The vast majority of adults have between 28 and 32 permanent teeth, of which more than 28, the extra large teeth are wisdom teeth, in the innermost of the back teeth, also called the third molar, which is the eighth tooth counted from the middle of the incisors, usually begin to erupt after the development of intelligence at about twenty years of age, and some people grow out only at an older age, so it is also called intelligent teeth, or wisdom teeth for short. Many people’s wisdom teeth do not grow well, this is because in the process of human evolution, life habits have changed, the food obtained more and more soft, no longer need strong chewing force, gradually causing the jawbone degeneration, shortening, and the number of teeth size change little (basically not smaller), so that when the wisdom teeth grow out other teeth have filled the alveolar bone, there is no wisdom teeth position, so that the wisdom teeth eruption obstructed In this case, the wisdom teeth will be crowded, grow backwards, grow curved, or not grow out, etc. This is also known as an obstructed wisdom tooth.