Risk assessment of the toxicity of solvents of gutta-percha used in endodontic retreatment.

Three randomly assigned groups of single-canaled extracted teeth obturated with gutta-percha were retreated using controlled application of one of three organic solvents: chloroform, xylene, or halothane. Two additional groups of teeth served as positive and negative controls. Residual volume of solvent expressed through the apical foramen during retreatment was determined by the difference of pretreatment and posttreatment weights of hermetically sealed receptacles attached to the root surface of the teeth. Results indicate that the amount of solvent that has been determined to have leached out through the apical foramen is several orders of magnitude below the permissible toxic dose. Thus, it is proposed that the use of any of the aforementioned solvents used in the retreatment of root canals would pose negligible risk to the patient.