The characteristic feature of periodontitis is a loss of the connective tissue and alveeolar structure,termed a loss of attachment.Gingival inflammation is a common concurrent feature.This loss will be evidenced by an apical migration of the junctional epithelium,which can result in a periodontal pocket that coincides with that apical migration.Gingivitis is usually a precursor to periodontitis,but not all gingivitis progresses to periodontitis.Periodontitis results from a host response to microbial plaque;however.mechanisms for its initiation and progression are still being studied.

    Three models have been proposed to expain the progression of periodontitis.The term of periodontal disease activity refers to the stages of the disease characterized by loss of periodontal attachment.It implies that the natural history of periodontal diseasehas periods of active destruction and periods of relative inactivity,although chronic inflammation persists.Caton summarizes the three theories of periodontal disease activity as:1,the continuous paradigms that implies a slow.constant progression of periodontal degeneration;2,the random burst theory that implies that short periods of destruction are followed by periods of no destruction,occurring randomly;and 3,the asynchronous multiple burst theory that implies that periodontal disease activity,and resultant destruction,occurs within a specific period of life and is followed by remission.

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