## 1 Introduction  
Implant-prosthetic treatment of edentulous patients has now become a therapeutic approach with reliable functional and aesthetic results [1]. Specialists in implantology face high requirements and expectations of patients on the rehabilitation of functions and aesthetics, while an increased share of implant sites are affected by alveolar bone resorption. At the level of the mandibular areas, the insertion of short or small diameter dental implants at the level of the implant sites with severe resorption does not allow for the adequate reconstruction of the alveolar ridge volume and morphology and reduces the success rate of implant-prosthetic restorations [2]. A functional and stable prosthetic implant-mandibular restoration with bone resorption can be compromised in the long term due to the shape and orientation of the residual alveolar bone, improper intermaximillary relationships, and the presence of the inferior mandibular nerve. Implantology and alveolar bone regeneration have always been intertwined fields [3]. Bone regeneration involves histological, morphological, and biological processes induced by both local and recruited cells in association with inflammatory processes, and the formation of the fibrous tissue and bony callus [3]. Today, the alveolar ridge reconstruction is a procedure used in one in four implant sites [4]. It is estimated that up to 50% of all implant procedures performed in the coming years will involve the use of bone grafts [5]. In this context, the reconstruction of the implant sites through the various guided bone regeneration techniques is an important stage of the implant-prosthetic treatment to restore the aesthetic parameters and the optimal functioning of the stomatognathic system [6; 7]. In the case of the resorbed mandibular ridges, the high density and low vascularization of the mandibular cortical bone can impede the efficient alveolar reconstruction and bone tissue regeneration processes [8]. Oral surgeon experience, augmentation technique, and the category of the graft materials are all factors that contribute to the success of the grafting procedure [9]. A wide range of bone regeneration techniques (e.g., guided bone regeneration, distracting osteogenesis, and alveolar ridge division techniques) are used to restore the volume and morphology of the mandibular alveolar ridges [10; 11]. Considering the difficulties related to the maintenance of the stability of the grafted areas affected by severe horizontal and vertical resorptions, Screw-Guided Bone Regeneration (S-GBR) ensures tenting mechanisms that can prevent the collapse of the soft tissues and of bone resorption [12]. S-GBR uses a membrane that delimitates the regenerative bone compartment supported by osteosarcoma screws or dental implants. In our dental practice, we applied the S-GBR technique mostly to patients with anterior and posterior mandibular severe horizontal resorption by using a combination of autogenous bone and xenograft materials, and resorbable collagen membranes. In a recent study with 24 months follow-up, we demonstrated the validity and effectiveness of this technique when used with a bovine-derived xenograft [13]. Despite the numerous studies investigating the alveolar bone augmentation with xenografts of bovine origin, only a few have investigated the predictability and stability of the functional and aesthetic outcome following alveolar bone regeneration procedures with porcine-derived xenografts. A research group has highlighted the fear of patients regarding the possibility of transmitting bovine spongiform encephalopathy (BSE) with degenerative effects in the human brain through xenografts of bovine origin [14]. The risk of foreign body reaction, at intervals of 2 to 10 years, must also be considered for bovine xenografts due to the absence of the biodegradation of the inorganic particles [15].