Also, there were significant differences between polymerization promotion with LED and autoclave and the HQTH light curing unit (P<.05). The CIE a* value was not affected by polymerization methods. The CIE a* value shifted toward green (��a*< 0). But, there were no significant differences among groups (P>.05). The CIE b* value was affected by polymerization methods (P<.05). The CIE b* values of the inlay oven polymerization group is significantly differences from the other four groups (P<.05). The composite resins polymerized with the inlay oven showed the highest ��*b values which means less yellow color in specimens. For all groups, CIE L* values decreased after polymerization, all specimens became darker during investigation (��L*< 0). In all groups, C*ab and CIE a* values decreased after polymerization (P<.
05). The CIE a* value shifted toward green (��a*< 0). CIE b* values decreased after polymerization (��b*< 0), indicating the increase of blue color and the decrease of yellow color factor (P<.05). There were significant differences b1 and b0 (after and before) in the inlay oven polymerization group, LED and autoclave, LED, and HQTH (P<.05). Mean changes in color and color parameters by the polymerization methods are presented in Figure 1. Figure 1 Mean changes in color parameters by the brand of resin composites. DISCUSSION This in vitro study measured the amount of the changes in color and color parameters of composite resin material polymerized by five different polymerization methods.
Based on the results of the present study, the first null hypothesis of the present study that the polymerization methods don��t affect the color parameters of composite resin material was partially accepted because color change was not affected by polymerization methods. However, C*ab and b* values were affected by polymerization methods. The second null hypothesis that there is no color difference between unpolymerized and polymerized composite resin regarding the polymerization methods was accepted. The results of the present study demonstrated that there were color changes in all groups. ��E*ab values of specimens were 3.3. The lowest color change (��E*ab) value was 3.3 in polymerization with LED and autoclave; the highest color change (��E*ab) value was 4.6 in polymerization with HQTH. The polymerization color changes of resin composites were investigated, and the range of color change was 2.
6�C4.1. ��E*ab units depended on the shade.27 Changes in CIE L* parameter (lightness) after polymerization were significant for all materials, Drug_discovery and changes in the lightness had the greatest influence on polymerization color change.27 In the current study, Filtek P60 A3 shade composite resin was used. There were no significant differences in ��E*ab value among the groups. In all groups, CIE L* value decreased after polymerization, but there were no significant differences among the groups.