Fracture, roughness and phase transformation in CAD/CAM milling and subsequent surface treatments of lithium metasilicate/disilicate glass-ceramics

Abdur Rasheed Alao, Richard Stoll, Xiao Fei Song, John R. Abbott, Yu Zhang, Jaafar Abduo, Ling Yin

Research output: Contribution to journalArticle

Abstract

This paper studied surface fracture, roughness and morphology, phase transformations, and material removal mechanisms of lithium metasilicate/disilicate glass ceramics (LMGC/LDGC) in CAD/CAM-milling and subsequent surface treatments. LMGC (IPS e.max CAD) blocks were milled using a chairside dental CAD/CAM milling unit and then treated in sintering, polishing and glazing processes. X-ray diffraction was performed on all processed surfaces. Scanning electron microscopy (SEM) was applied to analyse surface fracture and morphology. Surface roughness was quantitatively characterized by the arithmetic average surface roughness Ra and the maximum roughness Rz using desktop SEM-assisted morphology analytical software. The CAD/CAM milling induced extensive brittle cracks and crystal pulverization on LMGC surfaces, which indicate that the dominant removal mechanism was the fracture mode. Polishing and sintering of the milled LMGC lowered the surface roughness (ANOVA, p < 0.05), respectively, while sintering also fully transformed the weak LMGC to the strong LDGC. However, polishing and glazing of LDGC did not significantly improve the roughness (ANOVA, p > 0.05). In comparison of all applied fabrication process routes, it is found that CAD/CAM milling followed by polishing and sintering produced the smoothest surface with Ra = 0.12 ± 0.08 µm and Rz = 0.89 ± 0.26 µm. Thus it is proposed as the optimized process route for LMGC/LDGC in dental restorations. This route enables to manufacture LMGC/LDGC restorations with cost effectiveness, time efficiency, and improved surface quality for better occlusal functions and reduced bacterial plaque accumulation.

Original languageEnglish (US)
Pages (from-to)251-260
Number of pages10
JournalJournal of the Mechanical Behavior of Biomedical Materials
Volume74
DOIs
StatePublished - Oct 1 2017

Fingerprint

Glass ceramics
Computer aided manufacturing
Lithium
Surface treatment
Computer aided design
Surface roughness
Phase transitions
Polishing
Sintering
Restoration
Scanning electron microscopy
Cost effectiveness
Analysis of variance (ANOVA)
Surface properties
Cracks
Fabrication
X ray diffraction
Crystals

Keywords

  • CAD/CAM milling
  • Fracture
  • Lithium metasilicate/disilicate glass-ceramics
  • Material removal mechanisms
  • Roughness
  • Surface treatments

ASJC Scopus subject areas

  • Biomaterials
  • Biomedical Engineering
  • Mechanics of Materials

Cite this

Fracture, roughness and phase transformation in CAD/CAM milling and subsequent surface treatments of lithium metasilicate/disilicate glass-ceramics. / Alao, Abdur Rasheed; Stoll, Richard; Song, Xiao Fei; Abbott, John R.; Zhang, Yu; Abduo, Jaafar; Yin, Ling.

In: Journal of the Mechanical Behavior of Biomedical Materials, Vol. 74, 01.10.2017, p. 251-260.

Research output: Contribution to journalArticle

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AB - This paper studied surface fracture, roughness and morphology, phase transformations, and material removal mechanisms of lithium metasilicate/disilicate glass ceramics (LMGC/LDGC) in CAD/CAM-milling and subsequent surface treatments. LMGC (IPS e.max CAD) blocks were milled using a chairside dental CAD/CAM milling unit and then treated in sintering, polishing and glazing processes. X-ray diffraction was performed on all processed surfaces. Scanning electron microscopy (SEM) was applied to analyse surface fracture and morphology. Surface roughness was quantitatively characterized by the arithmetic average surface roughness Ra and the maximum roughness Rz using desktop SEM-assisted morphology analytical software. The CAD/CAM milling induced extensive brittle cracks and crystal pulverization on LMGC surfaces, which indicate that the dominant removal mechanism was the fracture mode. Polishing and sintering of the milled LMGC lowered the surface roughness (ANOVA, p < 0.05), respectively, while sintering also fully transformed the weak LMGC to the strong LDGC. However, polishing and glazing of LDGC did not significantly improve the roughness (ANOVA, p > 0.05). In comparison of all applied fabrication process routes, it is found that CAD/CAM milling followed by polishing and sintering produced the smoothest surface with Ra = 0.12 ± 0.08 µm and Rz = 0.89 ± 0.26 µm. Thus it is proposed as the optimized process route for LMGC/LDGC in dental restorations. This route enables to manufacture LMGC/LDGC restorations with cost effectiveness, time efficiency, and improved surface quality for better occlusal functions and reduced bacterial plaque accumulation.

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