Load-Bearing Capacity of All-Ceramic Fixed Partial Dentures - Do In Vitro Tests Overestimate Strength?

Area of Science:

• Biomaterials Science
• Dental Materials
• Mechanical Engineering

Background:

• Monolithic zirconia is widely used for fixed dental prostheses (FDPs).
• In vitro testing is crucial for evaluating FDP performance.
• The influence of testing models on FDP load-bearing capacity requires further investigation.

Purpose of the Study:

• To evaluate how different testing models affect the load-bearing capacity of monolithic zirconia three-unit FDPs.
• To assess the clinical relevance of in vitro test results based on model variability.

Main Methods:

• Thirty-two CAD-designed, zirconia three-unit FDPs were fabricated.
• FDPs were resin-bonded to four distinct die models: PMMA (PM), fiberglass-reinforced polymer (FR), CoCr-alloy (NP), and tooth mobility simulation (TM).
• Load-to-failure testing was conducted, and data were statistically analyzed.

Main Results:

• Mean fracture values varied significantly across model types: TM (1676 MPa), PM (1820 MPa), FR (2266 MPa), and NP (4847 MPa).
• Significant differences were observed between most model groups, except for TM and PM.
• The choice of testing model demonstrably influences the measured fracture strength of ceramic FDPs.

Conclusions:

• The testing model significantly impacts the fracture load values of monolithic zirconia FDPs in vitro.
• Current in vitro testing methodologies may not accurately reflect clinical performance due to model variability.
• Developing highly standardized, clinically relevant testing methods is essential for reliable FDP evaluation.