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KMID : 0362220100370010029
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Journal of The Korean Research Society for Dental Materials
2010 Volume.37 No. 1 p.29 ~ p.37
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Effect of Thermal Cycling on Elastic Modulus and Hardness of Dental Composites by the Nano-Indentation Technique
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Lee Gye-Young
Oh Young-Taek
Kim Tae-Gun
Yu Mi-Kyung
Lee Kwang-Won
Kim Kyoung-Sun
Lee Min-Ho
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Abstract
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The purpose of this study was to investigate the effect of thermal cycling on the elastic modulus and hardness of dental composites using the nano-indentation technique. Five materials from the different manufacturer were selected for this study, which were micro-hybrid (Esthet-X flow), hybrid (Spectrum TPH), microfilled (Filtex Z250), flowable (Unifil Flow), and compomer (F2000). All specimens were polished sequentially from #600 to #1200 emery paper and buffer clothes with 0.3 μm alumina paste. The thermal cycled specimen was immersed in distilled water and treated in a thermal cycler for 3000 cycles at temperatures ranging from 5℃ to 55℃ with a 10-second dwell time. Nano-indentation was used to determine the hardness and elastic modulus for specimens before and after thermal cycling. Also, the specimens were analyzed with surface roughness tester and scanning electron microscope (SEM). Data were analyzed using independent t-test (α=0.05). The result showed that surface roughness of all specimens were significantly decreased after thermal cycling (P<0.05) and for the roughness change, Spectrum TPH (SP) was 80%, F2000(F2) was 42%. F2000 (F2) with compomer showed the highest and Unifill flow (UN) with flowable the lowest values of hardness and elastic modulus. After thermal cycling, the hardness and elastic modulus of Esthet-X flow (ES)와 Spectrum TPH (SP) were significantly decreased, Unifil Flow (UN) significantly increased (P<0.05) and there was no significant difference for Filtex Z250 and F2000 (F2) (P>0.05). Microstructure of specimens after thermal cycling was smoother than before thermal cycling and F2000 appeared micro cracks on the surface after thermal cycling.
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KEYWORD
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Restorative materials, Nano indentation, Hardness, Elastic modulus, Surface roughness
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