Gingival response to orthodontic force

Orthodontic tooth movement is brought about by prolonged application of for ce on the attachment apparatus. This results in cellular and extracellular changes within the periodontium. As shown in numerous studies, tooth moveme nt is achieved after the remodeling of alveolar bone and the response of th e periodontal ligament to the mechanical force. Although gingival changes h ave also been found to be an important factor in the overall response, the effect of orthodontic tooth movement on the gingiva has been investigated t o a lesser extent. Unlike bone and periodontal ligament, which regain their original structure after removal of force, the gingival tissue does not re gain its pretreatment structure, a fact on which a hypothesis has been made that tooth relapse after removal of retention may be associated with chang es in the gingiva. The present review summarizes available data on the effe ct of orthodontic force on collagen, elastin, and collagenase in the gingiv a and its relevance to understanding the mechanism of tooth relapse.