Influence of Final sintering temperature on flexural strength and microstructures of Nano zirconia dental implant materials

Objectives investigate the effect of final sintering temperature on the mechanical and microstructural properties of Nano zirconia ceramic used for fabrication of dental implant.
Material and method forty eight bar of zirconia test pieces were prepared from uniaxial compaction of Nano zirconia powder in die mold by laboratory manual hydraulic press at 120MPa.The sintered specimens were randomly divided into four groups according to sintering temperature (n=12 per group) . The sintering procedure was performed at 3 hours holding time, the heating and cooling rate was 10℃ /mim ,and four final sintering temperatures were (1450,1500, 1550, and 1600) ℃ .The flexural strength was measured by three point bending test through universal testing machine at cross rate 1mm/min according to ISO18754:2015. The crystallographic analysis was investigation by x-ray diffractometer, microstructure and grain size were investigation by field emission scanning electron microscope. Data were analyzed by one way ANOVA with (p<0.05).
Results the highest flexural strength was observed in group of nan zirconia sintered at 1550℃ (891.3±2.62679) MPa, while the lowest for group sintered at1450 ℃(.793±2.9829) MPa .XRD data and the FESEM micrographs reveal the greatest crystallite size (33.6)nm , and grain size (0.85)μm were for samples sintered at 1600℃.
Conclusion
The highest flexural strength was for Nano zirconia sintered at 1550℃.The grain size and crystallite size were increased with increased sintering temperatures.