Color stability of a novel self-cure bulk-fill composite compared to light-cure bulk-fill and injectable composite resins

Abstract

Objective: This study aimed to assess the color stability of a novel self-cure bulk-fill composite (automix and capsule forms), in comparison to a light-cure bulk-fill composite and a conventional flowable composite after immersion in common beverages. Materials and methods: Four composite resins (Stela Automix, Stela Capsule, Filtek Bulk Fill Flowable, and G-ænial Universal Injectable) were evaluated on 160 disc-shaped specimens. Specimens were randomly assigned to four subgroups (n = 10) and immersed in tea, coffee, cola, or distilled water (control). Color measurements were performed using a spectrophotometer at baseline, 6 and 12 days, and color changes (ΔE₀₀) were calculated using the CIEDE2000 formula. Statistical analyses were performed using one-way ANOVA with Tukey’s post-hoc tests and paired sample T-tests to evaluate time-dependent changes (p < 0.05). Results: All composites showed increased discoloration over time, with coffee causing the most significant color change, followed by cola, while tea had a milder effect. Self-cure bulk-fill composites showed significantly higher ΔE₀₀ values than their light-cure composites. Stela Automix showed the greatest color change after Stela Capsule. Conclusion: The results suggest that self-cure bulk-fill composites have lower color stability than light-cure composites. Filler characteristics, particularly particle size and loading, have a greater influence on color stability than resin matrix composition.