J Adv Prosthodont.  2014 Dec;6(6):462-467. 10.4047/jap.2014.6.6.462.

Mechanical properties of zirconia after different surface treatments and repeated firings

• Subasi MG
• Demir N
• Kara O
• Ozturk AN
• Ozel F

• KMID: 2284719
• DOI: http://doi.org/10.4047/jap.2014.6.6.462

Abstract

PURPOSE
This study investigated the influence of surface conditioning procedures and repeated firings on monoclinic content and strength of zirconia before cementation.
MATERIALS AND METHODS
Sintered bar-shaped zirconia specimens were subjected to no surface treatment (control), air abrasion, or grinding (n=21). Their roughness was evaluated using a profilometer, and microscope analysis was performed on one specimen of each group. Then, 2 or 10 repeated firings (n=10) were executed, the monoclinic content of specimens was analyzed by X-ray diffraction, and a three-point flexural strength test was performed. Surface roughness values were compared using one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests, the monoclinic content values were tested using Kruskal-Wallis and Mann-Whitney U tests, and the flexural strength values were tested using two-way ANOVA and Tukey HSD tests (P=.05). Spearman's correlation test was performed to define relationships among measured parameters.
RESULTS
Surface-treated specimens were rougher than untreated specimens and had a higher monoclinic content (P<.005), and the relationship between roughness and monoclinic content was significant (P<.000). Neither surface treatment nor firing significantly affected the flexural strength, but Weibull analysis showed that for the air-abraded samples the characteristic strength was significantly lower after the 10th firing than after the 2nd firing.
CONCLUSION
After firing, a negligible amount of monoclinic content remained on the zirconia surfaces, and rougher surfaces had higher monoclinic contents than untreated surfaces. Multiple firings could be performed if necessary, but the fracture probability could increase after multiple firings for rougher surfaces.

Keyword

Surface Treatment; Zirconium Oxide; Ceramics; X-ray diffraction; Flexural Strength

MeSH Terms

Cementation
Ceramics
Fires*
X-Ray Diffraction
Ceramics

Figure

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  Fig. 1 Three-point flexural strength test apparatus.

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  Fig. 2 SEM views of zirconia surfaces (×700). (A) Control, (B) Air-abraded, (C) Ground.

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