Whether or not a tooth extraction is required for straight teeth depends on the specific circumstances of each patient, that is, the amount of teeth as well as the amount of bone in each patient, to determine whether or not a tooth extraction is required. However, in the current clinical work, since the majority of patients are in a situation where the amount of teeth is greater than the amount of bone, the majority of patients need extractions for cosmetic dentistry. This is mainly due to our gradual evolutionary development, our teeth are actually the more developed teeth according to tradition, each person will have 28-32 teeth. Although there is now a percentage of people with wisdom teeth that have degenerated and are congenitally missing. But the majority of people have wisdom teeth, and this relatively large number of teeth, to be arranged on the jaw arch, will naturally lead to the protrusion of the jaw, which means that our jaws should be congenitally protruding, just like orangutans and monkeys, whose jaws are significantly inflated because they have to chew roots and leaves. We humans do not require such an expanded jaw nowadays, but we still have a larger amount of teeth. From this perspective, most people need to have their teeth extracted for a full set of teeth. Very few people with enough jawbone for teeth to erupt can be considered for cosmetic dentistry without extractions.