J Korean Acad Conserv Dent JKACD Journal of Korean Academy of Conservative Dentistry 1225-0864 2093-8179 The Korean Academy of Conservative Dentistry 10.5395/JKACD.2004.29.1.058 Original Article Effect of each light curing units on the microhardness and microleakage of composite resin Jung Eu-Jin Lee Hee-Joo Hur Bock Department of Conservative dentistry, College of Dentistry, Pusan National University, Korea. Corresponding author: Eu-Jin Jung. Department of Conservative Dentistry, Collage of Dentisry, Pusan National University, 1-10, Ami-dong, Seo-gu, Pusan, 602-739, Korea. Tel: 051)240-7454, carrot31@freechal.com 01 2004 31 01 2004 29 1 58 65 Copyright © 2004 Korean Academy of Conservative Dentistry 2004

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The objectives of this study was to evaluate current visible light curing units regarding microhardness and microleakage. Fourty samples of composite resin(Z-250, 3M) were cured by different light curing units(Flipo, LOKKI; Credi II, 3M; XL 3000, 3M; Optilux 500,Demetron) in acrylic blocks. Microhardness was measured using a calibrated Vickers indenter on both top and bottom surfaces after 24 hours of storage in air at room temperature. Class V cavities were prepared on buccal and lingual surfaces of fourty extracted human molars. Each margin was on enamel and dentin/cementum. Composite resin(Z-250, 3M) was filled in cavities and cured by four different light curing units(Flipo, LOKKI; Credi II, 3M; XL 3000, 3M; Optilux 500, Demetron).

The results of this syudy were as follows:

Microhardness

1. Flipo showed low microhardness compared to Optilux 500, Credi II significantly in upper surface. Flipo didn't show a significant difference compared to XL 3000.

2. The microhardness resulting from curing with Flipo was lower than that of others on lower surfaces.

Microleakage

1. Dentin margin showed significantly high dye penetration rate than enamel margin in all groups(p<0.05).

2. No significant differences were found on both enamel and dentin margin regarding curing units.

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Diagram of acrylic plastic mold showing light tip in position over resin sample.

Microhardness of upper and lower surface

The ratings of the dye penetration at enamel and dentin margin

Light curing mode

The ratings of the dye penetration

Microhardness of upper and lower surface

Microhardness of upper and lower surface cured by each light curing unit

Statistical difference of upper and lower surface

*Different Tukey letters denote statistically different groups

The ratings of the dye penetration at enamel and dentin margin

*Same Tukey letters denote statistically same groups