Need for the study:

Socket preservation is a procedure to preserve hard and soft tissue of the alveolar ridge after extraction. The alveolar process is a tooth dependent structure. extraction of teeth leads to an edentulous space and loss of alveolar bone, function and aesthetics. studies have shown mean reduction of 3.8mm in width and 1.24 mm of height of the alveolar bone in the first six months following extraction. Bone regeneration is a major challenge in reconstructive surgery. Bone substitutes are frequently used in the surgical procedure to augment and regenerate hard tissues. The gold standard for alveolar reconstruction is the autologous bone enhancing osteogenesis, osteoinduction, and osteoconduction. The problem lies in its scarcity, depending on the donor site, and association with several risks like nerve damage, infection, bleeding, scarring and loss of function. Other disadvantages include possible donor site injury, host morbidity, prolonged operation times and cost. Since the first successful bone transplantation carried out in 1668 by van meek’ren, a dutch surgeon, more than 50 bone substitutes have been described in the literature. Unfortunately, none has fulfilled all the requirements to gain wide acceptance in clinical practice. the ideal bone substitute should be biocompatible, osteoinductive or at least osteoconductive, and have satisfactory mechanical properties. This bone should be available in unlimited quantity and at a low cost. Among inorganic materials, calcium salts were the first implants to be successfully used in clinical practice. They present the advantage of mimicking the human mineral bone phase and they do not elicit any immune response as they do not contain living cells or organic matrix. Hydroxyapatite (ha) is the main inorganic constituent of bones and teeth. It is a key material of skeletal tissue; many types of bone graft materials have ha as a basic component. In many disciplines of surgery ha is being used as graft material successfully. In particular, ha shows highest level of bioactivity and forms quick bond with bone. The eggshell formulations are being used since beginning as trace element and mineral supplying agents. The eggshell powder has been examined in rats for bone healing. Few studies show surface modified eggshell powder as osteoconductive bone filling material with variable benefit in bone regeneration.the literature showed material properties of eggshell-derived hydroxyapatite (enha) are superior when compared with the commercially available graft materials. So, the enha has been introduced as bone graft substitute recently. Histomorphometric evaluation showed that the enha has excellent new bone formation ability. This has led to the curiosity to prepare the enha from eggshell waste in a very economical way. Many current socket preservation techniques use barrier membrane for primary closure, but there are often difficulties in adoption of the membrane, and a second surgical procedure is required to remove the membrane. In general, membrane use is time-consuming and expensive.   prf is an autologous source, and it contains various growth factors such as platelet-derived growth factors and insulin-like growth factors.  prf is mostly preferred over other concentrates because it releases the growth factors at a sustained rate over a longer period, thereby optimizing wound healing. The prf membrane acts as a cover for graft material and as a barrier membrane for guided bone regeneration. Therefore, according to the characteristics of eggshell-derived nanohydroxyapatite such as bone healing, bone remodelling and bone regeneration with increased density, as suggested in the literature, in this study we utilize eggshell-derived nanohydroxyapatite along with prf as a barrier membrane to assess pain, wound healing, changes in lamina dura, crestal bone level and bone density in mandibular extraction sockets and compare it with commonly used demineralised freeze dried bone allograft (DFDBA) covered with prf membrane. This study is taken up considering the limitations of allografts and the fact that no study has been undertaken to compare the efficacy of eggshell-derived nanohydroxyapatite with the commonly used demineralised freeze dried bone allograft (DFDBA) in human extraction sockets