Deep margin elevation in class II cavities: A comparative evaluation of microleakage and interface integrity using confocal laser microscopy and scanning electron microscopy

Aim: This study aims to evaluate the microleakage between the gingival seat and base material and to assess the interface integrity between the base material and overlying composite in class II cavities restored using deep margin elevation. Materials and Methods: Thirty maxillary molars ( n = 30) were taken, and class II cavities were prepared with a gingival seat extending below the cementoenamel junction. These teeth were divided into three groups for subgingival margin elevation using different materials: Group A ( n = 10) – flowable composite, Group B ( n = 10) – glass ionomer cement (GIC), and Group C ( n = 10) – GIC with nanohydroxyapatite (GIC n-HAp). The remaining cavities were restored with bulk-fill composite. After undergoing 1000 thermocycling cycles, half of the samples were examined for microleakage using confocal laser microscopy, and the other half were assessed for interface integrity using scanning electron microscopy. Microleakage was statistically analyzed by one-way ANOVA, and interface integrity was analyzed by Kruskal–Wallis tests. Results: The study found that GIC n-HAp exhibited significantly lower microleakage between the base material and gingival seat than flowable composite and GIC. However, regarding interface integrity between the base material and bulk-fill composite, flowable composite, and GIC outperformed GIC n-HAp. Conclusions: Incorporating n-HAp into GIC effectively reduced microleakage at the dentin-base material interface. However, the interface integrity between GIC n-HAp and the composite poses a challenge.