In one of the series of talks on root canal treatment, I have briefly described to you the structure of the tooth and how root canal treatment is performed. So, which dental diseases require root canal treatment and which do not? In other words, what problems can be solved by root canal therapy and what dental problems cannot be solved by root canal therapy? In fact, it is very difficult for us, the general public, to accurately correspond diseases to treatments like this one, because it requires considerable expertise. Therefore, I will introduce to you below several common dental diseases that are suitable to be treated by root canal therapy, and some relatively uncommon cases that I will discuss separately in the form of a topic in a future article. As the name implies, pulpitis is the inflammation of the tooth pulp, the so-called pulp refers to those blood vessels and nerve tissue inside the tooth, and when these tissues are inflamed, the pain is generally more obvious. Sometimes it can make people restless and difficult to eat and drink, which is what the saying “a toothache is not a disease, but a pain that really kills you” refers to. It causes pain when the tooth is cold or hot, sometimes biting pain, and even severe pain at night. Sometimes, the pain radiates to the head and face and can be mistaken for a headache. Most cases of pulpitis do not resolve on their own and, if not treated promptly, can lead to other more serious consequences such as periapical inflammation and eventual extraction of the tooth. Therefore, once pulpitis has developed, thorough root canal treatment is required to remove the infected pulp and seal the root canal with artificial material to eliminate the path of reinfection in order to relieve the pain and save the affected tooth. The vast majority of periapical infections develop from pulpitis. When pulpitis (i.e., inflammation inside the tooth) is not treated in a timely manner, it progresses to the root of the tooth, causing inflammation of the tissues surrounding the root, which is called periapical inflammation. We can think of periapical inflammation as a result of inflammation inside the tooth spreading to the outside of the tooth. With periapical periodontitis, the tooth will have biting pain, sometimes severe and sometimes relatively mild, and the acute attack of inflammation will cause some degree of tooth loosening and sometimes swelling of the tooth bed or overflow of pus. However, some patients with periapical periodontitis do not experience much discomfort because they are more resistant and the inflammation is in a chronic progressive process. However, either type of periapical infection will not heal on its own without treatment. Moreover, treating periapical inflammation is more difficult than treating pulpitis, and only timely and thorough root canal treatment is possible to eliminate the inflammation and preserve the affected tooth. Third, traumatized teeth and cryptically cracked teeth There are times when a tooth is accidentally damaged, resulting in a fractured tooth, but the root is still in good condition, in which case the root can be saved by root canal treatment and then restored. The so-called hidden cracked tooth refers to the existence of some cracks on the tooth surface or inside the tooth, some of these cracks are easy to find, some need to be found after careful examination, if the crack is deep, it will cause the tooth to have symptoms similar to pulpitis or periapical inflammation, which requires the use of root canal treatment, and the crown should also be restored. Fourth, restoration needs Some teeth are not inflamed, but it is misplaced or misshapen in size, and in some restoration designs it is necessary to root canal them and then make crowns to achieve cosmetic results. After some teeth are missing, it is necessary to root canal the teeth on both sides of the missing tooth and then design the crown (crown bridge) as a whole to restore the function of the missing tooth.