Fate of the tissue in lateral canals and apical ramifications in response to pathologic conditions and treatment procedures.

INTRODUCTION This article reviews and reports on the histopathologic and histobacteriologic status of the tissue in lateral canals and apical ramifications (LC/AR) in diverse clinical conditions as well as in response to endodontic treatment. METHODS In total, serial sections from 493 human tooth specimens obtained by extraction or apical surgery were screened for the presence of LC/AR. RESULTS LC/AR were observed in about 75% of the teeth. In clinically vital teeth, vital tissue was consistently found in LC/AR. In teeth with periodontal disease, the whole pulp became necrotic only when the subgingival biofilm reached the main apical foramen. In teeth with pulp exposure by caries, the tissue in LC/AR remained vital as far as the pulp tissue in the main canal did so. When pulp necrosis reached the level of the LC/AR, the tissue therein was either partially or completely necrotic. Chemomechanical preparation partially removed necrotic tissue from the entrance of LC/AR, whereas the adjacent tissue remained inflamed, sometimes infected, and associated with periradicular disease. Vital tissue in LC/AR was not removed by preparation. In cases in which lateral canals appeared radiographically "filled," they were actually not obturated, and the remaining tissue in the ramification was inflamed and enmeshed with the filling material. CONCLUSIONS Overall, the belief that lateral canals must be injected with filling material to enhance treatment outcome was not supported by literature review or by our histopathologic observations. It appears that strategies other than finding a technique that better squeezes sealer or gutta-percha within LC/AR should be pursued to effectively disinfect these regions.