It is of concern to both public health agencies and health professionals to know whether the prevalence of periodontal diseases is increasing or decreasing in the world today. Unfortunately, the answer does not appear to be that simple. Clinical signs of inflammation are unable to reliably distinguish between non-destructive forms of periodontal disease (gingivitis) and destructive forms (periodontitis). Physical assessments of damage to periodontal tissues, such as radiographic detection of bone loss or clinical attachment loss determined with a periodontal probe, measure damage from past episodes of destructive disease. New directions are needed to help to better diagnose periodontal diseases and some of the future possibilities are described and discussed.