Effects of Whitening Toothpastes on Aesthetic and Mechanical Properties of Anterior Composite Restorations: A Preclinical Evaluation

This in vitro study aimed to evaluate color recovery after 7 and 15 days of brushing with six whitening toothpastes that have different whitening mechanisms on coffee-stained anterior microhybrid composite resin. It also investigated the effects of brushing on surface microhardness. Disc-shaped specimens (2 mm thick, 10 mm in diameter) were prepared from a microhybrid anterior composite resin (GC G-ænial Anterior) (n = 10) and immersed in a coffee solution for 5 days to induce discoloration. Afterwards, the specimens underwent brushing simulation for 7 and 15 days using six whitening toothpastes and a non-whitening control toothpaste (Sensodyne Pronamel). Color changes were measured using a spectrophotometer based on the CIEDE2000 system, and surface microhardness was assessed with a Vickers microhardness tester. Statistical analysis was performed using repeated-measures analysis of variance (ANOVA). After coffee staining, all specimens showed discoloration exceeding the clinical acceptability threshold (ΔE00 > 1.8). After 7 days of brushing, significantly greater color recovery was observed in the Signal Whitening System, Colgate Optic White, and Sensodyne Extra Whitening groups compared to other toothpaste groups (p < 0.05). By the end of the 15-day brushing period, all whitening toothpastes resulted in visually and clinically significant reductions in coffee-induced discoloration (ΔE00 > 1.8), with the highest color recovery noted in the Signal Whitening System group (ΔE00 = 2.52 ± 0.91). Regarding surface microhardness, significant increases were observed in all groups after brushing (p < 0.05). The Pronamel, Colgate Optic White, and Advance groups demonstrated significantly higher Vickers microhardness values compared to the Rocs group at the end of the 15-day period (p < 0.05).