Long-Term Clinical Performance of Posterior Composite Restorations After Nearly Three Decades: A Clinical Follow-Up Study

Background/Objectives: Long-term clinical data on direct posterior composite restorations are scarce. This study evaluated their performance after almost three decades using selected FDI criteria. Temporal changes were tracked across follow-up exams, including within a predefined subcohort. Methods: This observational follow-up involved 21 patients with 57 posterior composite restorations placed in 1995–1996. The 2025 follow-up used FDI criteria to assess functional, esthetic, and biological properties, classifying outcomes as clinically acceptable, intervention needed, or failure. Descriptive analyses were applied to the entire cohort. Longitudinal analyses were conducted on a subcohort of 14 patients with 27 restorations at three time points. Exploratory analyses assessed associations with restoration factors, caries experience, and gingival health. Results: In 2025, 54.4% of restorations were clinically acceptable, 28.1% required intervention, and 17.5% were failures. Functional criteria remained mostly acceptable, though form and contour showed the highest mean values. In the longitudinal subcohort, significant changes over time were observed in anatomical form and occlusal wear. Retention, marginal adaptation, proximal contact, and surface luster did not change significantly. Biologically, restorations available for direct assessment had low incidences of secondary caries, hard-tissue defects, and postoperative sensitivity or pulpal issues. Conclusions: Posterior composite restorations can function for nearly three decades but gradually deteriorate in certain aspects. Long-term changes mainly involve cumulative functional aging of the anatomical form and occlusal wear, rather than widespread biological failure. These findings underline the importance of differentiated long-term assessment and support conservative management approaches where clinically feasible before replacement is undertaken.