Clinical performance of short fiber-reinforced and indirect resin composites in class I and class II restorations: A three-year randomized clinical trial

Objective: This prospective randomized clinical trial was designed to evaluate and compare the three-year clinical performance of short fiber-reinforced composite (SFRC) and indirect laboratory (lab) composite with that of a microhybrid resin composite placed in Class I and Class II cavities, with marginal adaptation defined as the primary outcome. Materials and methods: Thirty-three participants, each exhibiting 3 posterior carious teeth (Class I or II, ICDAS 4 or 5) under stable occlusion, were enrolled in this study. A total of 99 restorations (33 for each material) were placed as follows: SFRC (everX Posterior), indirect lab composite (SR Nexco), and microhybrid resin composite (G-aenial Posterior). Clinical assessments were conducted at baseline (1 week), 6 months, 1, 2, and 3 years by two blinded examiners utilizing FDI criteria, with marginal adaptation designated as the primary outcome, whereas other FDI criteria were assessed as secondary outcomes. Intragroup differences across follow-ups were assessed using Friedman and Wilcoxon post-hoc tests, while intergroup comparisons were analyzed using Kruskal-Wallis and Mann-Whitney U tests. The significance level was set at α = 0.05. Results: Twenty-eight patients with a total of 84 restorations were evaluated at the end of the 3-years with 84.45% recall rates. The outcomes revealed no statistically significant differences among SFRC, indirect lab composite, and microhybrid resin composite restorations for the assessed criteria (p > 0.05). The clinical success rates for SFRC (everX Posterior), indirect lab composite (SR Nexco), and microhybrid resin composite (G-aenial Posterior) were 100%, 100%, and 96.43%, respectively. Conclusion: After a three-year follow-up period, both SFRC and indirect lab composite demonstrated acceptable clinical performance, comparable to that of microhybrid resin composite, as evaluated by the FDI criteria. Clinical significance: Although the tested resin composite materials revealed similar clinical behavior in posterior teeth, the prolonged treatment time and higher cost of indirect lab composite favor the direct approach. © The Author(s) 2025.