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Brittle-Ductile Threshold in Lithium Disilicate under Sharp Sliding Contact
M Bawazir1,2, C H Lim1, P Arnés-Urgellés3
1Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Journal of Dental Research
|June 15, 2024
Summary
Researchers explored ductile-regime grinding to improve dental ceramic strength. They found a 70 mN threshold below which damage is avoided, paving the way for stronger ceramic restorations.
Area of Science:
- Materials Science
- Biomaterials Engineering
- Dental Ceramics
Background:
- Computer-aided design/computer-aided manufacturing (CAD/CAM) milling and grinding of dental ceramics can cause microfractures, weakening restorations.
- Current brittle-regime grinding is detrimental to ceramic strength.
- Ductile-regime grinding offers a potential solution for fabricating stronger ceramic dental restorations.
Purpose of the Study:
- To analyze damage caused by current brittle-regime grinding of dental ceramics.
- To investigate the potential of ductile-regime grinding as a safer and efficient alternative.
- To determine the brittle-ductile transition threshold load for lithium disilicate glass-ceramic.
Main Methods:
- Micro-scratch tests on lithium disilicate glass-ceramic (IPS e.max CAD) specimens.
- Biaxial flexure strength tests to assess strength degradation after scratching.
- Scanning electron microscopy (SEM) and focused ion beam (FIB) for surface and subsurface damage analysis.
Main Results:
- SEM revealed both ductile and brittle removal modes during scratching.
- A brittle-ductile transition threshold load of 70 mN was determined using FIB and strength tests.
- Specimens tested below 70 mN showed no strength degradation or subsurface cracks.
Conclusions:
- The brittle-ductile transition threshold is critical for damage-free ceramic processing.
- Ductile-regime grinding below 70 mN can prevent strength degradation in dental ceramics.
- This research lays the groundwork for developing damage-free ductile-regime milling protocols for dental restorations.
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