Wisdom tooth is the last tooth to erupt, because it usually erupts between 18-30 years old, compared to other teeth, people at this age are already mentally mature, so it is called “wisdom tooth”, or the third molar. Wisdom teeth are usually 4 upper, lower, left and right, and the third maxillary molar is missing in clinical practice, and some people do not have wisdom teeth, so the number of human permanent teeth is 32-28. Due to the evolution of human beings, the food becomes more and more refined and the chewing function of human beings declines, and the corresponding jaw bone is gradually shrinking. Compared to bone, the evolution of teeth was much slower. This has resulted in a disproportion between the amount of teeth and bone in modern humans, mainly because the amount of teeth is greater than the amount of bone, which means that by the time the wisdom tooth erupts, there is not enough space in the jawbone, especially the mandible, to accommodate it. This results in crowded teeth, incomplete eruption of wisdom teeth, and even if they do erupt, they are still backwards. The most common disease caused by incomplete eruption of wisdom teeth is pericoronitis. The uneven wisdom teeth and the adjacent teeth are directly prone to food stuffing, plus the wisdom teeth are located at the very back of the tooth row, which is very difficult to self-clean and brush. The accumulation of food over a long period of time causes bacteria to multiply and eventually pericoronitis occurs. The third molar eruption process or eruption difficulties, part of the crown is covered by the free gingival part, between the crown and the gingival flap to form a blind pocket (gingival pocket), the blind pocket often have food debris and bacterial retention. This local condition makes it easy for bacteria to grow and multiply. Wisdom tooth pericoronitis can be triggered by cold, fatigue or other causes of decreased body resistance, or by local trauma (e.g., bite wounds to the jaw teeth) and other factors. The disease is most often seen in the third mandibular molar because it often lacks sufficient position for eruption and is easily blocked. The typical symptoms of pericoronitis are pain, swelling, thickening, and bad breath. These diseases often make people suffer a lot and have trouble sleeping and eating. If you have a painful wisdom tooth, you should go to the hospital to get treatment, do not delay, otherwise there will be various interstitial infections around the wisdom tooth to cause more serious diseases. The treatment of pericoronitis is usually a local cleaning, cleaning all the food residue and thick liquid around the crown, and then taking some oral anti-inflammatory and pain-relieving drugs. After the acute pain has disappeared, if the doctor thinks that the tooth is no longer necessary, he or she will recommend that it be extracted. After extraction, there is no need to set the tooth, and it will not affect the chewing function, which is a once and for all method.