Understanding the pathogenesis of periodontitis: a century of discovery.

The twentieth century was an especially notable time for research advances into the understanding of the aetiology and the pathogenesis of periodontitis. Beginning in 1900, using dark-field preparations, investigators began to implicate certain microorganisms, such as amoebae, as causing periodontitis. Today, using modern molecular techniques, we believe we have identified the primary causative agents of adult periodontitis. In 1900, histological sections of periodontal tissues at autopsy provided clues as to how periodontal pockets probably formed. Today there is a wealth of cellular and molecular data that suggest the actual pathways that the susceptible host uses to initiate periodontal tissue destruction. We now also appreciate that periodontitis may be a significant risk factor for systemic disease. A very exceptional 'century of discovery' into the nature of periodontal diseases should now lead to a new era of better diagnosis, prevention and treatment for this ubiquitous disease.