Procedures to remove the pulp without toxic chemicals were introduced in the early part of the 19th century and small, hooked instruments were used. The advent of local anesthesia at the beginning of the 20th century made pulpectomy a painless procedure.
Signs of root canal infection, such as abscesses with fistulae, were also dealt with historically using highly toxic chemicals. These substances were introduced to the root canal, and forced through the foramen into the fistula. Often the treatment was more damaging than the disease condition itself, and the tooth and parts of the surrounding bone were often lost in the process. While relief of pain is still a primary goal of endodontic treatment, patients also may want to exclude the compromised tooth, as both a general and local health hazard. This means that intra- as well as extraradicular infections should be eradicated and that materials implanted in the root canal should be innocuous and not cause adverse tissue reactions or systemic complications. Using modern endodontic treatment procedures, these treatment objectives can be attained in the large majority of cases.
*Textbook of Endodontology. p. 3