## 3 Results
### Biocompatibility  
Biocompatibility was also assessed in some of the articles selected for this systematic review. Cytotoxicity was assessed in six articles using human oral fibroblasts. Proteinadsorption test was investigated in one article [19], the blood compatibility test in one article [16], and genotoxicity [39].  
In the case of the incorporation of zirconia nanoparticles (ZrO\({}_{2}\) NPs), the group with the highest cell proliferation was the one with 5% ZrO\({}_{2}\) NPs in the acrylic resin [13]. When graphene nanoplatelets were incorporated, the viability of cells showed no significant differences between the tested groups and the control group [14]. For the Ag/MSN, cell viability was found to be dependent on their concentration in the PMMA resin, as high cell viability was observed in the groups with 0.025% and 0.05% Ag/MSN compared to the other groups [15] (Table 2).  
To analyze the effects of the bioactive glasses on PMMA resin, the growth of fibroblasts was examined after 24 h with the PrestoBlue assay and after 96 h with methylthiazolyl diphenyl tetrazolium bromide. It was found that cell viability was not affected after 24 h of incubation, but after 96 h of incubation, cell viability decreased in all groups with bioactive glasses compared to the control group [35]. The adsorption of proteins was also investigated in conjunction with the zwitterionic materials. The analysis of the results showed that the adsorption decreased and was lower in the groups with this compound than in the control group [19] (Table 2).  
For the titanium dioxide and PEEK nanoparticles, the cytotoxicity of the groups was analyzed using the CCK-8 assay. This parameter was evaluated for 7 days, and it was found that the groups showed adequate cytocompatibility with these compounds. Blood compatibility was also tested in this study, including hemolysis and analysis of blood coagulation parameters such as activated partial thromboplastin time (APTT) and prothrombin time (PT). The APPT was approx. 36.5 s, and the PT approx. 13.5 s, thus within the normal range. It was concluded that the groups, both the control group and the groups with the nanoparticles, had good blood tolerance [16] (Table 2).  
Regarding the incorporation of cellulose nanocrystals reinforced with silver, they show that these exhibit no significant toxicity in L929 fibroblasts compared to the control group. The survival rate of the cells was more than 85% in all groups studied [17]. In the case of titanium dioxide nanoparticles in acrylic resin, cytotoxicity was investigated in two acrylic resins, E-Dent 100 (dent-PMMA) and E-Denture (base-PMMA). In the case of the dent-PMMA material, the extract test was used for the different groups studied (control group, 1% nanoparticles, and 4% nanoparticles), and it was found that the group with the highest viability was the control group, followed by the group with 1% nanoparticles. In the case of the PMMA base matrix, it was evaluated with the XTT method, and there were no differences in the cytotoxic effect between the groups studied [39]. Genotoxicity was evaluated using the micronucle test (Mtvit) for the two groups, base PMMA without titanium dioxide nanoparticles and base PMMA + 0.4% TiO\({}_{2}\) nanoparticles, and it was found that the TiO\({}_{2}\) nanoparticles caused hardly any DNA damage compared to the negative control group [39] (Table 2).