Molecular basis for immunohistochemical and inflammatory changes during progression of gingivitis to periodontitis

Two common diseases – gingivitis and periodontitis – affect the periodontium. Symptoms of disease entities are used for distinguishing various forms of gingivitis and periodontitis. Gingivitis follows a linear and progressive course when a healthy individual stops oral care, as shown by the experimental gingivitis model. It is not known if and when gingivitis transforms into periodontitis. A very limited number of studies present direct evidence regarding the histological changes over time and how they correlate to the clinical transition from gingivitis to periodontitis. This review focuses on the pathological changes that occur during the progression of gingivitis into periodontitis through discussing the molecular, cellular and immunohistochemical aspects of the inflammatory process. Molecular pathways regulating periodontal inflammation also determine the outcomes of disease and healing. Treatment of inflammatory diseases, particularly periodontitis in which extensive tissue damage could result from the inflammatory process, needs to target full restoration of the lost tissues. This can only be accomplished by a thorough understanding of the activation and resolution of periodontal disease and of the molecular events that occur during these phases.