Periodontitis is an inflammatory disease which is involved with gingival attachment loss and an alveolar bone resorption. Traditional methods for taking X-ray photograph or assessments of probing depth and clinical attachment level are provided the previous periodontal tissue breakdown, however, these methods are hard to confirm the disease activity and predict of the disease outcome. Therefore, the component or quality of gingival crevicular fluid (GCF), which is directly, reflects the gingival inflammation is noticed. It firstly describes that GCF containing the inflammatory mediator, cytokine, and bone markers are not only related to the bone resorption but also affected the periodontal disease activity. As the final part in the series it lastly discusses the possible uses of predictive diagnostic tests of periodontal disease activity in dental practice.