Dental extractions are required when either the teeth have reached a certain level of decay through neglect or are required to allow other teeth to come through into their normal position in the mouth.
The most common reasons for tooth extraction are decay and periodontal disease and the teeth are just not worth saving.
Some patients may require extractions for aesthetic reasons as they are unhappy with the look of their teeth. Typically, when preparing for dentures, the surgical tooth extractions (or clearances) are performed under general anaesthetic.