# Antibacterialarial Agents Used in Modifications of Dental Resin Composites: A Systematic Review
## 4 Discussion
### Modification of RBC Compositions
#### 4.2.1 Organic Compounds and Monomers
Still, the long-time antibacterial activity, durability, and cytotoxicity of this composite should be analyzed. [PERSON] et al. [26] investigated the properties of an experimental composite resin containing the quaternary ammonium compound urethane-dimethacrylate (UDMQA-12). The modified antibacterial resin composite demonstrated biocompatibility and mechanical properties (flexural strength and modulus) comparable to those of the conventional composites used as controls. The antimicrobial activity of the modified material against _Streptococcus mutans_ was demonstrated, and cytotoxicity tests showed the material's biocompatibility. It would be useful to perform long-term cytotoxicity and mechanical strength tests to verify the safety and reliability of the material. [PERSON] et al. [27] synthesized three diquaternary ammonium methylacrylates that differed in alkyl chain length (biQAMA-12, biQAMA-14, and biQAMA-16). They concluded that the most optimal alkyl chain length was a 12-carbon chain. This dental composite material had the best antibacterial properties against _Streptococcus mutans_ due to its having the highest antibacterial charge density. Additionally, mechanical tests showed that modification of 5 wt% biQAMAs did not change the properties of the experimental material. Unfortunately, both biQAMA-14 and biQAMA-16 increased the cytotoxicity of the prepared composites. Also, the modification affected water sorption--its value increased but was still within the ISO standard. The increase in water sorption, although within the ISO standard, can vary over time. Long-term studies should be carried out to investigate whether the strength of the material changes over time. Strategies may need to be found to limit the increase in water sorption. Figure 6: Dimethyl-hexadecyl-methacryloxyethyl-ammonium iodide (DHMAI). One monomer that may find use in the production of an antibacterial composite is the quaternary urethane-dimethacrylate ammonium derivative QAUDMA-m (where m corresponds to the number of carbon atoms in the N-alkyl substituent, this being 8, 10, 12, 14, 16, and 18 in the studies considered). [PERSON] et al. [28, 29] conducted a study showing that resin matrices containing QAUDMA-m 8/10/12 compositions were most effective against _Staphylococcus aureus_ and _Escherichia coli_. The occurrence of lower water sorption, hardness, and solubility in water was related to the elongation of the N-alkyl chain. As the N-alkyl chain lengthened from 8 to 10 carbon atoms, the elastic modulus and flexural strength increased. Furthermore, the copolymers exhibited high biocidal activity during pilot studies. Nevertheless, it is necessary to determine whether such biocidal activity will last in composites (after filling) and to investigate the long-term safety in conjunction with water sorption, the stability of the mechanical properties, and the cytotoxicity. Dimethylaminododecyl methacrylate (DMADDM) can be used as a promising, effective antibacterial modifier. [PERSON] et al. [30] used DMADDM at different concentrations (0%, 1.5%, 3%, and 5 wt%). The study showed that using 3 wt% of DMADDM did not affect the composite. DMADDM appeared to have the best antimicrobial properties against _Streptococcus mutans_. [PERSON] et al. [31] also incorporated DMADDM into commercial gioner (Beautiful II F03 A2, SHOFU Inc., Kioto, Japan) and applied it against _Helicobacter pylori_. In vitro trials revealed that the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of DMADDM were 6.25 ug/mL and 25 ug/mL, respectively. DMADDM-modified materials effectively reduced _Helicobacter pylori_ biofilm formation in reconstructions. The antibacterial activity of DMADDM appears promising, but cytotoxicity and long-term behavior studies need to be carried out to ensure safe use. Another monomer used in dentistry is methacryloyloxydodecylpyridinium bromide (MDPB; Figure 7). MDPB allows the preparation of composites with antibacterial properties [66, 67]. [PERSON] et al.