## 4 Discussion
### Study Results  
The decrease in microleakage observed in RMGIC compared to conventional GIC could be attributed to differences in their setting reactions. In conventional GIC, if it encounters intraoral fluid during the initial setting, the matrix-forming ions (Ca and Al) may be washed out, resulting in improper matrix formation with inferior mechanical properties and increased microleakage. In contrast, RMGIC undergoes two setting processes: acid-base reaction and photopolymerization. In this process, hydroxyl ethyl methacrylate partially replaces water. The structure of RMGIC includes a matrix of metal polyacrylate salts and a polymer matrix. Consequently, RMGICs are generally considered less affected by moisture, exhibiting reduced microleakage compared to conventional GICs [41]. However, [PERSON] and [PERSON] [52] also concluded that Fuji II LC performed worse than Fuji II at the enamel margin but was comparable at the dentin cement margin. However, in the same study, Photac Fil showed a significantly more reliable seal than KetacFil at both the occlusal and gingival margins. The authors proposed that this could be attributed to the encapsulation of ESPE materials (Photac Fil and Ketac Fil). Meanwhile, the Fuji II LC and Fuji II were not capsulated, and individual hand proportions and mixing can affect the results. Nano-filled RMGIC (Ketac N100) is a new RMGIC that was introduced in 2007. Two studies [45; 47] performed on permanent teeth provided valuable insights on the performance of Ketac N100 compared to conventional GICs and other RMGICs. However, the study by [PERSON] et al. [45] observed that there was no significant difference between the Fuji LC II and KN100 in Class I restoration. In contrast, a significant difference was obtained in Class V restorations. These results are consistent with those obtained by [PERSON] et al. [47], who found that Ketac N100 showed less leakage than conventional GIC and RMGIC at gingival margins. This could be due to smaller particle sizes providing better material flow and better adaptation to the tooth interface; also, the higher filler loading in the nano-filled type may result in lower polymerization shrinkage and a lower coefficient of thermal expansion, thus improving long-term bonding to the tooth structure. Additionally, the incremental layer technique used to place Ketac N100 may have further improved adaptation, leading to Ketac N100 showing less leakage and better performance than conventional GICs and other RMGICs. The manufacturer and some authors refer to Activa Bioactive Restorative as a bioactive composite [65; 66; 67], but others consider it an RMGIC [27; 68]. The components of Activa Bioactive Restorative are a proprietary bioactive ionic resin, a proprietary rubberized resin, and a bioactive glass ionomer; therefore, it was included in our research. We found only one study [27] that compared it with the GIC Equia Fil and the RMGIC Fuji II LC and demonstrated that they exhibited the same marginal adaptation and microleakage. Carbomer Glass Fil is a new material that consists of nanosized hydroxyapatite-fluorapatite particles in powder form. Only one study evaluating permanent teeth [44] found higher microleakage and crack lines filled with dye in the glass carbomer. Despite the advantages of glass carbomer material, there is a need for improvements, particularly in its sealing capacity, for it to be considered a reliable restorative material. Zirconomer Improved, a new restorative glass ionomer material (also called white amalgam because it combines the strength of amalgam with the biocompatibility and fluoride release of GICs), was evaluated in one study, and it was observed that they offer better leakage resistance than glass carbomer, conventional GICs, and RMGICs and might be considered as a reliable posterior restorative material, especially for patients with high caries activity [44]. Equia Forte is a glass hybrid restorative system that combines the benefits of GIC and composite resin.