Comparison The Translucency Of Dental Zirconia Ceramics Sintered In Conventional And Microwave Ovens

Objective:The purpose of this study was to evaluate the effects of different sintering temperature of microwave sintering on the density and translucent of zirconia made with two different materials and compared with conventional sintering. And provide theoretical basis for the clinical application of microwave sintering in the future.Maternal and methods:Forty disc-shaped specimens,10 mm in diameter and o.5±0.05 mm in thickness were fabricated from of two commercial brands of zirconia(Zenostar and Lava).these specimens were sintered in a microwave oven and were divided into three groups based on different sintering temperatures 1350,1420 and 1490(Zenostar),1500(Lava)respectively, dwelling time was 30 minutes. The conventional sintering followed the manufacturers’ specifications. The maximum temperature of Zenostar was1490 ℃,dwelling time was 2 hour. The maximum temperature of Lava was1500 ℃,dwelling time was 2 hour. Each group included five discs. Microwave sintering was completed according to the specifications of the microwave oven manufacturer.After sintering, TP of the specimens under the different sintering temperature were measured with Shade Eye NCC. The sintered density of the specimens was determined by Arci-medes’ method. Grains size and microstructure of Specimens were investigated via scanning electron microscopy. The dates were statistically analyzed.Results:1. Concerning density and translucency, two-way ANOVA revealed significant differences between groups with different sintering temperature and brands(<0.001).Tukey’s tests revealed that there was a significant decrease in TP when comparing the MS1 to the MS2 and MS3. However, there was no statistically significant difference between MS2 and MS3.For density of Zenostar, there was a significant decrease in density when comparing the MS1 to the MS2 and MS3, However, there was no statistically significant difference MS1 to the MS2 and MS3 for Lava. SEM showedporosity decreased, density increased, grain grew evenly and grain boundary arrangement regular as the sintering temperature increased. However, as the temperature increased a little, grain size grew unevenly, the TP decreased.2. When the temperature was 1420 ℃,the values of density and translucent increased a little by microwave sintering, but there was no sin significant differences between microwave sintering and conventional sintering.Concluson:1. Microwave sintering temperature affected the density and TP of Zenostar and Lava. With the limitations of this study, the best sintering temperature was 1420℃.2. Compared with conventional sintering, when temperature was 1420℃,the use of microwaves provides several advantages, such as, high TP,lower heating temperatures and greatly reducing the total thermal cycle length.