**3. Physiological bone regeneration**

Bone modeling is a specialized process wherein old bones are removed from one location and replaced by new bone at a distinct location. This process defines the ultimate shape and size of the skeleton [28]. While bone remodeling is a characteristic process in the mature skeleton that is marked by constant bone restoration via a frequent exchange of aged bone with the fresh one at the same site. The process results in the comprehensive regeneration of mature skeleton in an adult every 10 years [29]. The body tries to sustain the balance between bone formation and elimination during the process of bone remodeling. It takes place in discrete sites called basic multicellular units (BMU). The process initiates by activation phase where an initiating signal (e.g., mechanical strain on the bone, fracture healing, etc.) flags the requirement of the remodeling process [30]. After the activation, the commencement of the resorptive phase occurs, wherein osteoclasts depletes bone by proteolytic degradation and acidification. Osteoblasts travel to the eroded space and begin the ossification after the stimulation of transcription factors that encourages the bone formation [31]. Ossified bone is subsequently mineralized and eventually remodeling cycle ends.
