## 3 Results and Discussion
### Swelling Abilities Study
Taking into consideration the fact that after 48 h, investigated materials stopped absorbing the swelling medium, it can be assumed that it should not cause any additional effects of prolonged exposure on mechanical integrity. Volumetric and dimensional stability is crucial for future applications in physiological environments, especially craniofacial areas, where dynamic stresses, including compression, tension, and shear forces, are present. Thus, the continuous swelling may alter the biomaterial's structural and mechanical properties. The choice of fairly stable in aqueous media PLA as a main raw material should potentially avoid this problem after in vivo application. Figure 10: General scheme of GBR procedure after tooth extraction: (**a**) healthy socket with tooth; (**b**) empty socket after tooth extraction; (**c**) natural bone resorption process after tooth removal; (**d**) guided bone regeneration due to separation of cavity from epithelial cells. A great threat to successful bone regeneration is followed by implantation, fixation, and osseointegration in microbial infection, which may lead to various dental diseases and inflammation. Figure 12 shows possible pathways of the GBR procedure and the role of biofilm formation. Firstly, microbes present in the oral cavity may lead to caries and tooth loss (a). After tooth extraction, two possible modes of action may be undertaken. The most promising method is to perform the GBR procedure using bioactive membranes with dual modes of action, namely creating proper space for bone formation with osteoblast stimulation as well as antibacterial activity and biofilm formation prevention. Such attitude may lead to successful implant fixation and osseointegration. Without any additional activities, the socket can be filled with epithelial cells with complete bone loss, enabling implant fixation (c). Another option is to perform GBR, rebuild resorbed tissue, and perform implantation using standard, e.g., collagen-based membranes. However, without proper prevention during the recovery process and insufficient hygiene, biofilm may be formed, leading to dental diseases (d). Tables 3 and 4 show the results of the antibacterial properties studied against two bacteria strains, namely e. coli and s. aureus. As can be seen, in contrast to standard physiochemical properties, the chemical composition of membranes had a crucial effect on bacteria division and the number of colonies forming units (CFU). In both cases (bacteria gram (\(-\)) and (\(+\))), samples 1-4 did not exhibit sufficient antibacterial activity to reduce the number of CFU. On the contrary, samples 5 and 6, which contained higher amounts of periclase nanoparticles, exhibited a hampering effect on bacteria multiplication. Importantly, in both cases, a bacteriostatic effect was observed after 2 h of incubation; after this period, it slightly weakened, and after 6 h or longer, an antibacterial effect was observed. Of note, higher antibacterial efficiency was observed for gram-negative bacteria, which can be attributed to the thinner cell walls and lower content of murein. Although antibacterial activity increased along with MgO content, samples containing a higher amount of periclase were characterized by low homogeneity and some agglomerates, resulting in overall material quality. Moreover, an MgO content of around 10% caused a significant culture medium increase (up to 8.4), which had a negative impact on cell viability. Figure 11: Swelling degree of samples 1–6.