimens were used for each time interval and two unexposed specimens served as controls. Monoclinic volume fraction (V
fm) was determined by X‐ray diffraction and by in‐depth probing with TZP RCMS.
Probes based on 10x objective penetrated up to 68 μm, whereas those based on the 80x were limited to 5 μm. Aging induced significant increase in V
fm, ranging from 30% after 10 h to 80% after 90 h. After 90 h aging, the 80% V
extended to at least 20 μm from the surface. A maximum V
fm was identified at 2.5 μm subsurface depth in 10, 15, and 20 h aged specimens.
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Document Type: Research Article
Publication date: July 1, 2012