Nucleation efficacy and flexural strength of novel leucite glass-ceramics

Michael J Cattell; Christian Patzig; Sami Bissasu; Andreas Tsoutsos; Natalia Karpukhina

doi:10.1016/j.dental.2020.03.017

Nucleation efficacy and flexural strength of novel leucite glass-ceramics

Dent Mater. 2020 May;36(5):592-602. doi: 10.1016/j.dental.2020.03.017. Epub 2020 Apr 19.

Authors

Michael J Cattell¹, Christian Patzig², Sami Bissasu³, Andreas Tsoutsos³, Natalia Karpukhina³

Affiliations

¹ Centre for Oral Bioengineering, Bart's and the London School of Medicine and Dentistry, Queen Mary University of London, Turner Street, Whitechapel E1 2AD, UK. Electronic address: m.cattell@qmul.ac.uk.
² Fraunhofer Institute for Microstructure of Materials and Systems IMWS, Walter-Huelse-Strasse 1, 06120 Halle (Saale), Germany.
³ Centre for Oral Bioengineering, Bart's and the London School of Medicine and Dentistry, Queen Mary University of London, Turner Street, Whitechapel E1 2AD, UK.

PMID: 32317110
DOI: 10.1016/j.dental.2020.03.017

Abstract

Objectives: To optimize the nucleation mechanism in leucite glass-ceramics to allow more efficacious glass-ceramic manufacture and improvements in microstructure and mechanical reliability.

Materials and methods: An alumino-silicate glass was designed and synthesized using melt quench methods. The glass was crushed and milled using various milling times (48-93h) and spray drying. Nucleation and growth heat treatment schedules were applied to synthesize glass-ceramics. Glass/glass-ceramic powders and frit specimens were characterized using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR) and X-ray diffraction analyses (XRD). Glass-ceramic specimens were tested using the biaxial flexural strength test (BFS).

Results: Application of defined nucleation heat treatments resulted in the synthesis of Na/Ca titanates. NMR indicated changes to the ²³Na glass spectra in the nucleated glass and TEM/EDX the presence of Na/Ca/Ti domains (<200nm) within the leucite crystals and associated with the nucleation of the leucite phase. XRD confirmed the presence of a bulk leucite phase in the glass-ceramics. SEM/TEM confirmed the crystallization of the leucite phase (65.5-69.3%) in a thermally matched glass, in conjunction with the nano Na/Ca titanate phase. The leucite glass-ceramics resulted in a high BFS (255-268MPa), with reduction in powder milling time prior to heat treatments having no significant effect on flexural strength and reliability (p>0.05).

Significance: Na/Ca titanates were synthesized in leucite glass-ceramics for the first time and associated with its nucleation and efficacious growth. This nucleation optimization provides opportunities for more efficient manufacturing and microstructural/mechanical reliability improvements. Improved synthesis of high strength/reliable leucite glass-ceramics is useful for construction of esthetic minimally invasive restorations.

Keywords: Crystallization; Flexural strength; Glass-ceramic; NMR; Tetragonal leucite; Transmission electron microscopy; X-ray diffraction.

Publication types

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

MeSH terms

Aluminum Silicates
Ceramics
Dental Porcelain*
Flexural Strength*
Materials Testing
Microscopy, Electron, Scanning
Reproducibility of Results
Surface Properties

Substances

Aluminum Silicates
Dental Porcelain
leucite