ABSTRACT: 1808

Microhardness of dual-cured composites cured by LED

J.-W. PARK¹, S.-J. SHIN¹, D.G. SEO¹, and J.Y. LEE², ¹Yonsei University, Seoul, South Korea, ²National Health Insurance Medical Center, Ilsan Hospital, Goyang, South Korea

Objective: In the previous study, we tested the dual-cured composite core materials cured by halogen light and it showed that the polymerization of the bottom of bulk-cured composites were incomplete when the thickness was over 4mm. In this study, we used the high power LED for polymerization and measured the microhardness at top and bottom surface.

Materials and methods: Luxacore(DMG), Multicore Flow(Ivoclar/Vivadent) and Paracore(Coltene/Whaledent) were packed into 2, 4, 6, 8mm thickness molds and cured with LED unit(Mini LED, 1100mW/cm²). Each group was cured 20, 40, 60, 80sec respectively, and self-cure group of 8mm thickness was added. The specimens were stored in distilled water at 37℃ for 24 hours. The Knoop microhardness of top and bottom surfaces were measured and the bottom/top ratio was calculated (n=3). The results were analyzed using one-way ANOVA and Tukey's test.

Results: Paracore showed no significant difference. Luxacore and Multicore self-cure groups showed lower hardness than light-cure groups at top surface. Microhardness of bottom of light-cure groups decreased till 6mm and increase at 8mm. However the bottom/top ratio was not significantly different.

Luxacore

Multicore Flow

Paracore

Group

Top

Bottom

Ratio

Group

Top

Bottom

Ratio

Group

Top

Bottom

Ratio

2
4
6
8
8self

47.3(2.94)^a
46.2(2.21)^a
46.4(1.46)^a
46.3(1.40)^a
26.5(0.14)^b

41.9(1.30)^a
29.2(2.03)^b
18.0(1.37)^d
21.2(2.61)^cd
25.6(0.47)^bc

0.89(0.05)^a
0.63(0.07)^b
0.39(0.02)^c
0.46(0.04)^c
0.96(0.01)^a

2
4
6
8
8Self

40.2(2.51)^a
39.0(1.53)^a
40.7(2.24)^a
39.3(3.77)^a
25.7(0.55)^b

36.6(2.62)^a
27.6(0.75)^b
17.9(1.04)^c
20.7(1.12)^c
24.7(0.98)^b

0.91(0.04)^a
0.71(0.04)^b
0.44(0.05)^c
0.53(0.02)^c
0.96(0.04)^a

2
4
6
8
8self

32.7(1.58)
36.5(2.74)
33.5(1.96)
35.6(3.94)
30.0(4.51)

26.8(1.27)
28.5(3.08)
21.7(2.85)
26.3(3.61)
30.8(5.29)

0.82(0.01)
0.78(0.08)
0.65(0.11)
0.74(0.02)
1.05(0.29)

Conclusion: Following the results of this experiment, deep portion of dual-cure composite is not sufficient and it showed lower value than self-cure groups when cured with LED unit. Thus incremental filling rather than bulk filling is recommended.

Seq #188 - Polymerization of Resin-based Materials
2:00 PM-3:15 PM, Friday, July 4, 2008
Metro Toronto Convention Centre Exhibit Hall D-E

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