1. Carmen D. Cohn Pulpal and periapical immune responses to infection

2. Carmen D. Cohn There is no evidence that necrotic pulp tissue per se can elicit periapical inflammation, in the absence of bacteria.

3. Carmen D. Cohn 78 monkey teeth with aseptically necrotized pulps 78 monkey teeth with aseptically necrotized pulps 26 bacteria-free 52 bacteria infected 7 months Apical periodontitis No apical inflammation Moller & Fabricius 1981

4. Carmen D. Cohn  Periapical responses to pulpal infection

5. Carmen D. Cohn Bacterial products IL-1 IL-2 MF Th B Periapical inflammation and bone destruction IL-2 + MHC-II IL-1, IL-6 TNFα PGE Ag

6. Carmen D. Cohn productsproducts MicrobialMicrobial Periradicular lesions - barrier Complement Granulomatous tissue Granulomatous tissue Defence elements Defence elements PMNs Epithelial plugs Antibodies MicroorganismsMicroorganisms Very few endodontopathogens can advance through the barrier.

7. Carmen D. Cohn Abscessed AP Actinomyces spp, Propionibacterium propionicum Infected radicular cysts Infected material displaced into the periapical tissues Extraradicular microorganisms Possible factor in the failure of the endodontic therapy.