Background: Marginal integrity at sub-cementoenamel junction (CEJ) margins remains a clinical challenge in posterior composite restorations. Polymerization shrinkage and interfacial stress contribute to microleakage and restoration failure. The present in vitro study compared cervical microleakage among four restorative approaches in Class II cavities extending below the CEJ. Materials and Methods: Forty extracted human maxillary first premolars were prepared with standardized Class II box-only cavities (gingival margin 2 mm below CEJ) on both sides, thereby yielding a total of n = 80 restorations. Specimens were divided into four groups ( n = 20) according to the restorative technique: Resin-modified glass ionomer cement (RMGIC) liner + nanohybrid composite (Group 1); flowable liner + nanohybrid composite (Group 2); incremental composite technique (Group 3); and bulk-fill composite (Group 4). Following thermocycling and fluorescein dye immersion, sections were examined under a stereomicroscope (×40), and leakage was scored on a four-point scale. Data were analyzed using Kruskal–Wallis and Dunn’s post hoc tests ( P < 0.05). Results: All groups showed some degree of leakage. Mean dye penetration scores were: Group 1 = 3.75 ± 0.55, Group 2 = 3.65 ± 0.67, Group 3 = 1.90 ± 1.77, and Group 4 = 2.00 ± 1.72 ( P < 0.05). Incremental and bulk-fill techniques demonstrated significantly less cervical microleakage than RMGIC-and flowable-lined restorations. No significant difference existed between Groups 3 and 4. Conclusion: Incremental and bulk-fill placement techniques achieved superior marginal sealing compared with restorations using RMGIC or flowable liners. Liners did not improve sub-CEJ sealing and may increase interfacial stress. Simplified adhesive strategies using low-shrinkage composites can enhance long-term marginal integrity.
Ahirwal et al. (2025) studied this question.