The effects of three whitening toothpastes on the color stability, microhardness, and surface roughness of contemporary one‑shade composite systems

BACKGROUND: The aim of this study was to evaluate the mechanical (surface roughness & microhardness) and optical (color stability) properties of two modern one-shade dental composites following exposure to three different whitening toothpastes. METHODS: A total of 192 disc-shaped specimens (n = 8; per subgroup) were prepared from two one-shade composites: ONE (Charisma One, Kulzer, Germany) and VITTRA APS (Advanced Polymerization System) Unique (FGM, Germany). Specimens were assigned to four brushing media: Opalescence Whitening, Signal White Now Glossy Shine, Colgate Optic White Expert, and distilled water (control). Discs (2 mm × 10 mm) were fabricated using a Teflon mold, stored at 37 °C for 24 h in tab water. Microhardness (Vickers; 200 g/10 s), surface roughness (contact profilometry), and color parameters (VITA Easyshade V; CIEDE2000) were recorded before and after a toothbrushing simulation of 10,000 cycles. Toothpastes were used as a 1:3 (v/v) slurry. Data were analyzed using two-way ANOVA with Tukey's HSD test (p < 0.05). RESULTS: All surface roughness values increased after toothbrushing; the greatest change was observed in the VW group (0.056 ± 0.017), whereas the smallest change occurred in the OCO group (0.006 ± 0.040) (p < 0.05). In all subgroups, microhardness values decreased following brushing, and the most pronounced reduction was found in the OW group (-10.12 ± 3.24). This decrease was statistically significant when compared with the OS, OC, OCO, and VW groups (p < 0.05). With respect to color stability, only the VW group remained below the clinically acceptable threshold (ΔE₀₀ = 1.8). Nevertheless, no statistically significant differences were detected among the experimental groups. Nor, interestingly, did any group other than VW exhibit a change that fell within the clinically acceptable range. CONCLUSION: The compositional architecture and formulation of dental composites, in conjunction with toothpaste constituents, may lead to divergent outcomes when subjected to various mechanical tests.