Can heat-pressed feldspathic ceramic be submitted to multiple heat-pressing?

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Ceramics

Background:

• Dental ceramics are crucial for prosthetics, but their reprocessing for sustainability is under investigation.
• Understanding the effects of multiple heat-pressing cycles on ceramic properties is essential for clinical application and material longevity.

Purpose of the Study:

• To evaluate the influence of multiple heat-pressing cycles and mechanical cycling on the flexural strength, hardness, and microstructure of Vita PM9 dental ceramic.
• To determine the feasibility of recycling this dental ceramic without compromising its mechanical integrity.

Main Methods:

• Ninety Vita PM9 ceramic specimens were subjected to 1, 2, or 3 heat-pressing cycles, with half also undergoing mechanical cycling.
• Flexural strength was assessed using 3-point bending tests, and Vickers hardness was measured.
• Microstructure and phase characterization were performed using scanning electron microscopy and X-ray diffraction, respectively.

Main Results:

• Neither the number of pressings nor mechanical cycling significantly affected the overall flexural strength, though Weibull analysis indicated differences in strength distribution.
• A significant interaction between the number of pressings and mechanical cycling was observed for hardness, with hardness generally decreasing with more pressings.
• Increased firing cycles led to a reduction in observed microstructural defects.

Conclusions:

• Reprocessing Vita PM9 dental ceramic through multiple heat-pressing cycles appears to be a viable option without significant detrimental effects on flexural strength.
• While hardness may decrease with reprocessing, the observed microstructural improvements suggest potential benefits for material longevity and recyclability.