Evaluating the Marginal Seal of Bioactive Restorative Material and Two Bulk-fill Composites in Class II Restorations: An In Vitro Study

Background: Marginal microleakage remains a major concern in posterior composite restorations, contributing to recurrent caries, postoperative sensitivity, pulpal irritation, and eventual restoration failure.Polymerization shrinkage stress and poor marginal adaptation are significant factors influencing seal integrity in Class II restorations.Bulk-fill composites have been developed to overcome these limitations through improved depth of cure and reduced shrinkage stress, whereas bioactive restorative materials such as Cention-N aim to enhance remineralization potential.Objectives: The aim of this study was to assess and compare the marginal microleakage of a bioactive restorative material, Cention-N, with two bulk-fill composite materials (Surefil and Tetric N-Ceram) in standardized Class II cavities using a dye-extraction spectrophotometric method.Materials and methods: Thirty extracted human mandibular first molars were selected, and uniform Class II cavities were prepared on the mesial surfaces.The teeth were randomly categorized into three groups (n = 10): Group I-Cention-N; Group II-Surefil® bulk-fill composite; and Group III-Tetric N-Ceram bulk-fill composite.Cavity surfaces for Groups II and III were etched, bonded, and light-cured following the respective manufacturers' instructions, whereas Cention-N was bulk-placed and allowed to self-cure.After restoration, all specimens were finished, polished, and stored at 37°C for 24 hours.Microleakage was evaluated using the dye-extraction technique, and absorbance values were measured spectrophotometrically.Statistical comparisons were performed using one-way analysis of variance (ANOVA) followed by Tukey's post-hoc test, with the significance level set at p < 0.05.Results: Statistically significant differences were observed among the groups.Surefil exhibited the least microleakage, followed by Tetric N-Ceram, while Cention-N demonstrated the highest dye penetration, indicating inferior marginal sealing ability compared to bulk-fill composites (p < 0.05).Conclusion: Surefil and Tetric N-Ceram bulk-fill composites demonstrated superior marginal sealing performance compared to Cention-N in Class II restorations.Within the limitations of this in vitro study, bulk-fill materials are preferable options for minimizing microleakage, whereas Cention-N may be recommended when bioactivity is clinically prioritized and adhesive systems are used.