In the daily practice of the Department of Dentistry, we often encounter patients who come to the clinic with toothache. Their teeth not only hurt when they are cold or hot, but sometimes they have severe pain at night and even have difficulty sleeping. After diagnosis, the doctor will usually say, “Your tooth needs to be nerve-killed”, or you may hear the doctor say, “Your tooth needs root canal treatment”. So, what exactly are “nerve killing” and “root canal therapy”? What is the difference between them? Why is this treatment needed to relieve tooth pain? To answer these questions, we need to start with the structure of the tooth. Our teeth can be described as “strong on the outside, soft on the inside”. The outer layer of the tooth is very hard and wear-resistant, but inside this “strong exterior” is a cavity with many blood vessels and nerves, which is the “soft interior” of the tooth. We call these soft tissues inside “pulp”. When the pulp becomes inflamed, it causes pain and is called “pulpitis”. In the past, the treatment for this type of pulpitis was to drill the tooth open and use drugs to “kill” the inflamed pulp inside the tooth to relieve the pain, which is commonly known as “nerve killing”. As you can see, the term “nerve killing” refers to some of the early treatments. With the comprehensive innovation of treatment concept and the great progress of treatment technology, this treatment method has been largely eliminated. The modern method of “root canal treatment” is commonly used. As we mentioned earlier, the interior of the tooth is actually a cavity, which we call the “root canal system”. In contrast to the simple “nerve killing”, the “root canal treatment” is not only to “kill” the pulp in the “root canal”, but also to “remove” the pulp from the tooth. “It is also necessary to remove the pulp from the “root canal”, then to clean and sterilize it thoroughly, and to fill the “root canal” tightly with artificial filling material. This is called “root canal treatment”. ”Root canal therapy is a complex procedure and may require multiple visits to complete the entire treatment. However, this method is able to eliminate the maximum amount of inflammation and prevent reinfection. The longevity of a tooth is largely determined by how well a “root canal” is done. Moreover, not only for pulpitis, but also for other diseases of the tooth (e.g., periapical periodontitis), root canal treatment is required to cure the tooth. However, it is not easy for the doctor to explain the process of root canal treatment to the patient in detail and it is difficult for the patient to fully understand it. Therefore, sometimes doctors use the more common term “nerve killing”, just to make it easier for patients to accept, but the actual treatment is still the “root canal” method. With the continuous popularization of oral health knowledge and the gradual improvement of the general public’s understanding of oral treatment, I believe the term “nerve killing” will one day fade out of our vision, and the standardized “root canal treatment” will be understood and accepted by more patients.