Fracture frequency of all-ceramic crowns during dynamic loading in a chewing simulator using different loading and...

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• All-ceramic molar crowns are widely used in restorative dentistry.
• Understanding the fracture resistance of these materials under simulated oral conditions is crucial for clinical success.
• Dynamic loading and various luting protocols can influence the mechanical integrity of ceramic restorations.

Purpose of the Study:

• To compare the failure rates of IPS Empress and experimental e.max Press Exp all-ceramic molar crowns under dynamic loading.
• To evaluate the fracture load of these crowns under static loading after dynamic testing.
• To assess the influence of different dynamic loading and luting protocols on crown performance.

Main Methods:

• 144 molar crowns (IPS Empress or e.max Press Exp) were luted on PMMA abutments using Variolink or glass-ionomer cement (GIC).
• Crowns underwent dynamic loading in a chewing simulator with thermocycling, using sinusoidal or rectangular force profiles.
• Non-fractured crowns were subjected to static compression loading; control groups were also tested.

Main Results:

• No fractures occurred in the e.max Press Exp crowns, while IPS Empress crowns exhibited fractures and cracks.
• Sinusoidal force profiles significantly increased fractures in IPS Empress crowns compared to rectangular profiles.
• Luting protocol significantly affected fracture load, with greater variability in IPS Empress compared to e.max Press Exp.

Conclusions:

• Dynamic loading is essential for evaluating the clinical performance of all-ceramic molar crowns.
• The sinusoidal force profile is recommended for dynamic testing of ceramic crowns.
• e.max Press Exp demonstrates superior fracture resistance compared to IPS Empress under the tested conditions.