Root canal therapy is a treatment that I really enjoy. I enjoy the more challenging work, and one of the most challenging treatments in dentistry is root canal therapy. The root canal system of a tooth is very complex, like a large tree with a trunk and branches, and it is challenging to get such a complex root canal system in place. It requires more skill to master and involves the most instruments, and treating a single tooth often requires setting out 3 large tables of tools. After you have spent a long time putting a tooth’s root canal in place, looking at the post-operative x-rays feels like you are admiring a work of art, very beautiful and very rewarding. The inside of our teeth are hollow and hold the pulp inside, just like bone has marrow in it. If the pulp is infected by bacteria because of tooth decay or periodontal disease, etc., the symptoms of toothache will appear. Some of this pain can be very intense, with a half-sided headache. In more serious cases when the inflammation is not treated in time deep below the root of the tooth, one side of the face may swell up. To eliminate the inflammation, oral medication cannot completely solve the problem, because the medication, through the blood circulation, has already reached the inside of the tooth minimally, and in some cases the capillaries inside the tooth itself have been destroyed, and the medication cannot reach here. We can only take out the infected pulp, disinfect the root canal and fill it up tightly. This is what we often call root canal treatment or “nerve killing” To do root canal treatment, we must first find the root canals, which are very small in humans, and the number of root canals varies from tooth to tooth. To find them all, it requires the doctor’s knowledge and experience, and here comes the advantage of the dental microscope, which makes it easier to find them by magnifying a tooth 10 times. Once the root canals are found, we need to remove the infected pulp tissue from the inside of the root canals and also remove the infected inner walls of the root canals. It is like a room that has not been cleaned for a long time, to make it look new not only the floor has to be cleaned, but also the ceiling and walls have to be cleaned. This is the time to use special instruments (currently the most advanced equipment is the specially designed rotating nickel-titanium instruments) that can clean all parts of the root canal without destroying the structure of the root canal, we certainly do not want to clean the room, clean the debris and end up with a collapsed house. To clean out the root canal infection, there are some residual debris stuck on the root canal wall in addition to the swarf brought out by the rotating nickel-titanium instruments. Well, now that the root canal is clean, the cavity is completely filled up to keep the bacteria out. At this time we use a material called dental cement, which is stable and can be used for a long time in the root canal. Nowadays, the most advanced dental cement filling system is the hot cement filling system, which heats the cement to a certain temperature and makes it fluid, and then fills the whole root canal system automatically by vertical pressure. Before the root canal treatment, we have anesthesia, so the whole process is painless. Only the tooth to be treated is exposed and the rest of the mouth is under the rubber barrier, which isolates the saliva, because saliva contains bacteria, and if saliva flows into the root canal while cleaning, it cannot be completely sterile. At the same time, it is very important to have the rubber barrier to prevent the treatment instruments from falling down into the throat. After the root canal treatment, the strength of the tooth is decreased because of the previous decay and the fact that we have to grind away some tooth tissue during the treatment in order to allow the instruments to enter the inside of the root canal smoothly. In order to prevent the tooth from fracturing due to the loss of strength, we have to make a full crown restoration for the tooth, and sometimes a pile is placed in the root canal for reinforcement before the crown is made. With the above series of measures, the tooth with toothache can be effectively treated, and with daily oral maintenance and regular review, our affected tooth can be preserved for a long time.