Clinical evaluation of a new chemically-cured bulk-fill composite in posterior restorations: 18-Month multicenter double-blind randomized clinical trial

Objectives: To evaluate the clinical performance of a novel self-cured bulk-fill composite (Stela Automix and Stela Capsule, SDI) with a light-cured bulk-fill composite (Filtek One, Solventum) after 12 and 18 months. Methods: A total of 165 Class I or Class II posterior restorations were placed in 55 participants. The self-cured composite groups received Stela primer followed by either Automix or Capsule forms. The light-cured group received Scotchbond Universal adhesive and the composite. Restorations were evaluated at baseline, 12, and 18 months using updated FDI criteria. Inter-group differences were analyzed using Friedman repeated measures ANOVA, and intra-group with Chi-square test (α = 0.05). Results: After 12 months, 17 restorations exhibited marginal staining, with no differences between groups (p = 1.00), but a significant intra-group change in both the self-cured (Capsules) and light-cured groups compared to baseline (p = 0.02). Regarding surface luster and texture, 30 restorations were considered clinically good, with a significant difference favoring the light-cured composite (p = 0.03), but no significant intra-group differences (p > 0.20). For color match, 32 restorations were rated as good, with a statistically significant result favoring both self-cured composites (p = 0.03), and no intra-group changes (p > 0.20). At the 18-month recall, the number of restorations rated as good was 22 for surface luster and texture, 27 for marginal staining, and 40 for color match; among these, only marginal staining showed significant intra-group changes (p < 0.006). Conclusion: After 18 months, the self-cured composite (Stela), whether Automix or Capsule, showed comparable functional and biological performance to the light-cured bulk-fill composite. Clinical significance: The self-cured bulk-fill composite is a reliable alternative for posterior restorations. Despite minor aesthetic differences, clinical outcomes and patient satisfaction were unaffected, supporting its use in daily practice.