RESUMEN
The purpose of this in vitro study was to evaluate the effect of speed sintering on flexural strength, density, and linear shrinkage of monolithic zirconia. Four hundred Ø18.7×1.7-mm presintered zirconia specimens were divided into 8 groups (n=50) based on the sintering times (speed (60, 90, and 120 min) or normal (540 min)) and temperatures (1400, 1450, 1500, and 1550 ℃). The mechanical properties (Vickers hardness, biaxial flexural strength, and fracture toughness) and physical properties (linear shrinkage, density, and porosity) were examined. The crystallite size of zirconia was calculated using scherer’s formula. The mechanical properties (biaxial flexural strength, Vickers hardness, and fracture toughness) of all specimens increased with increasing sintering times and temperatures. The biaxial flexural strength of the SS groups sintered 1500 ℃ and 1550 ℃ with 120 min showed similar value compared with NS groups. The SS 120 and NS groups showed similar the linear shrinkage percentages at all temperatures. The porosity decreased with increasing sintering times and temperatures in all specimens.The sintered and relative density and the average crystallite size increased with increasing sintering times and temperatures in all specimens. The average crystallite size ranged from 70.1 nm to 129.8 nm. XRD analysis showed the presence of a tetragonal metastable phase in all groups before and after sintering. The biaxial flexural strength values under speed sintering (1500 ℃ and 1550 ℃, 120 min) were similar to those of normal sintering groups.