In the situation that a tooth is considered so threatened (because of decay, cracking, etc.) that future infection is considered likely or inevitable, a pulpectomy, removal of the pulp tissue, is advisable to prevent such infection. Usually, some inflammation and/or infection is already present within or below the tooth. To cure the infection and save the tooth, the dentist drills into the pulp chamber and removes the infected pulp and then drills the nerve out of the root canal(s) with long needle-shaped hand instrument known as files (H files and K files) instead. Starting with 15 number H which is also called as pathfinder and after that files number increased up to 35 in molars and up to 50/55 number file in anterior tooth to broad the canals for a successful treatment.After this is done, the dentist fills each of the root canals and the chamber with an inert material and seals up the opening. This procedure is known as root canal therapy. With the removal of nerves and blood supply from the tooth, it is best that the tooth be fitted with a crown.
The standard filling material is gutta-percha, a natural polymer prepared from latex from the percha (Palaquium gutta) tree. The standard endodontic technique involves inserting a gutta-percha cone (a "point") into the cleaned-out root canal along with cement and a sealer. Another technique uses melted or heat-softened gutta-percha which is then injected or pressed into the root canal passage(s). However, as gutta-percha shrinks as it cools, thermal techniques can be unreliable and sometimes a combination of techniques is used. Gutta-percha is radiopaque, allowing verification afterwards that the root canal passages have been completely filled in, without voids.
An alternative filling material was invented in the early 1950s by Angelo Sargenti. It has undergone several formulations over the years (N2, N2 Universal, RC-2B, RC-2B White), but all contain paraformaldehyde. The paraformaldehyde, when placed into the root canal, forms formaldehyde, which penetrates and sterilizes the passage. The formaldehyde is then theoretically transformed to harmless water and carbon dioxide. The outcome is better than a root canal done with gutta percha according to some investigations. There is however a lack of indisputable, scientifically made studies according to the Swedish Council on Health Technology Assessment.