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Effect of artificial aging on optical properties and crystalline structure of high translucency zirconia

J Prosthodont. 2023 Jan 14. doi: 10.1111/jopr.13648. Online ahead of print.


PURPOSE: To investigate the effect of different in vitro aging protocols on the optical properties and crystalline structure of high-translucency zirconia.

MATERIALS AND METHODS: Thirty-six specimens of high-translucency (HT) and extra-high translucency (XT) zirconia were divided into three groups: control (CO) – no treatment; hydrothermal aging (HA) – autoclave aging for 12.5 hours at 134°C, 2 bar; clinically-related aging (CRA) – aging in the chewing simulator for 1.2 million cycles, followed by 50,000 thermocycles (5-55°C) and immersion in HCl (pH 1.2) for 15 hours. Optical properties, crystalline structure, and surface roughness were analyzed and compared using Analysis of Variance (5% significance level).

RESULTS: There was no statistically significant effect of aging on translucency (p = 0.10), but CRA promoted the development of a high contrast ratio (p = 0.03). Aging did not cause significant color changes for HT (p = 0.65) or XT (p = 0.36). The proportion of monoclinic crystals increased to 40% for HT-zirconia after HA and 5% after CRA. No monoclinic crystals were detected for XT groups. There was no effect of aging on surface roughness (p = 0.77).

CONCLUSION: Although hydrothermal aging has been widely used to verify zirconia crystalline stability, it did not generate an effect similar to clinically-related aging on the optical properties and crystalline structure of zirconia. Hydrothermal aging affected the crystalline structure of HT-zirconia, and clinically-related aging compromised the optical properties of XT zirconia. This article is protected by copyright. All rights reserved.

PMID:36641491 | DOI:10.1111/jopr.13648

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