An Approach to Improve Specimen Processing for the Flexural Strength Testing of Zirconia

Area of Science:

• Biomaterials Science
• Dental Materials
• Mechanical Engineering

Background:

• Accurate flexural strength measurement of zirconia is vital for dental restorative material selection and performance prediction.
• Significant variability in specimen preparation methods complicates reliable flexural strength testing across laboratories.

Purpose of the Study:

• To investigate the influence of processing method, surface treatment, and testing technique on the flexural strength of zirconia.
• To determine optimal specimen preparation for maximizing zirconia flexural strength and reliability.

Main Methods:

• Zirconia specimens (VITA YZ HT, n=270) were prepared via CAD/CAM or conventional milling.
• Surface treatments included machined, ground, and polished finishes.
• Flexural strength was assessed using three-point bending (non-chamfered/chamfered) and biaxial flexural strength tests, analyzed with Weibull statistics.

Main Results:

• Mean flexural strength varied from 612 MPa (conventional, machined, 3-point bending non-chamfered) to 1143 MPa (CAD/CAM, polished, biaxial).
• CAD/CAM processing combined with polishing demonstrated the highest reliability and strength.
• The biaxial flexural strength test yielded higher values due to reduced stress concentration.

Conclusions:

• CAD/CAM processing and polishing are recommended for superior zirconia flexural strength and reliability in dental applications.
• Polishing effectively minimizes surface microcracks, enhancing material strength.
• Testing methodology significantly influences measured flexural strength values.