J Korean Acad Conserv Dent.  2011 Jul;36(4):324-335. 10.5395/JKACD.2011.36.4.324.

Effects of the color components of light-cured composite resin before and after polymerization on degree of conversion and flexural strength

• Yoo JA
• Cho BH

• KMID: 1986695
• DOI: http://doi.org/10.5395/JKACD.2011.36.4.324

Abstract

OBJECTIVES
This study investigated the effects of the color components of light-cured composite resin before and after polymerization on degree of conversion (DC) and biaxial flexural strength (FS).
MATERIALS AND METHODS
Four enamel shades (A1, A2, A3, A4) and two dentin shades (A2O, A3O) of Premisa (Kerr Co.) and Denfil (Vericom Co.) were evaluated on their CIE L*, a*, b* color components using the spectrophotometer before curing, after curing and at 7 day. The DC of same specimens were measured with Near-infrared spectrometer (Nexus, Thermo Nicolet Co.) at 2 hr after cure and at 7 day. Finally, the FS was obtained after all the other measurements were completed at 7 day. The correlations between each color component and DC and FS were evaluated.
RESULTS
The light-curing of composite resin resulted in color changes of Premisa in red-blue direction and Denfil in green-blue direction. The DC and FS were affected by product, time and shade (3-way ANOVA, p < 0.05) and product and shade (2-way ANOVA, p < 0.05), respectively. Premisa only showed a significant correlation between the DC and CIE a* component - before and after polymerization (Pearson product moment correlation, p < 0.05). The FS of Premisa showed significant negative correlations with CIE a* and CIE b* components.
CONCLUSIONS
The DC and FS of the light-curing composite resin were affected by the color components of the material before and after polymerization.

Keyword

Biaxial flexural strength; CIE Lab*; Degree of conversion; Light-cured composite resin; Shade

MeSH Terms

Dental Enamel
Dentin
Polymerization
Polymers
Polymers

Figure

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  Figure 1 Measurement assembly for measuring biaxial flexural strength. The assembly had a specimen support and a loading steel rod, which was used in a universal testing machine. For the support of the test specimen, three steel balls with a diameter of 3.0 mm, positioned 120° apart on a support circle with a diameter of 10 mm, was provided. The sample was placed concentrically on these supports and the load was applied with a flat punch with a diameter of 1.5 mm at the center of the specimen.

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  Figure 2 Changes in CIE L* values of each shade of (a) Premisa and (b) Denfil. Both products showed a relatively great decrease in the value (lightness) of each shade after curing. However, until 7 days, the values were a little increased.

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  Figure 3 Changes in CIE a* values of each shade of Premisa and Denfil. (a) The products of Denfil showed a relatively great decrease in the redness of each shade after curing. However, until 7 days, the values were a little increased. (b) The products of Premisa showed a gradual increase in the redness of each shade after curing.

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  Figure 4 Changes in CIE b* values of each shade of (a) Denfil and (b) Premisa. Both products showed a gradual decrease in the yellowness of each shade after curing.

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  Figure 5 Changes in degree of conversion (%) of each shade of (a) Denfil and (b) Premisa. Both products showed a gradual increase in the degree of conversion of each shade from 2 hours after curing to 7 days.

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