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KMID : 0988420020140040370
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Journal of Dental Science (C.N.U.)
2002 Volume.14 No. 4 p.370 ~ p.382
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Comparison of Degree of Conversion in Light-cured Composite Cured by Halogen and Plasma Xenon Arc Lamp Curing Unit
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Abstract
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Light-cured composite resin that is widely employed in esthetic restorative dentistry shows different degree of polymerization according to chemical composition of resin product, intensity and exposure time of curing unit, method of filling etc. Light cured composite resin is required of multi-layered curing with proper thickness to minimize the problems like insufficient polymerization or polymerization shrinkage. However, it brings the increment of total chair time.
Recently. new light curing unit utilizing the plasma xenon arc lamp is introduced. This curing unit is operated at relatively high intensity so shortening the curing time signifiantly.
The aim of this experiment was to estimate curing capability of plasma xenon arc lamp curing unit compared to traditional halogen lamp curing unit. Resin specimens were prepared in aluminum mold with diameter of 7mm and thickness of 1mm, 2mm, 3mm. Degree of polymerization was evaluated by Raman spectroscopy after irradiation of specimens with halogen lamp curing unit(Optilux 15O, Demetron, USA) for 20s, 40s. 60s and plasma xenon arc lamp curing unit(flipo, Lokki. Francr) for 2s, 3s, 6s.
The following results are obtained.
1. The light intensity was 472mW/cm^2 in halogen lamp curing unit (Optilux 150. Demetron, USA) and 1945mW/cm^2 in plasma xenon arc lamp curing unit (flipo, Lokki, France) In both curing units, the range of wavelength was between 370 and 520nm and showed peak intensity at about 470nm.
2. The degree of conversion at exposured surface was increased significantly with increment of exposure time in both curing unit(p<0.01). Overall degree of conversion was higher in halogen lamp curing unit when compared to plasma xenon arc lamp curing unit, but there was no significant difference.
3. In both curing unit, the degree of conversion at bottom surface was decreased significantly according to an increase in thickness(p<0.05). In thickness of 3mm cured with plasma xenon arc lamp curing unit, the degree of conversion showed decreased values significantly compared to thickness of 1,2mm(p<0.01).
4. In halogen lamp curing unit, the degree of conversion increased in all thickness as exposure time increased, but there was no significant difference in 1.2mm thickness. Plasma xenon arc lamp curing unit showed significantly increased degree of conversion as increase of exposure time in all thickness (p<0.01).
From the above results, it was concluded that strong light intensity of plasma xenon arc lamp
curing unit did not compensate for short exposure time completely. So. Multi-layered curing within 2mm thickness and additional exposure time Is recommanded when light-cured cpmposite resin is polymerized with plasma xenon arc lamp curing unit.
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