A dental extraction (also referred to as exodontia) is the removal of a tooth from the mouth. Extractions are performed for a wide variety of reasons, including tooth decay that has destroyed enough tooth structure to render the tooth non-restorable. Extractions of impacted or problematic wisdom teeth are routinely performed, as are extractions of some permanent teeth to make space for orthodontic treatment.Extractions are often categorized as "simple" or "surgical". Simple extractions are performed on teeth that are visible in the mouth, usually under local anaesthetic, and require only the use of instruments to elevate and/or grasp the visible portion of the tooth. Typically the tooth is lifted using an elevator, and using dental forceps, rocked back and forth until the periodontal ligament has been sufficiently broken and the supporting alveolar bone has been adequately widened to make the tooth loose enough to remove. Typically, when teeth are removed with forceps, slow, steady pressure is applied with controlled force. Surgical extractions involve the removal of teeth that cannot be easily accessed, either because they have broken under the gum line or because they have not erupted fully. Surgical extractions almost always require an incision. In a surgical extraction the doctor may elevate the soft tissues covering the tooth and bone and may also remove some of the overlying and/or surrounding jawbone tissue with a drill or osteotome. Frequently, the tooth may be split into multiple pieces to facilitate its removal. Surgical extractions are usually performed under a general anaesthetic.