## 4 Discussion
Referring to the systematic review and meta-analysis from the [PERSON] et al. group [25], it seems that xenograft materials should be considered among the best available graft materials for preserving the alveolar process after tooth extraction. A 5-year study conducted by [PERSON] et al. [26] found that sufficient quality and volume of bone allows for the predictable placement of implants in the maxillary sinus augmented with bovine bone grafts. Various combinations of biomaterial combinations have been described in the literature to maximize the advantage and minimize the disadvantage of the biomaterials described above. As an example, allogeneic bone can successfully be used in combination with xenografts for guided bone regeneration (GBR) in bone augmentation procedures as described by the [PERSON] group for the technique known by the common name \"the sausage technique\" where a particulated autogenous bone with an organic bovine bone-derived mineral is used [27; 28]. The literature also describes the possible use of bovine xenogeneic bone in GBR combined with blood derivates such as platelet-rich plasma (PRP), platelet-rich fibrin (PRF), and concentrated growth factors CGF are used in various days of dentistry to promote healing and their combination with bone graft particles is known colloquially as a sticky bone [23; 29; 30]. The use of xenogeneic bone to graft increases the width of the alveolar process when used in lateral augmentation [31]. [PERSON] et al. found that lateral ridge augmentation procedures with implant placement can maintain peri-implant health over time [32]. [PERSON] et al. [33], in a 5-year follow-up, demonstrated that dehisced implants, if treated with GBR (membrane + grafting material), may lead to a survival rate of implants similar to that obtained in implants completely embedded in native bone. [PERSON] et al. [34], in the latest systematic review and meta-analysis, have found that reconstructive surgical correction of peri-implant dehiscences and fenestrations with GBR is associated with a lower probability of implant dehiscences and fenestrations persistence when compared to a repositioning of a full-thickness flap without use of reconstructive techniques. The application of the xenogeneic bone material and a xenogeneic collagen membrane is considered to be a recommended, well-documented and widely used dental surgical procedure [35; 36]. We have found no statistically significant differences in MBL between no GBR G1 and GBR G2; moreover, even after excluding cases of peri-implantitis, still no significant differences were observed between the groups, and the nominal differences between the groups were even smaller. Taking into account the characteristics of the material, it seems reasonable to recommend xenogeneic bone in the case of the treatment of small peri-implant bone defects such as dehiscence. In our material, the incidence of peri-implantitis complications was assessed, and a total of 5.3% of patients were diagnosed with peri-implantitis. Peri-implantitis is an inflammatory process that affects both the hard and soft tissues that surround dental implants. This condition is caused by a polymicrobial aggressive biofilm that colonizes the implant and abutment surface at the peri-implant crevice level [37]. According to [PERSON] et al. [38], as stated in a systematic review and meta-analysis, the mean prevalence of peri-implantitis is 19.53% at the patient level. [PERSON] et al., in a 9-year observational study of randomly selected 588 patients of the Swedish population, observed 45% of all patients with peri-implantitis (bleeding on probing/supputation and bone loss > 0.5 mm) and a moderate/severe peri-implantitis (bleeding on probing/supputation and bone loss > 2 mm) was diagnosed in 14.5% of patients and bone loss > 2 mm) [39]. However, the reports of the prevalence of peri-implant mucositis and peri-implantitis range are relatively wide and can be dependent on the study population, as [PERSON] et al.