Many orthodontic patients in the first orthodontic consultation when they hear that there is a possibility that the teeth may also need to be extracted, they feel very incomprehensible, and even refuse to orthodontic because they can not accept. We often hear in the consultation for this kind of situation is: “the old people said the teeth can not just remove, once removed, the teeth will be loosened after old age”; also often heard this kind of question: “the nerve of the tooth is connected to the head, pulling teeth will pull the nerve, affecting the There is no scientific basis for these questions, but there is a certain market for them among the general public. I hope that through this article, we can try to popularize the basic orthodontic knowledge to everyone. First of all, we need to have a basic knowledge, each of our teeth are growing in the bone, we usually see only the crown part of the teeth, and most of the teeth are buried in the bone, and each tooth has its own independent fossa, we call the alveolar fossa. The inside of the tooth is hollow and has small nerves and blood vessels running through it to provide nutrition and sensation to the tooth. If a tooth is extracted, the socket is filled with blood clots that slowly mechanize into bone, and the socket is slowly filled with new bone tissue. There is no such thing as affecting the nerves in the brain. So why does orthodontics require the removal of several intact teeth? We can use the analogy of sitting in a seat, that is, now we have 12 seats, but sat 14 people, so either many people sit only half of the buttocks, slanted body crooked, this phenomenon in the mouth is the formation of crowded teeth, overlapping teeth arrangement; or as in the round table to add two positions, to join all the stools are moved back a little to accommodate more chairs, this This situation occurs in the orthodontic inside is the formation of teeth protrusion, which is commonly known as “buck teeth”. Therefore, if we want to align the teeth without protruding, we have to remove some teeth that are not relatively functionally important to provide a place for the remaining teeth to “sit comfortably” in the mouth. Routinely, the front teeth play a key role in aesthetics, and the molars are large and take up most of the chewing function, so they are generally not considered for extraction. As to whether the fourth or fifth tooth should be extracted, it is up to the doctor to make a comprehensive consideration based on the examination results. However, some parents still feel that their child has only one crooked tooth, so why should two or four be extracted, thinking that it is too bad to sacrifice four good teeth for one. We understand that parents are cautious before making decisions for their children, but it is also due to the fact that they do not have a basic understanding of the alignment and structure of the teeth in the mouth. Our teeth are arranged symmetrically from left to right based on the midline of the face, and the midline is aligned with the point between the eyebrows, the tip of the nose, and the middle of the person. If the number or arrangement of teeth is not symmetrical from left to right, it will affect the position of the midline of the teeth or the arch of the teeth will not be symmetrical from left to right. There is definitely an impact on the aesthetics. Now that we know why teeth are extracted, parents are still worried because they often hear doctors say that teeth should not be extracted easily and that teeth that can be kept should be preserved as much as possible. This concept is correct, if the tooth is extracted and not restored, it is indeed easy to have the problem that the teeth in the opposite jaw will be elongated and wasted and the neighboring teeth will be tilted to the missing position because of the incomplete tooth alignment. However, orthodontic tooth extraction refers to the extraction of teeth under the treatment of orthodontist, and the gap between the extracted teeth should be completely closed before the end of orthodontic treatment by adjusting the position of teeth, that is, after the end of orthodontic treatment, the upper and lower teeth alignment is complete without gap, and the teeth alignment is neat, and the more important point is that the orthodontist should adjust the upper and lower teeth occlusion to a one-to-two relationship through the movement of teeth, and the normal upper and lower teeth The normal upper and lower teeth bite is a cusp-to-socket relationship, like two gears, one tooth is embedded between two teeth of the other gear, so as to achieve maximum power. Only by adjusting the bite relationship to such a functional bite through orthodontics can we ensure a healthy and long-lasting dental, joint and jaw surface in the future.