Surface fractures in pre-crystallized and crystallized zirconia-containing lithium silicate glass-ceramics generated in ultrasonic vibration-assisted machining

Afifah Z Juri; Xiao-Fei Song; Yoshitaka Nakanishi; James Dudley; Lisa Jamieson; Ling Yin

doi:10.1016/j.jmbbm.2023.106132

Surface fractures in pre-crystallized and crystallized zirconia-containing lithium silicate glass-ceramics generated in ultrasonic vibration-assisted machining

J Mech Behav Biomed Mater. 2023 Nov:147:106132. doi: 10.1016/j.jmbbm.2023.106132. Epub 2023 Sep 19.

Authors

Afifah Z Juri¹, Xiao-Fei Song², Yoshitaka Nakanishi³, James Dudley⁴, Lisa Jamieson⁴, Ling Yin⁵

Affiliations

¹ School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia; Department of Mechanical and Manufacturing Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia.
² Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, School of Mechanical Engineering, Tianjin University, Tianjin, 300354, China.
³ Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan.
⁴ Adelaide Dental School, The University of Adelaide, Adelaide, SA, 5005, Australia.
⁵ School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia. Electronic address: ling.yin@adelaide.edu.au.

PMID: 37776763
DOI: 10.1016/j.jmbbm.2023.106132

Abstract

Machining-induced surface fractures in ceramic restorations is a long-standing problem in dentistry, affecting the restorations' functionality and reliability. This study approached a novel ultrasonic vibration-assisted machining technique to zirconia-containing lithium silicate glass-ceramics (ZLS) and characterized its induced surface fracture topographies and morphologies to understand the microstructure-property-processing relations. The materials were processed using a digitally controlled ultrasonic milling machine at a harmonic vibration frequency with different amplitudes. Machining-induced surface fracture topographies were measured with a 3D white light optical profilometer using the arithmetic mean, peak and valley, and maximum heights, as well as the kurtosis and skewness height distributions, and the texture aspect ratios. Fracture morphologies were analysed using scanning electron microscopy (SEM). The surface fracture topographies were significantly dependent on the material microstructure, the mechanical properties, and the ultrasonic machining vibration amplitudes. Larger scale fractures with higher arithmetic mean, peak and valley heights, and kurtosis and skewness height distributions were induced in higher brittleness indexed pre-crystallized ZLS than lower indexed crystallized ZLS by conventional machining. Conchoidal fractures occurred in pre-crystallized ZLS while microcracks were found in crystallized state although brittle fractures mixed with localized ductile flow deformations dominated all machined ZLS surfaces. Ultrasonic machining at an ideal vibration amplitude resulted in more ductile removal, reducing fractured-induced peaks and valleys for both materials than conventional processing. This research demonstrates the microstructure-property-processing interdependence for ZLS materials and the novel machining technique to be superior to current processing, reducing fractures in the materials and potentially advancing dental CAD/CAM techniques.

Keywords: 3D topography; Fracture; Morphology; Ultrasonic vibration-assisted machining; Zirconia-containing lithium silicate glass-ceramics.