The L* coordinate is a measure of the lightness-darkness of the s

The L* coordinate is a measure of the lightness-darkness of the specimen. The greater the L* is, the lighter the specimen. The a* coordinate sellckchem is a measure along the red-green axis. A positive a* relates to the amount of redness, and a negative a* relates to greenness of a specimen. The b* coordinate is a measure along the yellow-blue axis, that is a positive b* relates to the amount of yellowness; a negative b* relates to the amount of blueness of the specimen. ��L*, ��a* and ��b* are the differences in the CIE color-space parameters of the 2 colors.23 Threshold color difference levels based on instrumental color measurements that can be visually perceivable or clinically acceptable have been discussed. However, the clinically acceptable value for color difference in restorative materials is assumed to be ��E* 3.

3.24 The aim of this in vitro study was to investigate the amount of change in color and color parameters of composite resin material (Filtek P60, 3M ESPE) polymerized by five different polymerization methods. The null hypothesis of the present study were that (1) the polymerization methods don��t affect the color parameters of composite resin material, (2) there is no color difference between unpolymerized and polymerized composite resin regarding the polymerization methods. MATERIALS AND METHODS The composite resin used in this study was Filtek P60 (color A3; 3M ESPE, St. Paul, U.S.A.) packable light-cured composite. A 6mm diameter hole was made in a 2mm high Teflon plate and filled with composite resin.

After inserting the composite resin material into the Teflon plate, a strip was laid on the top of the specimens and the color of the composite specimens before polymerization was measured on stripped surfaces. Five groups were considered for color change (n=10) (Table 1). Table 1 Prortocols of polymerization in this study. Group I: Polymerization with inlay oven (Tescera ATL, Bisco, USA) for 15 minutes. Group II: Conventional polymerization with HQTH unit (High Quartz Tungsten Halogen Blue Luxer, Monitex, Taipei, Taiwan) at 740 mW/cm2 for 30 seconds and post-polymerized in an autoclave (Europa B xp, Tecno-gaz, Italy) at 30 PSI pressure, 134��C heat for 17 minutes. Group III: Conventional polymerization with LED unit (Light-Emitting Diode Demi, Kerr, Orange, USA) at 1100 mW/cm2 for 20 seconds and post-polymerized in an autoclave (Europa B xp, Tecno-gaz, Italy) at 30 PSI pressure, 134��C heat for 17 minutes.

Group IV: Conventional polymerization only with HQTH unit (Blue Luxer, AV-951 Monitex, Taipei, Taiwan) at 740 mW/cm2 for 30 seconds. Group V: Conventional polymerization only with LED unit (Demi, Kerr, Orange, USA) at 1100mW/cm2 for 20 seconds. The plate was reversed so that the lower side of the plate was on top. The composite was once again irradiated for the same irradiation times.

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