Biology and principles of periodontal wound healing/regeneration.

The native periodontium includes cementum, a functionally oriented periodontal ligament, alveolar bone and gingiva. Pathologic and/or traumatic events may lead to the loss or damage of this anatomical structure. Since the 1970s, a number of procedures have been investigated in an attempt to restore such lost tissues. Numerous clinical trials have shown positive outcomes for various reconstructive surgical protocols. Reduced probing depths, clinical attachment gain, and radiographic bone fill have been reported extensively for intrabony and furcation defects following scaling and root planing, open flap debridement, autogenous bone grafting, implantation of biomaterials including bone derivatives and bone substitutes, guided-tissue regeneration (GTR) procedures, and implantation of biologic factors, including enamel matrix proteins. Histological studies have shown that various surgical periodontal procedures can lead to different patterns of healing. Healing by formation of a long junctional epithelium (epithelial attachment) is characterized by a thin epithelium extending apically interposed between the root surface and the gingival connective tissue (4, 23). Connective tissue repair (new attachment) is represented by collagen fibers oriented parallel or perpendicular to a root surface previously exposed to periodontal disease or otherwise deprived of its periodontal attachment. In contrast, periodontal regeneration is characterized by de novo formation of cementum, a functionally oriented periodontal ligament, alveolar bone, and gingiva (restitutio ad integrum). Nevertheless, it would be naive to expect these to occur as distinctly separate biologic outcomes following reconstruction of the periodontal attachment. For example, periodontal regeneration should be expected to include elements of a new, as well as an epithelial, attachment. Predictability of outcomes following surgical procedures is of fundamental importance in medicine. As periodontal-regenerative procedures are time consuming and financially demanding, there is increasing interest by clinicians to learn of factors that may influence the clinical outcome following periodontal reconstructive surgery in order to provide the best possible service to patients. This goal can only be achieved if biological aspects of wound healing and regeneration are taken into consideration. The objectives of the present article are to provide an overview of wound healing following periodontal surgical procedures, to discuss the basic principles of periodontal regeneration, and to illustrate the factors that influence this process.