The ability of bone to induce new cartilage and bone formation is from the action of the BMPs. Inorganic matrix: It constitutes for 60-70% of dry weight of bone i.e. 2/3 of matrix. The inorganic matter is composed principally of minerals calcium, phosphate along with hydroxyl, carbonates, citrate and trace amount of other ions, such as sodium, magnesium, and fluorine. They form hydroxyl apatite crystals Ca10 (PO4)6(OH) 2. These apatite crystals are arranged parallel to the long axes of collagen fibers and appear to be deposited on and within these fibers. In this fashion the bone can withstand the heavy mechanical stresses applied to it during function. REMODELING AND REPAIR OF BONE: In normal physiology, there is a coupling of resorption and formation in the bone remodeling sequence. In the various metabolic bone diseases, there are abnormalities in the coordinated activity of the osteoclastic and osteoblastic cells. Likewise, in a pathological state such as inflammation, there is an uncoupling of these activities resulting in a net loss of bone. A complex cascade of events involving a host of autocrine and paracrine factors is involved in the regulation of bone metabolism.
The structure of alveolar bone proper varies on different sides of tooth, with different functional demands. Under physiologic conditions teeth migrate continuously in mesial direction toward the midline. This is called physiologic mesial drift. The migration leads to resorption on mesial side and new bone formation on tension side i.e., distal side. Some portions of bone surface may be covered by a thin layer old new bone that anchors short sharpey’s fibers. This new bone is formed during relatively brief periods of bone deposition, which allows the root to remain