# Antibacterialarial Agents Used in Modifications of Dental Resin Composites: A Systematic Review
## 4 Discussion
### Modification with Released Agents  
Released antimicrobial agents (Figure 4) are substances incorporated into composite materials that are released over time into the oral cavity. One such substance is tricolson (TCN), which is used, for instance, in the production of toothpastes and mouthwashes. It is characterized by antibacterial properties against _Staphylococcus aureus_, _Streptococcus mutans_, _Lactobacillus_ species, and _Actinomyces_. [PERSON] et al. [18] decided to mixed trichosencapsulated halloysite nanotubes (HNT/TCNs) with RBCs. Their study showed no changes in the antibacterial properties of the modified composites over 5 days and some improvements in their mechanical properties and an increase in polymerization stress. But, as stated by the authors, the antimicrobial test methods may not be fully suitable for comprehensively evaluating composites, and it is worthwhile for them to be accompanied by aging protocols. [PERSON] et al. [19] attempted to obtain antimicrobial properties by incorporating a deeply eutectic solvent (DES) derived from the antimicrobial agent benzalkonium chloride (BC) mixed with acrylic acid (AA). The composite containing DES (DES-C) exhibited superior flexural strength and biocompatibility compared to a similar composite incorporating BC (BC-C) at equivalent BC levels. Although both BC-containing composites demonstrated  
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antibacterial activity, BC-C produced larger inhibition zones than DES-C at equivalent BC concentrations (against _Streptococcus mutans_ and _Staphylococcus aureus_). Control composites without BC showed minimal antibacterial activity. Following artificial aging, DES-C maintained mechanical properties better than BC-C compared to the control, albeit with a slight decrease observed during the three-point bending test, especially under elevated-temperature storage conditions. Chlorhexidine is a commonly used antiseptic that acts against Gram-negative and Gram-positive bacteria, parts of viruses, molds, and yeast. It is used in oral fluids to reduce post-operative infections and inflammation of the gums [20]. Additionally, chlorhexidine can also be used as an antimicrobial modifier for polymethylmethacrylate (PMMA) [61; 62]. Montmorillonite clay (MMT) is used as a carrier for drugs or macromolecules, such as DNA, proteins, and nucleotides [63]. [PERSON] et al. [20] used MMT enriched with chlorhexidine (CHX/MMT) to modify RBCs. CHX/MMT, in addition to having antibacterial properties, can reinforce the structure of composites. In their study, the antimicrobial activity of experimental composite materials against _Porphyomonas gingivalis_ was tested. They showed that materials enriched with 5 wt% of MMT and 10 wt% chlorhexidine (Figure 5) achieved the best inhibitory properties. The modification with CHX/MMT did not adversely affect elastic modulus or flexural strength values or the degree of conversion of the composites. Another idea for achieving antibacterial properties was conceived by [PERSON] et al. [21]. They decided to use a composite enriched with a light-cured AgBr core-shell/cationic polymer nanocomposite (AgBr/BHPVP). The Ag\({}^{+}\) released from the material acts against _Streptococcus mutans_. Such a material seems promising and capable of reducing the appearance of secondary caries. Evaluation of its cytotoxicity, however, showed that materials modified with less than 1 wt% of AgBr/BHPVP obtained results similar to the control. The study also showed that the modification increased the hardness of the material and did  
Figure 4: Released modificator. Figure 5: Layers of MMT with Chlorhexidine. not negatively affect its elastic modulus or flexural strength. Nevertheless, it needs to be evaluated whether this substance would have similar effectiveness in filled materials. [PERSON] et al. [64] used fluorapatite (FA) crystals as a secondary filler. The crystals were introduced into material at 10, 20, 30, and 40% by weight.