Mechanical Performance and Fracture Behavior of Fixed Dental Prostheses Under Bending Loads: An In Vitro Comparative...

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Mechanical Engineering

Background:

• Fixed dental prostheses (FDPs) increasingly use high-strength ceramics.
• Understanding their fracture behavior under flexural loading is crucial.
• Current knowledge on FDP material performance under bending is incomplete.

Purpose of the Study:

• To compare the mechanical performance and fracture mechanisms of four FDP material systems.
• To evaluate CAD/CAM-fabricated three-unit FDPs made from metal-ceramic, zirconia-ceramic, monolithic zirconia, and monolithic lithium disilicate.
• To assess material behavior under standardized three-point bending conditions.

Main Methods:

• Fabrication of three-unit FDPs using CAD/CAM from four material groups (n=9 per group).
• Three-point bending test to failure, recording crack initiation load, maximum load, displacement, and stiffness.
• Fracture analysis using stereomicroscopy, micro-computed tomography (μCT), and scanning electron microscopy (SEM).

Main Results:

• Metal-ceramic FDPs (P1) had the highest loads (crack initiation: 0.89 kN, max: 1.91 kN) with veneer delamination.
• Monolithic zirconia FDPs (P3) showed the most brittle failure with abrupt fracture.
• Lithium disilicate (P4) demonstrated better resistance to catastrophic failure (F_max = 0.94 kN) than zirconia-ceramic (P2).

Conclusions:

• Monolithic zirconia FDPs' mechanical reliability under flexural load needs reassessment.
• Fracture behavior is critical for material selection, not just peak strength.
• Metal-ceramic and lithium disilicate FDPs showed more damage-tolerant responses in this in vitro study.