Decoding marginal adaptation and microleakage: A field emission scanning electron microscopy and stereomicroscopic evaluation of cavity liners under class II composite restorations

Abstract Context: Esthetics are in high demand in modern dentistry; conservative dentistry offers tooth-colored restorative materials; however, drawbacks such as polymerization shrinkage can lead to microleakage. To minimize this problem, cavity liners are used. Aim: To compare the marginal adaptation and microleakage of different cavity liners under composite restorations using field emission scanning electron microscopy (SEM) and stereomicroscope, respectively. Subjects and Methods: Sixty extracted human premolars and molars were collected, and Class II cavities involving the distal and occlusal surfaces were prepared. The samples were randomly divided into four groups: Group I – Biodentine, Group II – Resin Modified Glass Ionomer Cement (RMGIC), Group III – Resin-modified calcium silicate (TheraCal LC), and Group IV – Direct composite without cavity liner (control). After liner application in Groups I–III, all cavities were etched, bonded, and restored with composite. The teeth were then immersed in 2% buffered methylene blue dye and sectioned longitudinally in the mesiodistal direction. Statistical Analysis Used: Marginal adaptation was evaluated under a stereomicroscope, and interfacial gaps were examined using SEM the Kruskal–Wallis test and post hoc ANOVA (Bonferroni) were used for statistical analysis. Results: TheraCal LC showed the least microleakage, followed by Biodentine and RMGIC, while the control group exhibited significant microleakage. SEM analysis revealed no significant difference between TheraCal LC and Biodentine in marginal adaptation, with the largest gaps observed in the control group. Conclusion: TheraCal LC demonstrated superior performance in terms of both microleakage and marginal adaptation and may be preferred as a cavity liner in Class II cavities.