A century of progress in understanding periodontal disease.

Throughout the 20th century, investigators and clinicians sought to discover the causes and trace the natural history of periodontal disease. Noteworthy progress has been made on several fronts. It was once believed that oral hygiene and age accounted predominantly for variances in the prevalence and severity of periodontal disease; now, a number of innate, acquired, and environmental risk factors have been identified. Light has been shed on the roles in periodontal disease pathogenesis of both specific bacteria and bacterial complexes and host immunoinflammatory responses. Insight into periodontal wound healing has fostered promising approaches to promoting regeneration of damaged periodontal structures. Finally, although theories of "focal infection" as a primary cause of systemic disease have been discredited, recent studies have confirmed the existence of an intimate connection between oral and systemic health. The progress made in understanding the nature of periodontal disease has been complemented by equally noteworthy therapeutic advances. The coupling of surgical and medical approaches to treatment ushers in a new era in the management of periodontal disease.