Effect of Various Nano Zro contents and sintering temperature on fracture toughness and hardness of In-ceram zirconia

Abstract

Mechanical properties is one of the most important weaknesses of full Ceramic restorations and it caused limitation of their application in posterior areas in the mouth. With the introduction of zirconia, mechanical properties of full Ceramic restoration improved to some extent. The aim of this study was to evaluate the effect of added variable weight percentage of nano zirconia in In-Ceram Zirconia to improve mechanical properties of it. Methods: In this study the weight percentage of nano zirconia (,,, & % ) and sintering temperature of it (,, & C) have been selected as a variable parameters in levels. Experimental design (general factorial method) has been used for running experiment and at least experiments by repetitions have been designed. DX software was used for all statistical analysis. The total number of samples were ones. The zirconia nano powder with different weight percentage included , , , % have been mixed by In-Ceram Zirconia powder and the samples were prepared in standard size and then was sintered in various temperature according the company procedure. Hardness were measured with Vickers microhardness method. The optical microscope has been used for determination the amount of hardness and crack length measurement (for determination of fracture toughness). SEM has been used to measure the surface characteristics of particles. All statistical analysis such as ANOVA, mean square and comparing results have been done by DX software. Results: Results show that addition of the nano zirconia improves fracture toughness and hardness of samples to some extent, but by increasing the percentage of nano zirconia loss of properties were observed. Additionally increasing of sintering temperatures was lead to increasing of hardness and reduction of fracture toughness. Conclusion: Addition of the nano zirconia powder up to % and thermal sintering in C leads to increasing of fracture toughness and improvement the properties of samples.