Reliability of metalloceramic and zirconia-based ceramic crowns

Area of Science:

• Dental materials science
• Biomaterials engineering
• Prosthodontics

Background:

• All-ceramic crowns are increasingly used, but their mechanical reliability compared to metal-ceramic restorations (MCR) is not fully established.
• Understanding the long-term performance of dental restorations under functional loads is crucial for clinical success.

Purpose of the Study:

• To compare the reliability of two Yttria-Tetragonal Zirconia Polycrystal (Y-TZP) all-ceramic crown systems against a metal-ceramic restoration (MCR) under mouth-motion fatigue.
• To test the hypothesis that MCR exhibit superior reliability compared to Y-TZP systems.

Main Methods:

• Fabrication of crowns using CAD on a master die simulating a mandibular first molar.
• Veneering of one Pd-Ag and two Y-TZP cores with porcelain.
• Cementation onto aged composite dies and subjecting crowns to mouth-motion fatigue testing.
• Determination of use-level probability using Weibull curves.

Main Results:

• Failure modes for all systems involved porcelain veneer chipping or fracture originating at the indentation site.
• Fatigue acted as an acceleration factor for the all-ceramic systems but not for the MCR.
• Metal-ceramic restorations demonstrated significantly higher reliability during cyclic mechanical testing.

Conclusions:

• Metal-ceramic restorations offer superior mechanical reliability over Y-TZP all-ceramic systems under simulated oral fatigue conditions.
• Y-TZP all-ceramic systems are more susceptible to fatigue-induced failure in a simulated oral environment.
• Clinical selection of crown systems should consider the demonstrated differences in mechanical reliability under functional stress.