Effect of low-temperature degradation on the fatigue performance of dental strength-gradient multilayered zirconia restorations

Qiulan Li; Yunxu Yang; Kuangyao Chen; Yingyu Jiang; Michael V Swain; Mianfeng Yao; Ying He; Yujie Liang; Yutao Jian; Ke Zhao

doi:10.1016/j.jdent.2024.104866

Effect of low-temperature degradation on the fatigue performance of dental strength-gradient multilayered zirconia restorations

J Dent. 2024 Mar:142:104866. doi: 10.1016/j.jdent.2024.104866. Epub 2024 Jan 27.

Authors

Qiulan Li¹, Yunxu Yang¹, Kuangyao Chen¹, Yingyu Jiang¹, Michael V Swain², Mianfeng Yao³, Ying He¹, Yujie Liang⁴, Yutao Jian⁵, Ke Zhao⁶

Affiliations

¹ Hospital of Stomatology, Sun Yat-Sen University, Guangzhou 510055, China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou 510055, China.
² Don State Technical University, Rostov-on-Don 344000, Russia; AMME, Sydney University, Sydney, Australia.
³ Xiangya Hospital Central South University, Changsha 410008, China.
⁴ Hospital of Stomatology, Sun Yat-Sen University, Guangzhou 510055, China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou 510055, China. Electronic address: liangyj35@mail.sysu.edu.cn.
⁵ Guangdong Provincial Key Laboratory of Stomatology, Guangzhou 510055, China; Institute of Stomatology, Sun Yat-Sen University, Guangzhou 510055, China. Electronic address: jianyt@mail.sysu.edu.cn.
⁶ Hospital of Stomatology, Sun Yat-Sen University, Guangzhou 510055, China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou 510055, China. Electronic address: zhaoke@mail.sysu.edu.cn.

PMID: 38281620
DOI: 10.1016/j.jdent.2024.104866

Abstract

Objectives: Fatigue and low-temperature degradation (LTD) are the main factors contributing to zirconia restoration failure. This study evaluated the effect of LTD on the fatigue performance of the novel "strength & shade-gradient" multilayered zirconia restorations.

Methods: Discs (15 mm × 1.2 mm) of each yttria content layer from a newly developed strength-gradient multilayered zirconia were fabricated and under accelerated aging in an autoclave at 134℃ for 0 h, 32 h, and 64 h. Then, the phase transformation, microstructure, and mechanical properties after LTD were assessed. In addition, the crown samples, including the multi-Zir, 3Y-Zir, and 5Y-Zir were fabricated, and their monotonic and fatigue load before and after LTD, percentage of fatigue degradation (S_d) and the fracture morphology were investigated. Statistical analyses were performed using paired samples t-test (α' = α/3 = 0.017), one-way ANOVA and Weibull analysis.

Results: After LTD, the phase transformation, surface roughness, depth of transformed zone, and residual stress were increased and inversely associated with the yttria content. The indentation elastic modulus and hardness after LTD decreased; however, there was no significant difference between the different yttria content layers. The monotonic and fatigue load of multi-Zir restorations decreased, but their Weibull modulus increased, and S_d decreased, similar to 3Y-Zir. The crack origin was associated with the cervical region.

Conclusion: These results show that although LTD reduces the absolute fatigue strength of strength-gradient multilayered zirconia restorations, it also reduces the effect of cyclic fatigue itself on the strength of zirconia (relative to monotonic strength), which might be due to the increase of residual stress.

Clinical significance: The novel "strength & shade-gradient" multilayered zirconia restorations show a promising performance during in vitro LTD and fatigue test and their reliability to some extent is comparable to 3Y-Zir. Yet, further in vivo longitudinal studies are warranted to confirm their precise performance.

Keywords: Fatigue strength; Low-temperature degradation; Restorations; Yttria content; Zirconia.

MeSH terms

Ceramics
Dental Materials* / chemistry
Materials Testing
Reproducibility of Results
Surface Properties
Temperature
Yttrium* / chemistry
Zirconium / chemistry

Substances

Dental Materials
yttria
zirconium oxide
Yttrium
Zirconium