Color stability of a bulk-fill composite resin light-cured at different distances

Abstract The aim of this in vitro study was to evaluate the color stability of a bulk-fill (Filtek One Bulk Fill, 3M ESPE) and a conventional (Filtek Z350 XT, 3M ESPE) composite resin light-cured at different distances, before and after being submitted to staining with a coffee solution. Sixty specimens of each composite resin were prepared and light-cured at distances of 0, 2 and 4 mm, using a LED light-curing unit (Valo, Ultradent). The specimens were separated (n = 10) for immersion in either distilled water or coffee solution (10 minutes a day for 8 days) to stimulate staining. Color evaluations were performed before and after immersion in the solutions, according to CIELab (△Eab), CIEDE2000 (△E00) and the Whiteness Index for Dentistry (△WID). Kruskal Wallis and Dunn tests, Mann-Whitney tests and Wilcoxon test were applied (α = 5 %). The a* value for conventional composite resin showed a significant increase after immersion in coffee and distilled water (p < 0.05). Both composite resins showed greater b* values when immersed in coffee than in distilled water, with no significant difference among the light-activation distances (p > 0.05). There was no significant difference for L* among the light-activation distances; both resins showed significant decrease in L* after immersion in coffee (p < 0.05). Color change (△Eab, △E00) and difference in whiteness (△WID) were higher for conventional resin when immersed in the coffee solution at all the light-activation distances. Conventional composite resin presented a higher staining value than bulk-fill composite resin, regardless of the light-activation distance.

摘要
本体外研究旨在评估分别以不同距离光固化的大块充填复合树脂（bulk-fill，Filtek One Bulk Fill，3M ESPE）与常规复合树脂（Filtek Z350 XT，3M ESPE）在经咖啡溶液染色前后的颜色稳定性。本研究共制备两种复合树脂试件各60个，采用LED光固化机（LED light-curing unit，Valo, Ultradent）分别以0、2、4 mm的距离进行光固化。将试件按每组10个分为亚组，分别浸泡于蒸馏水或咖啡溶液中（每日10分钟，持续8天）以模拟染色过程。分别在浸泡前后，依据CIELab色空间（△Eab）、CIEDE2000色差公式（CIEDE2000，△E00）及牙科用白度指数（Whiteness Index for Dentistry，△WID）开展颜色评价。统计学分析采用Kruskal-Wallis秩和检验、Dunn检验、Mann-Whitney U检验及Wilcoxon符号秩检验，检验水准α=0.05。常规复合树脂的a*值在经咖啡溶液及蒸馏水浸泡后均显著升高（p<0.05）。两种复合树脂经咖啡溶液浸泡后的b*值均高于蒸馏水浸泡组，且不同光固化距离间的b*值差异无统计学意义（p>0.05）。不同光固化距离间的L*值差异无统计学意义；两种复合树脂经咖啡溶液浸泡后L*值均显著降低（p<0.05）。在所有光固化距离下，常规复合树脂的色差（△Eab、△E00）及白度变化值（△WID）均高于大块充填复合树脂。无论光固化距离如何，常规复合树脂的染色程度均高于大块充填复合树脂。