controversy below). local treatment an operculum (green arrow) over a partially erupted lower left third molar with inflammation and pus (right of green arrow under tissue) main article: pericoronitis pericoronitis is an infection of the operculum of a partially impacted wisdom tooth. it can be treated with local cleaning, an antiseptic rinse of the area and antibiotics if severe. definitive treatment can be excision of the operculum, however, recurrence of these infections is high. pericoronitis, while a small area of tissue, should be viewed with caution, because it lies near the anatomic planes of the neck and can progress to life-threatening neck infections.: 440–441 wisdom teeth removal wisdom teeth removal (extraction) is the most common treatment for impacted wisdom teeth. in the us, 10 million wisdom teeth are removed annually. the procedure can be either simple or surgical, depending on the depth of the impaction and angle of the tooth. surgical removal is to create an incision in the mucosa of the mouth, remove bone of the mandible or maxilla adjacent the tooth, extract it or possibly section the tooth and extract it in pieces. this can be completed under local anaesthetic, sedation or general anaesthetic. as of 2020, the evidence is insufficient to recommend one type of surgical practice over another.radiograph of symptomatic and infected impacted wisdom tooth near inferior alveolar nervenerve (green arrow) pierces the root of impacted wisdom tooth. tooth sectioned from around nervesocket of wisdom tooth with skeletonized inferior alveolar nerve (green arrow) intact recovery, risks and complications most people will experience pain and swelling (worst on the first post-operative day) then return to work after 2 to 3 days with the rate of discomfort decreased to about 25% by post-operative day 7 unless affected by dry socket: a disorder of wound healing that prolongs post-operative pain. it can be 4 to 6 weeks before patients are fully recovered with a full range of jaw movements. a cochrane investigation found that the use of antibiotics either just before or just after surgery reduced the risk of infection, pain and dry socket after wisdom teeth are removed by oral surgeons, but that using antibiotics also causes more side effects for these patients. nineteen patients needed to receive antibiotics to prevent one infection. the conclusion of the review was that antibiotics given to healthy people to prevent infections may cause more harm than benefit to both the individual patients and the population as a whole. another cochrane investigation has found post-operative pain is effectively managed with either ibuprofen, or ibuprofen in combination with acetaminophen. long-term complications can include periodontal complications such as bone loss on the second molar following wisdom teeth removal. bone loss as a complication after wisdom teeth removal is uncommon in the young but present in 43% of those of 25 years of age or older. injury to the inferior alveolar nerve resulting in numbness or partial numbness of the lower lip and chin has reported rates that vary widely from 0.04% to 5%. the largest study is from a survey of 535 oral and maxillofacial surgeons in california, where a rate of 1:2,500 was reported. the large variation in report rates is attributed to variations in technique, the patient pool and surgeon experience. other complications that are uncommon have been reported including persistent sinus communication, damage to adjacent teeth, lingual nerve injury, displaced teeth, osteomyelitis and jaw fracture. alveolar osteitis, post-operative infection, excessive bleeding may also be expected. treatment controversy many impacted wisdom teeth are extracted prior to the age of 25, when full eruption can be reasonably expected and before symptoms or disease have begun. this has led to a treatment controversy generally referred to as the extraction of asymptomatic, disease-free wisdom teeth. in 2000, the national institute of clinical excellence (nice) of the united kingdom set guidelines to discontinue the removal of asymptomatic disease-free third molars in the uk national health service, stating that there was no reliable research evidence to support a health benefit to patients from the prophylactic removal of pathology-free impacted third molar teeth, in addition to the risks of removal and cost to the service. advocates of the policy point out that the impacted wisdom teeth can be monitored and avoidance of surgery also means avoidance of the recovery, risks, complications and costs associated with it. following implementation of the nice guidelines the uk saw a decrease in the number of impacted third molar operations between 2000 and 2006 and a rise in the average age at extraction from 25 to 31 years. the american public health association (apha) has adopted a similar policy. those who argue against a blanket moratorium on the extraction of asymptomatic, disease-free wisdom teeth point out that wisdom teeth commonly develop periodontal disease or cavities which may eventually damage the second molars and that there are costs associated with monitoring wisdom teeth. they also point to the fact that there is an increase in the rate of post-operative periodontal disease on the second molar, difficulty of surgery and post-operative recovery time with age. the uk has also seen an increase in the rate of dental caries on the lower second molars increasing from 4–5% prior to the nice guideline to 19% after its adoption. although most studies arrive at the conclusion of negative long-term outcomes e.g. increased pocketing and attachment loss after surgery, it is clear that early removal (before 25 years old), good post-operative hygiene and plaque control, and lack of pre-existing periodontal pathology before surgery are the most crucial factors that minimise the probability of adverse post-surgical outcomes. asymptomatic disease-free impacted wisdom teeth in 21-year-old the cochrane review of surgical removal versus retention of asymptomatic disease-free impacted wisdom teeth suggests that the presence of asymptomatic impacted wisdom teeth may be associated with increased risk of periodontal disease affecting adjacent 2nd molar (measured by distal probing depth > 4 mm on that tooth) in the long term. few studies, however, met the criteria to be included in the cochrane review and those that were included provided very low quality evidence and had a high risk of bias. another study which was at high risk of bias, found no evidence to suggest that removal of asymptomatic disease-free impacted wisdom teeth has an effect on crowding in the dental arch. there is also insufficient evidence to highlight a difference in risk of decay with or without impacted wisdom teeth. one trial in adolescents who had orthodontic treatment comparing the removal of impacted lower wisdom teeth with retention was identified. it only examined the effect on late lower incisor crowding and was rated 'highly biased' by the authors. the authors concluded that there is not enough evidence to support either the routine removal or retention of asymptomatic impacted wisdom teeth. another randomised controlled trial done in the uk has suggested that it is not reasonable to remove asymptomatic disease-free impacted wisdom tooth merely to prevent incisor crowding as there is not strong enough evidence to show this association. due to the lack of sufficient evidence to determine whether such teeth should be removed or not, the patient's preference and values should be taken into account with clinical expertise exercised and careful consideration of risks and benefits to determine treatment. if it is decided to retain asymptomatic disease-free impacted wisdom teeth, clinical assessment at regular intervals is advisable to prevent undesirable outcomes (pericoronitis, root resorption, cyst formation, tumour formation, inflammation/infection). coronectomy main article: coronectomy coronectomy of impacted wisdom tooth post-op xray showing root remnants (red arrow) and inferior alveolar nerve (green arrow) coronectomy is a procedure where the crown of the impacted wisdom tooth is removed, but the roots are intentionally left in place. it is indicated when there is no disease of the dental pulp or infection around the crown of the tooth, and there is a high risk of inferior alveolar nerve injury. coronectomy, while lessening the immediate risk to the inferior alveolar nerve function has its own complication rates and can result in repeated surgeries. between 2.3% and 38.3% of roots loosen during the procedure and need to be removed and up to 4.9% of cases require reoperation due to persistent pain, root exposure or persistent infection. the roots have also been reported to migrate in 13.2% to 85.9% of cases. prognosis the prognosis for impacted wisdom teeth depends on the depth of the impaction. when they lack a communication to the mouth, the main risk is the chance of a cyst or neoplasm forming in the tissues around the tooth (such as the dental follicle), which is relatively uncommon. once communicating with the mouth, the onset of disease or symptoms cannot be predicted but the chance of it does increase with age. less than 2% of wisdom teeth are free of either periodontal disease or caries by age 65. further, several studies have found that between 30% – 60% of people with previously asymptomatic impacted wisdom teeth will have them extracted due to symptoms or disease, 4–12 years after initial examination. extraction of the wisdom teeth removes the disease on the wisdom tooth itself and also appears to improve the periodontal status of the second molar, although this benefit diminishes beyond the age of 25. epidemiology few studies have looked at the percentage of the time wisdom teeth are present or the rate of wisdom teeth eruption. the lack of up to five teeth (excluding third molars, i.e. wisdom teeth) is termed hypodontia. missing third molars occur in 9-30% of studied populations. one large scale study on a group of young adults in new zealand showed 95.6% had at least 1 wisdom tooth with an eruption rate of 15% in the maxilla and 20% in the mandible. another study on 5000 army recruits found 10,767 impacted wisdom teeth.: 246 the frequency of impacted lower third molars was found to be 72% in a swedish study, and the frequency of retained impacted wisdom teeth that are free of disease and symptoms is estimated to be between 11.6% to 29%, a percentage which drops with age. the incidence of wisdom tooth removal was estimated to be 4 per 1000 person years in england and wales prior to the 2000 nice guidelines. history farmer at the dentist, johann liss, c. 1616–17. wisdom teeth have been described in the ancient texts of plato and hippocrates. "teeth of wisdom" being from the latin, dentes sapientiæ, which in turn is derived from the hippocratic term, sophronisteres, from the greek sophron, meaning prudent. charles darwin believed the wisdom teeth to be in decline with evolution, a theory which his contemporary, paolo mantegazza, later proved to be false when he discovered darwin was not opening the jawbones of specimens to find the impacted tooth stuck in the jaw. in the late 19th and early 20th centuries, the collision of sterile technique, anaesthesia and radiology made routine surgery on the wisdom teeth possible. john tomes's 1873 text a system of dental surgery describes techniques for removal of "third molars, or dentes sapientiæ" including descriptions of inferior alveolar nerve injury, jaw fracture and pupil dilation after opium is placed in the socket. other texts from about this time speculate on their de-evolution, that they are prone to decay and discussion on whether or not they lead to crowding of the other teeth.