[Pathogenesis of apical periodontitis and its effects on the body].
During the last 25 years there have been major advances in understanding the etiology, pathogenesis and maintenance of inflammatory processes taking place in the periapical space. Polymicrobial infection of the pulp chamber is of primary importance in initiating periapical inflammation. Egress of bacteria and their antigenes stimulate the immune system to form a granulation tissue around the apical area. Local immune response eliminates excess number of invading organisms. However, in parallel with protective reactions, local activity of immunocompetent cells and their soluble products also contribute to tissue damage, bone resorption and perpetuation of inflammation. Present data indicate that interaction of T-lymphocytes and macrophages is crucial in this process.