Wisdom teeth are the teeth closest to the throat, and there are four of them, two in the upper and lower jaws, if they all grow out. There are 32 teeth in the human permanent dentition, of which the last four molars are located at the very back of the upper and lower dental arches, and are also known as wisdom teeth because they erupt around the age of 18. Compared to the baby teeth that emerge in early childhood and the permanent teeth that are replaced in childhood, the wisdom teeth usually emerge when the human mind is already mature. The growth of wisdom teeth varies greatly from one person to another, with some people growing before the age of 20, others growing at 40 or 50, and some not growing for life. Some people may have only one or two wisdom teeth, and some wisdom teeth may even stop growing halfway, which is called wisdom tooth blocking. Wisdom teeth are located from the middle of the incisors, and if there is an eighth tooth, it is a wisdom tooth. Due to the gradual refinement of food in human evolution, the chewing organ has degenerated and the jawbone no longer needs strong chewing power, so there is a tendency for it to gradually become smaller. In late adolescence, the jawbone develops to nearly adult size. In some cases, the jawbone is not large enough for the wisdom teeth to erupt. The wisdom tooth then becomes blocked in the jawbone and grows in the other direction. Only part of the crown of the tooth may be exposed to the gums, or it may be completely buried in the jawbone. The roots of the tooth may become deformed or grow dangerously towards the maxillary sinus or the area where the mandibular nerve is located. Due to the lack of space, the blocked wisdom tooth grows in various directions, usually at an angle to the neighboring teeth. They can grow toward the adjacent teeth (proximodistal angular obstruction), away from the adjacent teeth (distodistal angular obstruction), or horizontally or vertically. Wisdom teeth that must be removed Wisdom teeth not only have no chewing function, but also have a series of hazards or potential hazards, so early removal is the best policy. Due to incomplete eruption, the gingiva on its posterior side covers part of the crown to form a pericoronal pocket, which accumulates food and bacteria, causing frequent inflammation of local soft tissues and pain, and even leading to difficulty in eating due to restricted opening. The general anti-inflammatory treatment treats the symptoms but not the root cause, some people are reluctant to remove the inflammation, no more pain, and can eat, resulting in inflammation again and the symptoms become more serious. Most of the wisdom teeth are tilted forward and obstructed, that is, they are tilted at an angle of about 45 degrees on the second molar, and the two crowns form an angle and embed food, and after a long time, the second molar forms caries until pulpitis and severe pain. Another consequence is that the anteriorly inclined wisdom teeth keep exerting force on the second molar, causing periodontitis and painful loosening, and the second molar has to be extracted, or the two teeth have to be extracted, and the chewing function is seriously damaged. Although the eruption direction of some wisdom teeth is more or less normal, the contact point with the second molar is not normal, so as to embed food, and it is not easy to brush the gap between teeth when brushing, and it is very easy to cause the second molar caries and shorten its service life. Nowadays, many people think that as long as the tooth does not hurt, there is no need to treat or extract it, but this view is incorrect. Because if it hurts, it shows that it has caused irreversible damage to the normal teeth and even the organism, and it is difficult to pull out the wisdom teeth at this time to recover the loss caused by wisdom teeth. Third, the wisdom teeth often can not form a good bite relationship with the opposing teeth, for a long time can lead to the temporomandibular joint popping, mouth pain, night grinding and other symptoms, the physical and mental health of young adults is more affected. There are also some obstructed wisdom teeth that are the foci of some trigeminal neuralgia. Wisdom teeth generally erupt around the age of 16. Since the roots of these teeth are not fully formed when they first erupt, they are easy to remove, and their removal at this time avoids damage to the second molars and the body, so early removal is the best treatment option. Wisdom teeth that can be retained Not all wisdom teeth must be extracted. If the wisdom teeth are in a positive position, there is no history of inflammation and pain in the soft tissue around the crown of the wisdom teeth, the wisdom teeth are not decayed, and the blind pocket can be eliminated by gingival flap removal, the wisdom teeth can be considered to be retained, but oral hygiene must be paid attention to in general.