Charcoal whitening agents and composite resin: investigating color change and surface roughness

This study aimed to investigate the effects of different charcoal-based whitening products on the color stability and surface roughness of resin composite, following coffee-induced staining and subsequent brushing with whitening products.

Fifty disc-shaped specimens of Harmonize nanohybrid composite resin were fabricated and divided into five groups (n = 10 per group): Control (untreated), Colgate Total (CT), Colgate Total + Charcoal Solution (CT + CS), Colgate Charcoal (CC), and Charcoal Powder (CP). The specimens were immersed in coffee for five days to simulate staining, followed by brushing with the respective whitening products. Color changes (ΔE₀₀) were evaluated using the CIEDE2000 formula, and surface roughness was measured with a non-contact profilometer. Color and roughness analyses were performed at three stages: baseline, post-staining and post-whitening. SEM (Scanning Electron Microscopy) analysis was conducted descriptively at the end of the study to observe surface morphology. Statistical analysis was conducted using one-way ANOVA and post-hoc Tukey tests (p ≤ 0.05).

All experimental groups showed significant color changes after staining (ΔE_00 - 1>1.8, p ≤ 0.05). The CP group exhibited the highest color change after whitening (ΔE_00 - 2 = 7.13 ± 1.38, p ≤ 0.05). Surface roughness increased significantly in the CT + CS (Ra = 0.57 ± 0.22 μm) and CP (Ra = 0.54 ± 0.20 μm) groups (p ≤ 0.05). No significant differences in surface roughness were observed in the regular toothpaste and charcoal toothpaste groups (p > 0.05). SEM analysis revealed pronounced surface irregularities, particularly with CP treatment.

Charcoal-based whitening products significantly affected color stability and surface roughness, with the CP group showing the greatest adverse effects. Regular and charcoal toothpastes had no significant impact on surface roughness, indicating a safer profile.