Forensic and reliability analyses of fixed dental prostheses.

Area of Science:

• Biomaterials science
• Dental materials science
• Mechanical engineering

Background:

• Implant-supported fixed dental prostheses (FDPs) are crucial for tooth replacement.
• Understanding FDP failure mechanisms is essential for improving longevity and patient outcomes.
• Previous studies have focused on material properties but lacked comprehensive failure analysis protocols.

Purpose of the Study:

• To establish a protocol for determining the failure cause of retrieved implant-supported FDPs.
• To correlate material properties with clinical performance in three-unit bridges.
• To identify the primary factors contributing to FDP failures in a clinical setting.

Main Methods:

• Loading of flexure bars of different veneer materials (leucite-reinforced, fluorapatite glass-ceramic) and Y-TZP zirconia core at varying stress rates.
• Fracture toughness determination using fast loading conditions.
• Fractal dimension measurements of flexure bars and FDPs to validate material property correlations.
• Failure analysis of clinically retrieved FDPs to identify fracture-initiating cracks.

Main Results:

• Fracture toughness values were determined for the tested veneer and zirconia materials.
• Fractal dimension measurements confirmed consistency between flexure bars and FDPs.
• The size of fracture-initiating cracks in failed FDPs was quantified.
• Clinical failures were attributed to repeated crack growth initiated by overload and subsequent use.

Conclusions:

• The developed protocol effectively determines FDP failure causes by linking material properties to clinical performance.
• Repeated crack growth due to initial overload and continuous use is the most probable cause of clinical FDP failures.
• This research provides valuable insights for designing more durable implant-supported fixed dental prostheses.