## 4 Discussion
In all evaluated groups, both microtomography and histology revealed a trend of increasing new bone formation between 4 and 8 weeks, accompanied by a decrease in residual graft material, indicating its resorption potential. The histological images of the AESO-based membrane, compared to traditional collagen membranes, revealed significant advantages, particularly in terms of resorption rate. Experimental studies have shown that lyophilized porcine collagen membranes from various brands undergo rapid resorption within 30 days [29], which may compromise their stability and limit their ability to maintain the necessary space for bone regeneration during the healing process [31]. Although collagen membranes offer bioactive advantages, such as low immunogenicity, attraction of reparative cells, and high vascularization, their rapid degradation, particularly in the case of type I collagen membranes, can impair the maintenance of the bone volume required for complete defect filling [29]. In contrast, the 3D printed membrane developed in this study, with controlled and prolonged absorption beyond 8 weeks, as evaluated in photomicrographs, provides durable mechanical support, which is essential for graft stability and predictability in bone regeneration, resembling for these functions non-resorbable barriers such as expanded polytetrafluoroethylene (e-PTFE) [32]. Thus, the customized membrane not only surpasses collagen membranes in terms of structural stability but also offers greater potential for long-term regenerative outcomes, especially in the presence of defects requiring extended remodeling periods, as described by [PERSON] et al., 2017 [33]. In a comparative study investigating the use of autogenous grafts with or without a non-resorbable rigid membrane [31], the results for the group that used a graft with a non-resorbable membrane were similar to those in this study. Specifically, the reported mean bone formation was 22% \(\pm\) 7.9% after 45 days, compared to a mean of 5.68% \(\pm\) 2.02% at 4 weeks and 16.53% \(\pm\) 6.43% at 8 weeks in this study, following a similar pattern of centripetal bone formation. The centripetal bone formation observed in this and other studies may be related to the regeneration initiated at the edges of the defect, where there is a greater availability of osteoprogenitor cells and growth factors, which are enhanced by the use of grafts and membranes. This pattern also reflects the vascularization process, which progresses from the periphery to the center of the defect. Additionally, biomaterial resorption directly influences this dynamic, as slow-resorbing materials such as GTO act as osteoconductive scaffolds, facilitating a gradual bone deposition. Although the biomaterial and membrane support bone regeneration, the progression of bone formation still follows a natural biological dynamic influenced by vascularization and cellular recruitment. Despite the challenges associated with stabilizing dome-shaped membranes, this configuration offers significant benefits for guided bone regeneration (GBR). Previous studies indicate that the three-dimensional curved conformation improves space maintenance, which is essential for bone formation without soft tissue invasion, while potentially distributing mechanical forces more efficiently at the defect site, minimizing the risk of membrane collapse [34]. The lower bone formation observed in our study may be attributed to a key limitation: the difficulty in achieving stable fixation of the AESO-based membrane over the bone defect. Despite its diameter exceeding that of the defect, the membrane exhibited some degree of mobility, which may have impacted the stability of the bone substitute and the preservation of the necessary space for effective tissue regeneration [35]. Nevertheless, the results indicate that the AESO-based membrane has promising potential for clinical applications in maxillofacial and dental surgeries requiring guided bone regeneration (GBR).