The authors describe the various etiological types of periodontopathies and discuss those due to inflammatory conditions in greater detail. The original studies that enabled the role of the bacterial plaque to be demonstrated are reviewed, and new data presented which attributes a specific pathogenic action to certain bacterial strains in this particular form of the disease, without suggesting that they are the only etiological factor involved. The importance of occlusal injury in periodontal disease is then evaluated, results of clinical studies tending to confirm the role of traumatic factors in the progression of alveolysis. The occlusal factor should therefore be integrated into the stomatognathic system. The results of systematic dentofacial orthopedic examinations in patients with periodontopathies are reported, and other pathogenic factors contributing to disequilibrium of the dental organ outlined. Several clinical cases are presented. The results of these observations are employed to redefine the notion of function equilibrium which must be taken into account when treating the disease prophylactically, and to recognize those cases in which it is disturbed. Neuromuscular reeducation is then necessary to avoid recurrence of the periodontal disease.