Abstract
BACKGROUND: The cementation of indirect restorations is a critical step influencing their long-term clinical success. While dual-cure resin cements are widely used, injectable resin composites have emerged as promising alternatives, offering improved handling, high filler content, and esthetic stability. However, their clinical performance as luting agents for indirect restorations remains insufficiently explored. This trial assessed the clinical performance of indirect hybrid ceramic onlay restorations cemented with injectable resin composite versus dual-cure resin cement over 18 months. MATERIALS AND METHODS: A total of 28 participants were randomly assigned to two groups (n = 14) based on the cementation protocol. The intervention group received onlays cemented with injectable resin composite (BEAUTIFIL Flow Plus X F03, Shofu Dental Corporation), while the control group received dual-cure resin cement (BeautiCem SA, Shofu Dental Corporation). Standardized procedures were followed for cavity preparation, immediate dentin sealing, cavity optimization, impression-taking, onlay fabrication (SHOFU Block HC, Shofu Dental Corporation), and cementation. Restorations were evaluated at baseline, 6, 12, and 18 months using the modified USPHS criteria. Data were statistically analyzed with significance set at P ≤ 0.05. Intergroup comparisons were assessed with Chi-squared test, while intragroup comparisons were assessed with Cochran's Q test. Kaplan-Meier analysis and the log-rank test were used to evaluate survival rates. RESULTS: Inter- and intragroup comparisons revealed no significant differences between the two groups for most outcomes (P > 0.05). However, at 18 months, dual-cure resin cement exhibited significantly higher marginal discoloration than injectable resin composite (P = 0.038). Within the dual-cure resin cement group, a significant decline in alpha scores for marginal discoloration was observed from baseline to 18 months (P = 0.007). While no restorations failed (Charlie score), Kaplan-Meier survival analysis and the log-rank test demonstrated a statistically significant difference between the two groups (P = 0.029). CONCLUSIONS: After 18 months, injectable resin composite demonstrated acceptable and comparable clinical performance to dual-cure resin cement, with the added benefit of reduced marginal discoloration. CLINICAL RELEVANCE: Injectable resin composites offer a viable alternative to dual-cure resin cements for luting indirect restorations with enhanced esthetic outcomes. TRIAL REGISTRATION: https://clinicaltrials.gov/ , (NCT05954156), 20-07-2023.