Root canal therapy may be necessary in the last effort to salvage the infected tooth from caries, fractures, and trauma. Even though there are similarities in the root canal system in each type of tooth (i.e. incisors, bicuspids, molars), no two teeth have the exact same root canal system.
For simplification, most incisors have single root system, whereas most molars have multiple root system. Root canal therapy involves complete removal of infected tissue form each root canal system followed by stabilization with an inert base material, which is usually seen as white or radio-opaque on radiograph. The following before and after radiographs show the complexity of each root canal system.
Asymptomatic necrotic incisor with periapical pathology. Root canal therapy was rendered. Notice the presence of lateral or accessory canal (side branch) leading from the main branch in the apical third or near the end of the root canal system.
Symptomatic acute periradicular periodontitis of the bicuspid that is supporting a 3-unit bridge. Root canal therapy was performed to remove the infection. Also notice the presence of lateral canal leading from the main branch.