## 4 Discussion

Table 3: Relationship between augmentation technique and bone graft resorption variable. adopt the shell technique is to obtain significantly less bone volume loss in the CS group, compared with the GBR group. Numerous bone defects, such as horizontal and vertical bone augmentation [15], cleft lip and palate [16], and maxillary sinus augmentation [17; 18], can be reconstructed successfully with allogeneic bone grafting. Many studies have confirmed the use of allogeneic grafting in particulate and block forms. However, few studies focused on the effectiveness of allogeneic block application using the shell technique [18]. In the present study, the effectiveness of the shell technique performed with the help of allogeneic block graft was evaluated, and a volume loss of 8.26 \(\pm\) 1.60% was observed after 7-month recovery period. In the literature, numerous horizontal bone augmentation techniques have been reported with varying success rates. [PERSON] et al. reconstructed a hard tissue deficient region by mixing autogenous bone and xenograft particles at a ratio of 1:1 and covering with a resorbable membrane using pins. In this technique, the benefits of osteogenic and osteoinductive properties of autogenous bone occur. Additionally, the osteoconductive structure of xenografts is used in an attempt to prevent unpredictable resorption, which can be seen in autogenous bone. In the present study, autogenous and xenograft particles in a ratio of 1:1 were utilized as graft material in both groups [19]. There are four major principles to accomplish successful GBR, which are described by [PERSON] et al. as PASS: primary closure of wound area, angiogenesis to accelerate new bone formation, space creation to avoid the collapse of bone grafts, and stability of the blood clot. Such requirements reduce the incidence of adverse effects and enable better results [20]. Autogenous block grafts have been widely and extensively used for many years to create a space and maintain sufficient stability in it until the bone graft is integrated with the host bone. Since autogenous blocks can be used on their own, they are fixed to the recipient area using the shell technique. Subsequently, the created space is filled with bone graft particulates [21]. In a published systemic review, a comparable amount of regenerative bone was obtained using either allogenic graft or autogenous block graft [22]. In the literature, there are many studies in which autogenous or allogeneic blocks are applied alone for hard tissue augmentation, but they have shown varying amounts of resorption. [PERSON] et al. have applied alleogenous block grafts alone in the mandible for hard tissue augmentation. As a result, 31% resorption was observed following a 6-month healing period after dental implantation, with an additional 10% resorption 1 year after implant loading [23], whereas [PERSON] et al. observed an average of 43.7% resorption of the autogenous block grafts used in horizontal augmentation after a 12-month follow-up [24]. [PERSON] et al. also reported an average of 25.4% resorption of autogenous block grafts 4-6 months after the procedure [25]. The possible reason proposed for the higher rate of resorption observed in studies where only autogenous and block allografts were applied for horizontal hard tissue augmentation, in comparison to the present study, is the role of the xenograft particulates which filled the space that was created between the fixed block allograft material and the recipient site in the augmented region and performed using the shell technique. Apart from the disadvantages of autogenous block augmentation, such as the difficulty of harvesting autogenous block graft, the inability to obtain the desired amount in some cases, and the risk of nerve damage and patient morbidity; the excess amount of resorption is also encountered, which has provoked the question of whether it is possible for allogeneic grafts to be an alternative to autogenous blocks. [PERSON] et al.