Experimental bilayer zirconia systems after aging: Mechanical, optical, and microstructural characterization

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Ceramics

Background:

• Zirconia-based ceramics are widely used in dentistry due to their mechanical properties.
• Investigating bilayer zirconia structures offers potential for improved material performance.
• Understanding the effects of hydrothermal aging is crucial for long-term clinical success.

Purpose of the Study:

• To characterize experimental zirconia bilayer materials.
• To compare their properties to monolithic zirconia controls.
• To evaluate the impact of hydrothermal aging on material performance.

Main Methods:

• Fabrication of two bilayer zirconia materials (3Y-TZP+5Y-PSZ and 4Y-PSZ+5Y-PSZ) and monolithic controls.
• Sintering at 1550°C followed by hydrothermal aging (134°C, 20h).
• Characterization using SEM, XRD, Raman spectroscopy, reflectance, and biaxial flexural strength testing (ISO 6872).

Main Results:

• Degradation and monoclinic phase observed in aged 3Y-TZP and 4Y-PSZ.
• Bilayer materials exhibited intermediate strength compared to controls.
• Hydrothermal aging increased strength in most groups, with variations observed.

Conclusions:

• Experimental bilayer zirconia showed lower mechanical properties than monolithic controls.
• Both bilayer and monolithic materials met ISO 6872 standards for various dental prostheses.
• Specific materials, including monolithic 3Y-TZP, 4Y-PSZ, and bilayer 3Y+5Y, met higher strength requirements for longer fixed dental prostheses.