表面粗糙度对牙科银汞合金抗折力的影响

目的比较不同表面粗糙度的牙科银汞合金试件的断裂载荷，探讨试件表面状况对脆性牙科材料抗折力的影响。方法制作直径10mm、厚2mm的圆盘形银汞试件48个．随机分成4组，其中3组分别以220、400、1200号SiC砂纸双面磨平．另一组不经打磨．表面保持试件制作完毕后的自然状态。每组随机抽取5个试件，置于粗糙度测试仪上测量表面粗糙度。试件于（23±1）。C空气中保存7d后置于30％玻璃纤维加强尼龙6．6基底上以20mm直径不锈钢球加载进行赫兹压痕试验，记录初始断裂载荷值并进行统计分析。结果未经打磨、220号、400号、1200号SiC砂纸打磨的试件的表面粗糙度平均值分别为1．77、1．99、1．28、0．66μm，断裂载荷值分别为（656．1±44．1）、（644．9±57．9）、（678.3±40．4）、（721．1±60．1）N。随着粗糙度的降低，初始断裂载荷值逐渐增加，1200号砂纸打磨组与未经打磨组和220号砂纸打磨组之间差异有统计学意义（P〈0．05）。结论脆性材料试件的表面粗糙度对其抗折能力有一定影响．

Effect of surface roughness on the fracture resistance of amalgam

Objective To compare the failure load of amalgam with various surface roughness and explore the effect of surface condition on the fracture resistance of brittle dental materials. Methods Forty eight amalgam discs of 10 mm diameter and 2 mm thickness were prepared. Specimens were randomely divided into 4 groups. Three groups were grinded with SiC sandpaper of 220, 400 and 1220 grit respectively and the fourth group remained nature without grinding. Roughness of the specimens of each group was tested with a roughness tester. After stored in （23 ± 1 ） ℃ dry air for 7 days, specimens were tested on top of glass-reinforced polyamide-nylon 6,6 substrates by a univeral testing machine, loading centrally with a 20 mm diameter ball. Loads at the first crack were recorded and analyzed. Results The mean roughtnesses of the specimens of the nature state without grinding, 220-grit-grinding, 400-grit-grinding and 1200-grit-grinding were 1.77, 1.99, 1.28 and 0.66 μm respectively. Failure loads were measured to be （656.1 ± 44.1 ）, （644.9 ± 57.9）, （678.3 ± 40.4）, （721.1 ± 60.1） N respectively. The failure load increased with the decrease of roughness, significant difference was found among 1200-grit-grinding group, 220-grit-grinding group and without grinding group （P 〈 0.05）. Conclusion Surface roughness of brittle materials has certain effect on their fracture resistance.