# SEM and FT-MIR Analysis of Human Demineralized Dentin Matrix: An In Vitro Study
## 1 Introduction  
After tooth extraction, hard and soft tissue withstand remodeling processes. Alveolar ridge undergoes resorption, mostly in the horizontal but also in the vertical dimension [1]. Several studies analyzed the changes after tooth extraction [2]. The majority of horizontal and vertical changes take place during the first 3-6 months after tooth extraction and continue through the first year [3]. In fact, the horizontal bone loss is higher on the buccal side of the alveolar ridge than on the lingual/palatal side. On the other hand, the vertical resorption is minor and mainly on the buccal aspect of the alveolar ridge. This volumetric contraction of the alveolar ridge may jeopardize an appropriate implant-supported prosthetic rehabilitation. Several surgical techniques have been developed to reduce or, at least, minimize the changes of soft and hard tissue following tooth loss. The main alveolar ridge preservation techniques concern on soft-tissue preservation, hard-tissue preservation (guided bone regeneration) and the combination of soft tissue and hard tissue preservation (socket seal technique) [4]. Moreover, different regenerative techniques have been tested: the use of bone grafts alone; barrier membranes alone, either resorbable or not; the combination of barrier membranes and bone graft. Metanalyses have shown that alveolar ridge preservation techniques are effective in significantly reducing vertical and horizontal alveolar ridge contraction [5; 6]. Also [PERSON] et al. [7] reported positive results in the use of bone grafting and resorbable membrane compared with spontaneous healing. Autologous bonerepresents the ideal graft material due to its osteeoinductive and osteeconductive properties [8]. Nevertheless, its limits are the small amount of bone graft available, the morbidity of the donor area, and the risk of resorption of the bone graft itself. The research has led to developing alternatives, such as allogenic grafts, alloplastic grafts, and xenogenic grafts [9]. In the past decades, the use of demineralized dentin matrix (DDM) as a potential bone substitute has been proposed. Dentin consists of (i) 70% inorganic component (hydroxyapatite, tricalcium phosphate, octacalcium phosphate, and amorphous calcium phosphate); (ii) 20% organic component (collagen I 90%, collagen III and V in small quantities, and non-collagen proteins); (iii) 10% water [10]. Its composition is, therefore, similar to that of bone tissue. Dentin also contains various growth factors, such as Fibroblast Growth Factors -2 (FGF-2), transforming growth factors-\(\beta\)1 (TGF-\(\beta\)1), insulin growth factor-1 (IGF-1) and, above all, bone morphogenetic proteins (BMPs) involved in the osteogenesis process [10]. Through demineralization, dentin can release the growth factors [11] and consequently express its osteoinductive and osteeconductive properties [12]. Thereby acting as a scaffold, dentin promotes the formation of bone tissue (osteoconduction), but at the same time, it releases the growth factors that promote the formation of bone (osteoinduction). Moreover, different in vivo studies have reported encouraging results [13; 14; 15] that led to this material being considered as a possible alternative to autologous bone grafts [16]. It has been shown that the preparation procedure, the shape, and the size of the dentin particles can influence dentin's osteoconductive and osteoinductive properties [17]. Excessive demineralization can damage the structure of the dentin and negatively affect the composition and function of growth factors; on the other hand, a reduced demineralization produces a scaffold with osteeconductive and osteoinductive properties [18].