The nature and significance of infection in periodontal disease

According to the hypothesis outlined, infection is an essential factor in periodontal disease which contributes largely to its clinical character; but infection is never more than one factor among several, and the others are accorded primary or determining importance. The infection is postulated as endogenous, as an overgrowth of certain resident parasites which, although harmless when in contact with healthy tissues, are enabled to proliferate, and in greater or less degree to invade the tissues, when these tissues are damaged by other causes. It seems probable that the inflammation, suppuration or ulceration of periodontal disease is contributed directly by infection. If the nature of this infection can be more precisely delineated and if, on the basis of such knowledge, the host factors that govern its course, including its tendency to be localized or invasive, can be defined, a long step will have been taken toward clarification of the etiology and pathogenesis of periodontal disease.