Regeneration of periodontal tissues: cementogenesis revisited.

Virtually all types of periodontal disease are caused by periodontal pocket infections, although several other factors, including trauma, aging, systemic diseases, genetics, etc., can contribute to the destruction of the periodontium (1, 18, 31, 52, 60, 107, 128, 127, 194). Repair of the periodontium and the regeneration of periodontal tissues remains a major goal in the treatment of periodontal disease and is an area still in need of major research attention, as recently stated by the American Academy of Periodontology (260). In general, to achieve complete tissue regeneration and repair, it is necessary to recapitulate the process of embryogenesis and morphogenesis involved in the original formation of the tissue. In the case of the periodontium, complete periodontal repair entails de novo cementogenesis, osteogenesis and the formation of periodontal ligament fibers. Current strategies for periodontal repair are based on anti-infectious measures such as scaling and root planing, guided tissue regeneration (with or without bone grafts) or the use of growth factors, none of which fully restore the architecture of the original periodontium. Several different approaches involving tissue engineering are currently being explored to achieve complete, reliable and reproducible regeneration of the periodontium. As tissue engineering is defined as the science that develops techniques (based on principles of cell and developmental biology) for fabricating new tissues to replace or regenerate lost tissues (205), it is important to understand the formation of specific tissues, the physico-chemical characteristics of the tissues and the molecular events leading to the normal function of the tissues.