## 1 Introduction  
Guided bone regeneration also known as GBR has been a challenge in oral and implant surgery for the past thirty years. Many different surgical techniques and devices have been used in the attempt to reconstruct resorbed edentulous ridges. The literature in the field is scarce due to the difficulty in recruiting the right group of patients in order to perform randomized controlled clinical trials (RCT) on such lesions; therefore, the judgement of the international community is based on case reports and retrospective studies [1, 2, 3]. The principles of GBR are based on the use of a material protecting a bone graft or a mix of bone and biomaterials, in order to isolate the blood clot and the graft from the ingrowth of the soft tissue, and thus favoring angiogenesis within the protected bone graft leading to the regeneration of new vital bone [4, 5, 6]. In the last decade a new product was introduced in the clinical community that proved to be successful and predictable on top of showing a very low morbidity. A membrane made of xenogeneic collagenated bone with features that are very different from any other material used in the past, the bone lamina is produced in different shapes and thicknesses covering most of the needed surgical options [7, 8, 9]. The bone lamina has also been used successfully in other cranial applications such as the reconstruction of the orbital floor and the reparation of the sinus wall combined with zygomatic implants [10, 11, 12]. The most important advantage of the bone lamina technique is its reaction to exposure to the oral environment. When GBR first surfaced in the 1990s, the only barrier available was made of polytetrafluoroethylene expanded (PTFE), and this proved to be effective but also prone to complications. When soft tissue would not protect it for the time needed, the membrane was then modified, adding a titanium skeleton that would enhance the 'dome' effect for bone regeneration. An early exposure of the membrane would often compromise the final result [13; 14; 15]. In 2011 a classification of the complications related to the use of non-resorbable membranes in GBR procedures was published. The classification reported seven different types of complications: four in the healing period and three surgical [16]. A recent publication in 2019 reported the management of 80 complications in vertical and horizontal ridge augmentation cases treated with d-PTFE: 70% of complications appeared before 2 months after surgery, 43.75% of complications were in the anterior maxilla and 20% were in the lower left mandible [17]. These complications forced researchers to look for a resorbable alternative to PTFE and d-PTFE, and different types of materials were offered in the market. Resorbable membranes are effective and powerful for horizontal defects, while they are more difficult to use for vertical defects and need to be stabilized with pins or nails, and their resorption time is variable [2; 18]. For these reasons, a membrane that can be stiff, is easy to adapt to defects and does not cause complications when exposed would appear to be very appealing to clinicians. Bone lamina is produced in different thicknesses, 0.2-0.5-0.9, fitting well with most of the defects needed to be treated with horizontal augmentation, and also in vertical cases where the anatomy is favorable. In the unfortunate event when the lamina becomes exposed, the saliva enzymes simply cause its hydrolyzation, and soft tissue usually granulates on top of the area causing little or no damage to the process of regeneration [19]. To prevent the problems related to d-PTFE and resorbable membranes (exposure, not sufficient stiffness for vertical cases, early resorption), titanium customized meshes have also been introduced for the treatment of tridimensional defects. The results of an RCT comparing vertical ridge augmentation (VRA) with Ti-reinforced d-PTFE to Ti-meshes and collagen membranes showed no differences between the two approaches with similar patterns of bone resorption one year after treatment [20].