Abstract:

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-gritgrinding 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.

Key words: Surface roughness, Dental amalgam, Fracture resistance