Clinical Color Match and Marginal Discoloration of a Universal Shade Composite Versus a Multi-shade Nanohybrid Composite in Anterior Teeth

Introduction: Anterior composite restorations require precise color matching and long-term marginal integrity to achieve optimal esthetic outcome. The introduction of structurally colored single‑shade composites such as Omnichroma (Tokuyama Dental Corporation, Tokyo, Japan) has simplified shade selection by utilizing clinical color match (CCM), although their long-term clinical performance relative to conventional multi‑shade composites remains uncertain. The present observational study aimed to compare the CCM and marginal discoloration of a structurally colored universal‑shade composite (Omnichroma) with those of a conventional multi‑shade nanohybrid composite (Beautifil® II; Shofu Inc., Kyoto, Japan) in Class III and Class IV anterior restorations over a 12‑month follow‑up. Materials and methods: This prospective observational clinical study included 100 anterior restorations (50 per material) placed in 50 patients according to the inclusion criteria. Some participants contributed more than one restoration; therefore, the restoration was considered the primary unit of analysis. Restorations were evaluated at baseline and at one, three, six, nine, and 12 months using the modified United States Public Health Service (USPHS) criteria (Alpha, Bravo, Charlie) for restoration appearance (CCM) and marginal integrity (marginal discoloration). Inter‑examiner agreement was assessed using Fleiss’ kappa. Data were analyzed using generalized estimating equations (GEE) and cumulative link mixed models, with significance set at p < 0.05. Results: For restoration appearance, Omnichroma demonstrated significantly higher clinically acceptable (Alpha+Bravo) rates from six months onward (98% vs. 92% at six months; 94% vs. 80% at 12 months; p < 0.01). The odds ratio for maintaining a clinically acceptable appearance (Charlie) with Beautifil II was 3.42 (95% CI: 1.38-8.47, p = 0.008). For marginal integrity, no statistically significant differences were observed between the materials at any time point, with identical Charlie rates (6%) at 12 months (p > 0.05). Inter‑examiner agreement was substantial to almost perfect (κ = 0.79-0.84). Conclusion: Within the limitations of this 12‑month observational study, the structurally colored universal‑shade composite (Omnichroma) provided superior CCM compared to the conventional multi‑shade nanohybrid composite (Beautifil II), while both materials exhibited equivalent marginal integrity. Omnichroma simplifies the restorative workflow without compromising the marginal seal, making it a favorable option for anterior Class III and IV restorations.