An extraction is the removal of a tooth. It is used when the teeth are crowded and there is not enough room for all of them. The space created by removal of the tooth provides room for the others to rotate and line up straight. All of the extraction space is completely closed; there are no gaps at the end of treatment.
Deciding which tooth to remove is very important. You usually extract the side tooth closest to the crowding, but other factors may interfere with this decision. If in taking out a side tooth, you leave in a tooth with a short root, you will have compromised the case, as short roots have a greater long-term risk of failure than normal roots. Other features that may put a tooth at risk are fillings, crowns, root canals, and bone loss. Having to take out a different tooth will make the case more difficult and cause the treatment time to be extended. It is of paramount importance that you keep the most important teeth.