That is root-tip amputation. This kind of intervention is needed when the tooth can not be treated by the usual way. Such intervention is necessary when for example there is a chronic inflammation around the root-tip, or such pulp, which can not be treated with root-filling for some reasons, or if the root-tip of the tooth reaches into the cyst-cavity of the jawbone and the doctor decides to keep the tooth. After the intervention the treated area slightly swells up, it is useful to have a rest for a day or two. Some analgesic or cold compress may also be needed.