# Clinical Case Employing Two Different Biomaterials in Bone Regeneration
## 1 Introduction  
Mandibular augmentations are surgical procedures that often require the use of bone grafts. This way, after a period of recovery to enable osteointegration, correct implant positioning is possible. In general, they are more complicated than maxillary-bone augmentations because of the thicker cortical layer of the patient's residual bone, which limits blood supply and overall graft integration. The gold-standard approach involves autologous (cortical and medullar) bone harvested from the patient [1, 2]. This ensures limited probability of rejection [3], but still carries inherent risks, particularly with regard to the comorbidity of the harvest site. In general, this grafting technique relies on two major concepts: the \"diamond\" (or regenerative pentagon) and the \"organic room\" [4]. The resulting protocol, which is very common and effective in orthopedic practice, entails that all biological activities occurring during osteointegration are confined to a vital, aseptic, mechanically stable, sealed environment (the \"room\") [4]. Of course, such an environment is difficult to prepare in a more _hostile_ region like the oral. Indeed, surgeons usually have to operate under local anesthesia in a much more contaminated environment. Moreover, application sites are often less surgically accessible, are in contact with moving structures (e.g., the jaw, tongue, and cheeks), and the soft tissue at the sites can be fragile and difficult to utilize for the proper coverage and final sealing of the hypothetical organic room (tissue expanders are, in fact, seldom used in this kind of surgery). This leads to a long postoperative period and subsequent reconstruction of bone-regeneration materials that have been under strain from the patient's unavoidable chewing activity. As a matter of fact, an appropriateorganic room, comparable to the ones used in orthopedic surgery, is very hard to obtain in dental applications. Moreover, the use of autologous bone inevitably entails that a second active operative site is necessary for the harvest, which might increase the possibility of clinical complications. Alternatively, the use of nonautologous bone substitutes (e.g., allografts, xenografts, or synthetic grafts) is highly consolidated through routine practice and clinical results from the literature [5; 6; 7; 8]. Although gaining full control over these materials' characteristics is not trivial, and complex strategies have to be developed [9; 10; 11; 12; 13]. Nonetheless, they are able to provide mechanical properties, microstructures (e.g., porosity [14]), and compositions that are comparable to those of autologous bone [15; 16; 17; 18]. The application protocol might also depend on the chosen biomaterial, and it may be different from the one described above. Nevertheless, the efficacy of these materials for treating any kind of defect is highly documented in the literature [6; 19]. In general, xenografts have applications in defects where mechanical stability is a major requirement. On the other hand, bioactive glasses have a long track record of clinical success in four-wall defects (e.g., socket preservation, sinus lifts), where appropriate filling for a cavity is the main necessity [20]. Although many cases are performed each year, there is still little focus on studying an effective comparison of different biomaterials [21; 22]. Indeed, not all biomaterials exhibit the same behavior in equivalent clinical situations. Moreover, they often have a specific application protocol that might be more or less invasive depending on the application site. Each rehabilitation case might be better treated with a specific biomaterial that best suits the conditions of the defect. Of course, this approach requires a detailed understanding of the features and performance of each graft, and a fair and effective comparison. In this respect, it is clear that the application site's characteristics and a patient's clinical conditions are two major sources of variability in evaluating a material's performance.