微波烧结和常规烧结对牙科用氧化锆半透性影响的对比研究

Translucency of dental zirconia ceramics sintered in conventional and microwave ovens

目的研究微波烧结对氧化锆半透性的影响并与常规烧结对比,分析半透性与显微结构的相关性。方法选取Lava和Zenostar两种品牌氧化锆试件各10个,每组5个试件,常规烧结组温度分别为1 500℃和1 490℃,保温2 h;微波烧结组均以15℃·min^(-1)升温至1 420℃,保温30 min。用Shade Eye NCC电脑比色仪测量各试件在白背景下和黑背景下的明度的分级(L*)、红到绿两色相极的变化(a*)、黄到蓝两色相极的变化(b*)值,并计算半透性参数(TP),阿基米德排水法测量各试件的密度,扫描电镜(SEM)观察各试件的显微结构。结果与常规烧结相比,微波烧结Lava和Zenostar氧化锆晶粒尺寸小且均匀一致,密度和TP值虽较高,但差异并无统计学意义(P>0.05)。Lava氧化锆的TP值大于Zenostar氧化锆(P<0.001)。结论微波烧结氧化锆瓷的半透性能与常规烧结相当。

Objective To evaluate the effect of microwave sintering on the translucency of zirconia and to compare these effect with those of conventional sintering. The relationship between the microstructure of specimens and translucency was investigated. Methods A total of 10 disc-shaped specimens were fabricated from 2 commercial brands of zirconia, namely, Zenostar and Lava. Each group included 5 discs. Conventional sintering was performed according to the manufacturers＇ specifications. The maximum temperature for Zenostar was 1 490 ℃, whereas that for Lava was 1 500 ℃. The dwelling time was 2 h. The sintering temperature for microwave sintering was 1 420 ℃, heating rate was 15 ℃·min-1, and dwelling time was 30 min. After sintering, the translucency parameter（TP） of the specimens were measured with Shade Eye NCC. The sintered density of the specimens was determined by Archimedes＇ method. The grain size and microstructure of the specimens were investigated by scanning electron microscopy. Results Density and translucency slightly increased by microwave sintering, but no significant difference was found between microwave and conventional sintering（P〉0.05）. Small and uniform microstructure were obtained from microwave sintering. The mean TP of Lava was significantly higher than that of Zenostar（P〈0.001）. Conclusion The translucency of zirconia sintered by microwave sintering is similar to that of the zirconia sintered by conventional sintering.