Fatigue Threshold R-Curves for Dental Lithium Disilicate Glass-Ceramics

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Ceramics

Background:

• All-ceramic dental restorations frequently fail due to inconspicuous chemical and mechanical fatigue, leading to fractures.
• This failure impacts patient prognosis, necessitates complex interventions, and incurs significant healthcare costs.
• Extending restoration lifespan beyond the patient's requires overcoming brittle material limitations against mechanical and environmental challenges.

Purpose of the Study:

• To investigate the relationship between crack size and strength in dental ceramics.
• To understand fatigue degradation mechanisms under simulated oral conditions.
• To correlate microstructural features with the fatigue resistance of glass-ceramics.

Main Methods:

• Utilized size-relevant, sharp precracked specimens with controlled geometry (truncated semielliptical crack).
• Employed the surface-crack-in-biaxial-flexure method and tangent method to derive quasi-static and cyclic resistance curves (R-curves).
• Analyzed stress-cycle data within a mechanistic framework to determine lifetime and fatigue parameters.

Main Results:

• Established a relationship between crack size and strength, and derived cyclic R-curve analogs.
• Demonstrated R-curve degradation in three dental lithium disilicate glass-ceramics up to 10 million cycles.
• Found that larger microstructural elements initially enhance quasi-static R-curves but lead to faster degradation.

Conclusions:

• Microstructure size is a critical factor influencing the fatigue resistance and degradation rate of dental glass-ceramics.
• Understanding these fatigue mechanisms is key to developing more durable all-ceramic restorations.
• Tailoring microstructure could optimize the balance between initial strength and long-term fatigue performance.