Abstract
Periodontal tissue destruction is the deterioration of tooth-supporting components, particularly the periodontal ligament (PDL) and alveolar bone, resulting in gingival recession, root exposure, tooth mobility and drifting, and, finally, tooth loss. The breakdown of the epithelial barriers by infection or mechanical damage allows bacteria and their toxins to enter and stimulates the immune response. The bacteria cause periodontal damage via the cascade of the host reaction which is crucial in the destruction of the connective tissue around the tooth. The OPG/RANKL/RANK system is the key player in bone regulation of periodontal tissue and was controlled by both immune and non-immune cells. This knowledge has predicated the successfulness of implant and orthodontics treatments with the predictable healing and regeneration of the bone and supporting tissues surrounding the teeth.