Theoretically, toothache caused by tooth decay is in most cases an inflammation of the tooth pulp, that is, toothache caused by pulpitis. At this time, if the tooth is extracted and there is no more, the pain of the pulpitis lesion will be naturally relieved, but in actual clinical work, this is absolutely wrong because it is not appropriate in the way of treatment. The decayed tooth can be completely preserved and there is no need for extraction. It is just like when we have a broken arm, the best way to fix it is with a plaster cast or an incised titanium plate, not a direct amputation. This analogy is slightly exaggerated, but the same is actually true for teeth. For decayed teeth that have progressed to the stage of pain. We can treat the tooth thoroughly by opening the pulp and drainage and root canal treatment so that it is no longer painful, and finally protect the tooth by applying a crown restoration. The tooth will still be able to serve the chewing function of the mouth for a long time instead of having to be extracted because of the decay.