Effect of Polishing and Additional Polymerization on Color Stability of Composite Resins

Objective: The aim of this study was to investigate the effect of polishing and additional polymerization on color stability in a nanohybrid composite resin. Methods: In this study, 72 composite disk-shaped samples (8*8*2mm) were prepared from a nanohybrid composite (Clearfil Majesty Esthetic, Kuraray, Japan). The samples were polymerized in standard mode (1000 mW/mm2/20sn) with a LED curing device (VALO™Grand, Ultradent, USA) and divided into 3 groups according to polishing treatments; control (unpolished, group1), aluminum oxide discs (group 2/Softex, 3M, USA) and diamond polishing paste (group3/Diamond Polish Mint, Ultradent, USA). Then, in each polishing group, half of the samples remained in the initial polymerization (subgroup a), while the other half were polymerized for an additional 20 s in standard mode (subgroup b). Color was measured with a spectrophotometer (VITA Easy ShadeV, VITAZahnfabrik, Germany) initially and after 1 week of storage in coffee. Color change (ΔE00) was calculated with CIEDE2000 formula. Data were analyzed by Two Way ANOVA, One Way ANOVA, Post-hoc Tukey, and Independent t test in SPSS software (α=.05). Results: The effect of polishing type and additional polymerization on the color stability of the tested material was statistically significant (p<.001). Additional polymerization reduced discoloration in all polishing groups. This reduction was statistically significant in groups 1 (p=.003) and group 2 (p=.001). The least discoloration was obtained in group 3b (4.42±0.81) and the most discoloration was obtained in group 2a (7.98±1.86). Conclusion: Diamond polishing pastes and additional polymerization were found to be beneficial in the color stability of tested material.