Figure 1. Common sites of bacterial invasion of dentin. Bacteria invading from the oral cavity (i, ii, iii, iv, v) extend toward the dental pulp space (A) and may result in inflammatory disease and infection of the pulp and periapical tissues. (B) Periapical radiograph demonstrating chronic periapical periodontitis of an upper left central incisor subsequent to infection of the root canal via an enamel-dentin crack. Bacteria invading radicular dentin (v) from an infected root canal invade outward toward the external root surface (C) and may be responsible for persistent root canal infection and inflammatory disease of the surrounding tissues. (Reprinted and modified with permission from Love, 1997.)
