In vivo aging of zirconia dental ceramics - Part I: Biomedical grade 3Y-TZP

Andraž Kocjan; Jasna Cotič; Tomaž Kosmač; Peter Jevnikar

doi:10.1016/j.dental.2020.11.023

In vivo aging of zirconia dental ceramics - Part I: Biomedical grade 3Y-TZP

Dent Mater. 2021 Mar;37(3):443-453. doi: 10.1016/j.dental.2020.11.023. Epub 2020 Dec 14.

Authors

Andraž Kocjan¹, Jasna Cotič², Tomaž Kosmač³, Peter Jevnikar⁴

Affiliations

¹ Department for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
² Department of Prosthodontics, Faculty of Medicine, University of Ljubljana, Hrvatski trg 6, SI-1000 Ljubljana, Slovenia.
³ Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
⁴ Department of Prosthodontics, Faculty of Medicine, University of Ljubljana, Hrvatski trg 6, SI-1000 Ljubljana, Slovenia. Electronic address: peter.jevnikar@mf.uni-lj.si.

PMID: 33334584
DOI: 10.1016/j.dental.2020.11.023

Abstract

Objective: In vivo aging of biomedical grade 3Y-TZP ceramics in the oral environment was assessed and compared to artificially accelerated in vitro hydrothermal aging extrapolations at 37°C.

Methods: 88 discs were pressed and sintered (1450-1500°C) from two commercial 3Y-TZP compositions containing 0.25% Al₂O₃ to generate finer- and coarser-grained specimens. As-sintered (AS) and airborne-particle abraded (APA; 50μm Al₂O₃) surfaces were investigated. In vivo aging was performed by incorporating specimens in lingual flanges of complete dentures of 12 edentulous volunteers who wore them continuously for up to 24 months. For comparison, in vitro hydrothermal aging at 134°C was also performed and analysed by XRD and (FIB)-SEM. Data was statistically analysed with linear regression models.

Results: Finer and coarser-grained specimens exhibited statistically insignificant differences in aging in vivo. The monoclinic fraction (X_m) on AS surfaces abruptly increased to ∼8% after 6 months. The aging process then proceeded with slower linear kinetics (∼0.24%/month). After 24 months, X_m reached ∼12%. The calculated maximum transformed layer was 0.385μm representing one layer of transformed grains. APA surfaces were highly aging resistant. The initial X_m of ∼4.0% linearly increased by 0.03%/month in vivo. In vitro aging exhibited an initial induction period, followed by linear aging kinetics. Coarser-grained AS surfaces aged significantly faster than fine-grained (2.41%/h compared to 2.16%/h). APA discs aged at a rate of 0.3%/h in vitro. Microcracking within a single grain and pull-out of grain clusters were observed on aged AS surfaces.

Significance: Biomedical grade 3Y-TZP was susceptible to in vivo aging. After 2 years in vivo, the aging kinetics were almost 3-times faster than the generally accepted in vitro-in vivo extrapolation.

Keywords: 3Y-TZP; Airborne-particle abrasion; FIB-SEM; In vivo aging; Low-temperature degradation; Transformation zone depth; XRD; Zirconia ceramics.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aged
Ceramics
Dental Materials
Humans
Materials Testing
Surface Properties
Yttrium*
Zirconium*

Substances

Dental Materials
Yttrium
Zirconium
zirconium oxide