In this review, most of the known and postulated mechanisms of osteopontin (OPN) and its role in bone remodeling and orthodontic tooth movement are discussed based on available literature. OPN, a multifunctional protein, is considered crucial for bone remodeling, biomineralization, and periodontal remodeling during mechanical tension and stress (orthodontic tooth movement). It contributes to bone remodeling by promoting osteoclastogenesis and osteoclast activity through CD44- and αvβ3-mediated cell signaling. Further, it has a definitive role in bone remodeling by the formation of podosomes, osteoclast survival, and osteoclast motility. OPN has been shown to have a regulatory effect on hydroxyapatite crystal (HAP) growth and potently inhibits the mineralization of osteoblast cultures in a phosphate-dependent manner. Bone remodeling is vital for orthodontic tooth movement. Significant compressive and tensional forces on the periodontium induce the signaling pathways mediated by various osteogenic genes including OPN, bone sialoprotein, Osterix, and osteocalcin. The signaling pathways involved in the regulation of OPN and its effect on the periodontal tissues during orthodontic tooth movement are further discussed in this review. A limited number of studies have suggested the use of OPN as a biomarker to assess orthodontic treatment. Furthermore, the association of single nucleotide polymorphisms (SNPs) in OPN coding gene Spp1 with orthodontically induced root resorption remains largely unexplored. Accordingly, future research directions for OPN are outlined in this review.

Wound healing in human periodontium is a complex process which involves both cell-cell and cell-matrix interactions. Integrins play a major role in regulation of these cell-cell, cell-matrix interaction. Wound healing involves two major events i.e. re-epithelialization and connective tissue repair. In this concise review, we will discuss the role of integrins in these major events as well as their impIications in periodontal wound repair. Integrins are differentially expressed in both of these major events. In re-epithelialization, keratinocytes express novel integrins receptors αvβ1, α5β1and αvβ6 which are not expressed in normal healthy epithelium. Re-epithelialization also involves interaction of integrins with TGF-β and fibronectin. Similarly, in connective tissue repair, the activation of fibroblast as well as the expression of integrins α5β1 and α3β1 is upregulated. In healthy periodontium, integrin αvβ6 is normally expressed in junctional epithelium which is generally expressed only at wound sites in other parts of the body. The epithelialization at implant surface has not been yet fully explored with respect to interactions among integrins and other extra-cellular matrix molecules.

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