Under the hard enamel and the dentine, hidden in the interior of the tooth, there is a vacuum filled with soft tissue which reaches to the tips of the root. This pulp, commonly referred to as "nerve", consists of connective tissue with blood- and lymph tissue as well as nerve fibers. Through bacteria, resulting from cavities, as well as through mechanical or thermal irritation, this pulp can get infected. The resulting pulpitis can be temporary or irreversible. In its acute stages, it is accompanied by strong pain. In this case, a root canal is necessary. The infected tissue and the corresponding bacteria are removed as completely as possible and a space for a filling is formed. The bacteria-proof filling of the canal system completes the treatment.