## 1 Introduction  
Bone substitute materials can be categorized into four groups depending on their origin: autologous from the same subject, allogenic from another individual within the same species, xenogeneic from another species, and alloplastic that are synthetically produced [1]. Autologous bone contains both active bone cells and growth factors that can promote bone regeneration [2], but its use in clinical practice is limited due to post-operative morbidity from graft infections and/or neurologic risks related to bone harvesting in intra-oral sites [3]. Allografts and xenografts are osteeconductive but not osteoinductive [4; 5], unlike other xenograft equine-derived biomaterials. They are used successfully in several fields of oral surgery [6; 7; 8; 9; 10; 11; 12; 13; 14] and should be preferred for being resistant to prion infections (i.e., Bovine Spongiform Encephalopathies) [15; 16]. Moreover, nonantigenic equine bone retains type I collagen, along with a cellular matrix that contains a high amount of growth factors such IGF II, TGF-beta, IGF I, PDGF, bFGF, and BMPs [17]. Many vitro studies show the positive effects of collagen in the production of new bone [7; 18; 19; 20]. Equine bone substitute blocks may represent an alternative to particulate grafting materials for many types of augmentation procedures, since it ensures a source of osteoinductive growth factors and a rigid structure for mechanical support [21; 22; 23; 24]. In other studies, the resorption rates reported confirmed the excellent volumetric stability and great flexibility of autologous bone blocks in all clinical situations, despite intra- and post-operative complications [25; 26; 27; 28]. Particulate xenogeneic bone substitutes in combination with collagen membranes are indicated for deficient ridge contour augmentation but, due to their mechanical instability, need a rigid membrane to obtain three-dimensional augmentation [29; 30]. The use of xenogeneic bone blocks allows clinicians to overcome the poor three-dimensional stability of particulate substitutes without the necessity of a rigid membrane, providing good long-term results [2; 31]. The bone blocks provided in cubic or parallelepiped shape do not usually match the three-dimensionality of the bone defects, resulting in the necessity to model the blocks [32]. The shaping can be performed before or during the surgery. Should the clinician provide a Cone Beam Computed Tomography (CBCT) prior to surgery, the industry can send a preshaped and sterilized bone graft. Alternatively, the clinician can shape the bone block intra- or peri-operatively by hand, or by using a numerical control milling machine (CNC). Hand shaping could be performed with rotating instruments or vibrating instruments. Rotating instruments, mounted on high-speed or low-speed devices, use burs for different materials and shapes to perform an osteotomy, and vibrating instruments are divided into piezoelectric instruments and sonic instruments. Piezoelectric instruments exploit the dimensional deformation of piezoceramic disks subjected to the switch of the electric charge to make a tip vibrate. The tips could be different in shape and material, with a precise indication for each. An osteotomy is performed with bone micromization that is produced by mechanical shockwaves, with a linear vibration ranging from 24 to 36 kHz and an amplitude varying from 20 to 200 mm. The main features of this device are represented by a micrometric cut, namely the selective activity on the mineralized tissues and the positive influence of the ultrasonic cut on bone healing [33]. The air-driven sonic osteetome performs an osteotomy with a vibration ranging from 3 to 6 kHz and an amplitude varying from 200 to 300 mm. Sonic tips rotate with a circular tapping motion and are oriented by the friction into the osteotomy line [34]. The cutting action that causes bone trauma may produce carbonization and debris, which may interfere with the healing response in all surgical procedures.