Background: Effective polymerization of the composite resin is essential to obtain long term clinical success and has a great importance obtaining improved mechanical properties. The purpose of this study was to measu...Background: Effective polymerization of the composite resin is essential to obtain long term clinical success and has a great importance obtaining improved mechanical properties. The purpose of this study was to measure the effect of the light intensity of LED and QTH curing devices in relation to the light distances, on the hardness (KHN) of two light cure nano-resin composite. Material and Methods: The top and bottom surfaces of the two nanofill composite specimens were evaluated. Two LED and two QTH light curing devices were used at nine different distances. Light intensity was measured with two radiometers placed at these same distances from the curing tip. 360 pvc dies were prepared with circular cavity 3 mm in diameter and 2 mm thick. The tested materials were placed in each cavity. The different light curing distances were standardized by adding pvc spacers dies at different height matching the different distances. Top and bottom surface microhardness were evaluated with a Micro Hardness Tester in knoop hardness numbers (Kg/mm2). Data were statistically analyzed using: Three-way ANOVA, Tukey and Pearsons test. Results: It was revealed that there was a statistically significant difference in microhardness between the composites (p < 0.001), between the nine distances (p < 0.001) and between the four light curing devices (p < 0.001). Increasing the distance of the light source from composite resin, the light intensity and the microhardness values at the top and bottom surface decrease. LED light curing devices produced a greater microhardness results at the bottom surface of the specimens. The Filtek Ultimate nanocomposite (3 m) showed highest microhardness values on the top and bottom surfaces, polymerized with all four curing devices and all nine distances compared to Empress Direct nano composite (Ivoclar vivadent). Clinical significant: Even with high power LED curing light, the distance between the tip of the light source and the restoration surface should be as close as possible. In this study, Filtek Ultimate showed better results (highest microhardness values) than Empress Direct.展开更多
以智能、环保为主题的新型电力系统是中国电力领域发展的主要方向,因此对绝缘材料的各方面性能提出了更高的要求。文中基于高韧性环氧大豆油基光敏树脂,在光固化树脂中添加60 wt%的环氧树脂,采用3D打印光固化和热固化的两步固化方式,制...以智能、环保为主题的新型电力系统是中国电力领域发展的主要方向,因此对绝缘材料的各方面性能提出了更高的要求。文中基于高韧性环氧大豆油基光敏树脂,在光固化树脂中添加60 wt%的环氧树脂,采用3D打印光固化和热固化的两步固化方式,制备得到力学和电学性能优异的双固化树脂,并对其进行回收重塑得到回收后的双固化树脂。分别对树脂的拉伸强度、弯曲强度、介电性能、体积电阻率进行测试,研究表明,制备的双固化树脂相比于纯光固化树脂,具有优异的力学性能和绝缘性能,回收后树脂的力学强度是新制树脂的80%。对树脂进行沿面闪络实验,测得双固化树脂的闪络电压达到26.3 k V,采用威布尔分布图看出闪络电压还具有较小的分散性。回收的树脂沿面闪络电压略有降低,但仍然高于纯光固化树脂。分析了表面电荷特性对直流沿面闪络电压的影响。展开更多
文摘Background: Effective polymerization of the composite resin is essential to obtain long term clinical success and has a great importance obtaining improved mechanical properties. The purpose of this study was to measure the effect of the light intensity of LED and QTH curing devices in relation to the light distances, on the hardness (KHN) of two light cure nano-resin composite. Material and Methods: The top and bottom surfaces of the two nanofill composite specimens were evaluated. Two LED and two QTH light curing devices were used at nine different distances. Light intensity was measured with two radiometers placed at these same distances from the curing tip. 360 pvc dies were prepared with circular cavity 3 mm in diameter and 2 mm thick. The tested materials were placed in each cavity. The different light curing distances were standardized by adding pvc spacers dies at different height matching the different distances. Top and bottom surface microhardness were evaluated with a Micro Hardness Tester in knoop hardness numbers (Kg/mm2). Data were statistically analyzed using: Three-way ANOVA, Tukey and Pearsons test. Results: It was revealed that there was a statistically significant difference in microhardness between the composites (p < 0.001), between the nine distances (p < 0.001) and between the four light curing devices (p < 0.001). Increasing the distance of the light source from composite resin, the light intensity and the microhardness values at the top and bottom surface decrease. LED light curing devices produced a greater microhardness results at the bottom surface of the specimens. The Filtek Ultimate nanocomposite (3 m) showed highest microhardness values on the top and bottom surfaces, polymerized with all four curing devices and all nine distances compared to Empress Direct nano composite (Ivoclar vivadent). Clinical significant: Even with high power LED curing light, the distance between the tip of the light source and the restoration surface should be as close as possible. In this study, Filtek Ultimate showed better results (highest microhardness values) than Empress Direct.
文摘以智能、环保为主题的新型电力系统是中国电力领域发展的主要方向,因此对绝缘材料的各方面性能提出了更高的要求。文中基于高韧性环氧大豆油基光敏树脂,在光固化树脂中添加60 wt%的环氧树脂,采用3D打印光固化和热固化的两步固化方式,制备得到力学和电学性能优异的双固化树脂,并对其进行回收重塑得到回收后的双固化树脂。分别对树脂的拉伸强度、弯曲强度、介电性能、体积电阻率进行测试,研究表明,制备的双固化树脂相比于纯光固化树脂,具有优异的力学性能和绝缘性能,回收后树脂的力学强度是新制树脂的80%。对树脂进行沿面闪络实验,测得双固化树脂的闪络电压达到26.3 k V,采用威布尔分布图看出闪络电压还具有较小的分散性。回收的树脂沿面闪络电压略有降低,但仍然高于纯光固化树脂。分析了表面电荷特性对直流沿面闪络电压的影响。
