There are 32 teeth in human permanent dentition, and the last four third molars are located at the last side of the upper, lower, left and right dental arch. Because they erupt between the ages of sixteen and twenty-four, they are also called wisdom teeth, or simply wisdom teeth.

However, due to evolution and food refinement, human jaws tend to become smaller because they no longer need strong chewing power. If you want to accommodate the same number and size of teeth on this smaller jaw, there will often be a problem of insufficient space between teeth, so it will be crowded, long-inverted, long-curved, or unable to grow, which is called impaction. Statistically speaking, wisdom teeth do not grow out most often, so it is customary to call them impacted wisdom teeth.