Microstructural development during crystallization firing of a dental-grade nanostructured lithia-zirconia glass-ceramic

The microstructural development during crystallization firing of a commercially-available dental-grade nanostructured lithia-zirconia glass-ceramic (Vita Suprinity (R) PC) was unraveled using a wide battery of ex-situ and insitu characterization techniques. It was found that the milling blocks are slightly crystallized glass-ceramics, with a complex chemical composition and consisting of partially de-polymerized glass plus lithium silicate (Li2SiO3) nanocrystals. It was also found that during crystallization firing the glassy matrix first reacts with part of the Li2SiO3 to form lithium disilicate (Li2Si2O5) at -810-820 degrees C, and then lithium orthophosphate (Li3PO4) precipitates from the glass. This results in glass-ceramics with abundant nanocrystals embedded in a sparse zirconosilicate glass matrix (containing many other cations subsumed) that, due to its high viscosity, inhibited crystal growth. Therefore, these dental glass-ceramics are not reinforced with zirconia (ZrO2) crystals unless over-fired above -890 degrees C and at the expense of its singular nanostructure. Finally, this study opens doors for optimizing the clinical performance of these dental glass-ceramics via microstructural tailoring.

Automated summary

This study elucidates the microstructural development of a commercially-available dental-grade nanostructured lithia-zirconia glass-ceramic during crystallization firing, revealing a complex chemical composition and crystal phase transition process. These dental glass-ceramics can form abundant nanostructures at appropriate temperatures, but caution should be taken to avoid over-firing that may damage their unique nanostructure. Therefore, optimizing the clinical performance of these glass-ceramics can be achieved through microstructural design.