Flexural Strength of Different Yttrium Oxide– Containing Monochrome and Multilayer Partially Stabilized Zirconia at Various Sintering Rates.

This article investigates the effects of varying sintering rates on the flexural strength (σ) of 3, 4, and 5 mol% yttria-containing monochrome (Mo) and multilayer (Mu) zirconia used in dental restorations. The study found that flexural strength was significantly influenced by yttria content (3Y > 4Y > 5Y), shade pattern (Mu > Mo), and sintering rate (regular and fast sintering rates yielded higher strength than speed sintering), though varying sintering rates within each zirconia type did not significantly affect strength. Microstructural analysis showed larger grain sizes and higher cubic phase content in 5Y zirconia, while 3Y zirconia had more tetragonal phase, which is associated with higher strength. The findings suggest that regular and fast sintering rates are preferable for producing high-strength restorations, while speed sintering can still yield clinically acceptable strength, offering a time- and cost-efficient option for chairside fabrication.