# Role of Autologous Platelet Gel (APG) in Bone Healing: A Rabbit Study
## 1 Introduction  
There is a need to find more efficient surgical procedures and biomaterials for bone regeneration. Biomaterials are available in many different sizes, porosity, and quantity [1], and are utilized for the treatment of bone loss due to tooth extraction or inflammation [2]. If compared to autogenous bone, the substitutes are cell-free and characterized by an increased osteeintegration period and a lower level of biological activity. Nowadays, bone grafts represent a useful alternative option requiring a lower quantity of new bone formation when compared to autogenous bone [3]. Several studies have been published on updates and the improved performance of various types of bone grafts for bone regeneration. Different typologies of materials and methods have been proposed for improving bone healing: Autologous grafts; demineralized and mineralized freeze-dried allografts; anorganic bovine and porcine bone; collagenated substitutes, coralline calcium carbonate; bioglasses; hydroxyapatite; polylaticidepolyglycolide-derivate grafts; synthetic polymers; and calcium sulphate [3]. They are commercially available in the form of particles, cement pastes, gels, and blocks of osteoconductive and osteoinductive biomaterials for boneaugmentation and hard tissue reconstruction. The good qualities of biomaterials are osteoinduction and osteoconduction, and mechanical resistance under functional loads with easy management in clinical practice. Autologous bone is believed to be the \"gold standard\" because it promotes angiogenesis and has osteogenic qualities, and is also osteoinductive, osteoconductive, with no risk of infection transmission [4]. The use of autologous bone is, however, related to some disadvantages, such as higher morbidity and complications related to the management of a donor site and a limited availability of graft [5]. Bone grafts have been proposed for bone augmentation for maintaining space and scaffolding between the bone surface and periosteum/membranes. Many bone graft alternatives and adjuvant, in the form of substitutes and recombinant human growth factors, have been reported in the literature [6]. The use of platelet concentrates is on the increase in clinical practice and are used alone or mixed with biomaterials. [PERSON] et al. (2001) [7], described platelet rich fibrin (L-PRF), which is a second generation platelet concentrate that contains fibrin and platelet. It eases and guides angiogenesis, traps the circulating stem cells [8], and offers wound protection through epithelial coverage [9]. It is obtained after slow polymerization of the fibrinogen and contains cytokines and many growth factors that are released into the wound site over a long period [10]. This fibrin matrix has been used with success for improving bone regeneration in implants in the early healing stages after implant placement [11]. In addition, autologous cancellous bone combined with autologous platelets improved bone healing in an in vivo critical-size cylindrical defect study [12]. Furthermore, the combination collegene 1 and PRP-enhanced bone healing in a critical-size defect in a pig model [13]. Therefore, the utilization of scaffolds for growth factor delivery and cells has drawn a considerable amount of interest in bone augmentation [14]. In recent years, there has been an increased interest in growth factors obtained from autologous platelets and their use. The aim of this study is to evaluate the influence of autologous platelet gel APG on bone healing in a rabbit model.