In Vitro Evaluation of Oral Irrigator-Assisted Mouthrinse Application on Color Stability of Single-Shade Nanohybrid...

Color stability is a key determinant of the long-term esthetic performance of resin-based restorative materials. Single-shade nanohybrid resin composites, developed to simplify shade selection, remain susceptible to extrinsic discoloration and routine oral hygiene procedures. This study aimed to evaluate color stability following coffee staining and subsequent use of different mouthrinse formulations applied with or without an oral irrigator. Disc-shaped specimens were fabricated, stained with coffee, and subjected to mouthrinses using either static immersion or oral irrigator-assisted delivery. Color measurements were obtained at baseline, after staining, and after mouthrinse application, and color changes (ΔE₀₀) were calculated for discoloration after coffee staining (ΔE₁), color change after mouthrinse application (ΔE₂), and total color change (ΔE₃) using the CIEDE2000 formula. Statistical analysis was performed using robust three-way ANOVA with trimmed means. Surface morphology was additionally evaluated using environmental scanning electron microscopy. The results demonstrated that coffee staining resulted in a clinically unacceptable color change in all groups (ΔE₀₀ > 0.8). Composite type significantly influenced color change after coffee staining (ΔE₁) and total color change (ΔE₃) (p < 0.001). Mouthrinse type significantly affected color change after mouthrinse application and total color change (ΔE₂ and ΔE₃) (p = 0.001). Application method significantly affected total color change (ΔE₃) (p < 0.001). Subgroup analysis revealed that within the Charisma Diamond One composite (DO), ΔE₃ values were significantly higher in the oral irrigator group compared to direct immersion (p = 0.001), and within the irrigator group, the DO composite exhibited significantly higher ΔE₃ values than the Vittra APS Unique composite (p = 0.001). These findings demonstrate that composite formulation and mouthrinse application method significantly influence post-staining color stability, with oral irrigator use exacerbating discoloration in certain materials. Clinically, this suggests that restorative material selection and oral hygiene practices should be carefully considered to minimize esthetic degradation.