Influence of high-speed sintering protocols on translucency, mechanical properties, microstructure, crystallography, and low-temperature degradation of highly translucent zirconia

Hengyi Liu; Masanao Inokoshi; Kosuke Nozaki; Makoto Shimizubata; Hiroto Nakai; Thaw Di Cho Too; Shunsuke Minakuchi

doi:10.1016/j.dental.2021.12.028

Influence of high-speed sintering protocols on translucency, mechanical properties, microstructure, crystallography, and low-temperature degradation of highly translucent zirconia

Dent Mater. 2022 Feb;38(2):451-468. doi: 10.1016/j.dental.2021.12.028. Epub 2021 Dec 24.

Authors

Hengyi Liu¹, Masanao Inokoshi², Kosuke Nozaki³, Makoto Shimizubata¹, Hiroto Nakai¹, Thaw Di Cho Too¹, Shunsuke Minakuchi¹

Affiliations

¹ Department of Gerodontology and Oral Rehabilitation, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
² Department of Gerodontology and Oral Rehabilitation, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. Electronic address: m.inokoshi.gerd@tmd.ac.jp.
³ Department of Advanced Prosthodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.

PMID: 34961644
DOI: 10.1016/j.dental.2021.12.028

Abstract

Objectives: Impacts of high-speed sintering on the optical and mechanical properties, microstructure, crystallography, and low-temperature degradation of commercial yttria-partially stabilized zirconia (Y-PSZ) were investigated.

Methods: Five commercial Y-PSZ products (KATANA HT, KATANA STML, KATANA UTML, Zpex 4, and Zpex Smile) were investigated. Specimens were sintered following speed-sintering (~90 min) and conventional-sintering protocols (~7 h), and a group of KATANA STML was super-speed-sintered (18 min). Dimensions of the zirconia specimens after sintering were 14.5 mm (diameter) and 1.2 mm (thickness). Translucency was assessed using a colorimeter. Biaxial flexural strength was measured using a universal testing machine, followed by Weibull analysis. Scanning electron microscopy was used for microstructure assessments. X-ray diffraction was used to analyze the crystallography before and after hydrothermal aging. Low-temperature degradation (LTD) tests were performed at 134 °C under 2-3 bar water vapor in an autoclave.

Results: The translucency and flexural strength were not affected significantly by the sintering programs (p > 0.05). The conventionally sintered KATANA STML and speed-sintered Zpex 4 presented the highest and lowest Weibull modulus, respectively. The conventionally-sintered Y-PSZ had a larger average grain size and smaller fraction of fine grains than those of the speed-sintered specimens. The fractographic analysis of the speed- and conventionally sintered Y-PSZ yielded comparable results. The speed-sintered Y-PSZ exhibited a lower c-ZrO₂ content than that of conventionally-sintered Y-PSZ, except for KATANA HT and KATANA STML. LTD tests indicated that some of the speed and conventionally-sintered Y-PSZ exhibited similar monoclinic volume fractions.

Significance: Speed-sintering programs are acceptable for Y-PSZ zirconia.

Keywords: Flexural strength; Fractography; In vitro aging; Life data analysis; Optical property; Scanning electron microscopy (SEM); Size distribution; Speed-sintering; X-ray diffraction (XRD); Zirconium oxide.

Publication types

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

MeSH terms

Ceramics*
Crystallography
Dental Materials* / chemistry
Materials Testing
Surface Properties
Temperature
Yttrium
Zirconium / chemistry

Substances

Dental Materials
Yttrium
Zirconium
zirconium oxide