Diagrammatic Representation of Resorption Dynamics at the Biochemical Level.

The bone/root resorption process is similar at cellular levels for both osteoclasts and odontoclasts.⁸ Cellular differentiation from mononucleated (progenitor osteoclasts) to multinucleated (mature osteoclasts) involves pro-resorption and anti-resorption. The M-CSF is responsible for proliferation and differentiation of progenitor cells; proinflammatory cytokines are directly responsible for differentiation and activation of pre-osteoclasts, or activation of RANKL, which in turn leads to pro-resorptive gene expression (TRAP, etc.). Anti-resorptive OPG (decoy receptor for RANKL) and IL-1RA (receptor antagonist to IL-1β) govern the resorptive activity, with the RANKL/OPG ratio being the primary governing factor.

IL-1β, interleukin-1β; IL-1RA, interleukin-1 receptor antagonist; IL-6, interleukin 6; M-CSF, macrophage colony-stimulating factor; OPG, osteoprotegerin; PDL, periodontal ligament; RANKL, receptor activator of nuclear factor kappa-B ligand; TNF-α, tumor necrosis factor-α; TRAP, tartrate-resistant acid phosphatase.