## 4 Discussion
This is vital for facilitating the transport of essential nutrients to cells, the exchange of nutrients and waste products, and the cellular migration necessary for the bone regeneration process [1; 3; 30]. The scaffold's porosity is a crucial factor for promoting cell infiltration, nutrient exchange, and vascularization, which are fundamental to the success of bone tissue engineering. However, excessive porosity can have negative consequences. For example, high porosity compromises the material's mechanical strength, making the scaffold more fragile and prone to failure, as shown by [PERSON] et al. (2007) [35]. This is especially problematic in load-bearing areas, such as the mandible [3; 30; 35]. There is a consensus that a scaffold porosity of over 50% can promote vascularization [3]. However, too large or numerous pores can hinder cell adhesion, reducing cell density and limiting tissue regeneration. Vascular can also be impaired, as excessive porosity makes it more difficult to form stable vascular networks [3; 30; 44]. Another important point is that scaffolds with high porosity can be challenging to handle during implantation, as they may lose their shape or collapse under their own weight. Additionally, osteoconductivity can be compromised if porosity is not adequately controlled, preventing the adhesion and proliferation of bone cells. Therefore, it is crucial to balance porosity to ensure the scaffold's effectiveness in bone regeneration [35]. The data show that scaffolds with high porosity (e.g., 70%) [31; 35; 36] promote greater bone formation, accompanied by significant vascular invasion and bone regeneration within the pores. [PERSON] et al. (2022) [36] evaluated the masset as a natural bioreactor for \(\beta\)-TCP scaffolds (porosity = 70.6% \(\pm\) 1.8%) or PCL/\(\beta\)-TCP scaffolds (porosity = 50%) in terms of bone regeneration. The study also investigated the effects of pedicle preservation and the isolated or combined application of mesenchymal stem cells (MSCs) or rhBMP2 on the scaffolds. After 12 weeks, a histological analysis revealed that all \(\beta\)-TCP scaffold groups (higher porosity) showed significantly higher rates of new bone formation, regardless of being subjected to a pedicled or non-pedicled surgical approach, compared to parallel groups with \(\beta\)-TCP/PCL scaffolds (lower porosity) (\(p\leq 0.05\)). According to [PERSON] et al. (2022) [32], lower porosity (e.g., 40%) allowed for fragmented physiological bone regeneration. Despite the continuous formation of new physiological tissues being observed throughout the volume of the critical bone defect, the authors [32] correlated the fragmentation of this tissue with the slow biodegradation of the bioceramic, as approximately 40% of the bone defect volume remained occupied by the ceramic after 12 months. Therefore, this suggests that porosity is not the sole factor influencing regenerative capacity, and that other factors, such as material composition, also impact the results [32; 36]. [PERSON] et al. (2017) [31] also reported that scaffolds with different levels of porosity (PTMC-CaP vs. \(\beta\)-TCP) affected the amount of new bone formed. Due to the 70% porosity in the PTMC-CaP scaffolds, the concentration of CaP particles in the matrices is reduced to only 9%, which is insufficient to generate significant bioactivity. This low concentration explains the reduced new bone formation in these scaffolds compared to the \(\beta\)-TCP scaffolds, which have 60% porosity [31]. [PERSON] et al. (2021) [26] demonstrated that scaffolds with higher porosity (TCP) (74,2% \(\pm\) 2,2%) and larger pores (365 \(\pm\) 30 \(\upmu\)m) maintained better structure, while PLGA/TCP (63,7% \(\pm\) 4,0%) (345 \(\pm\) 10 \(\upmu\)m) scaffolds exhibited lower peripheral bone density. Furthermore, the compressive strengths of the PLGA/TCP scaffolds were substantially lower (0.7 \(\pm\) 0.06 MPa) than those of the TCP scaffolds (20.56 \(\pm\) 1.81 MPa). [PERSON] et al.