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Impacted wisdom teeth (or impacted third molars) are wisdom teeth which do not fully erupt into the mouth because of blockage from other teeth. If the wisdom teeth do not have an open connection to the mouth, pain can develop with the onset of inflammation or infection or damage to the adjacent teeth. Wisdom teeth likely become impacted because of a mismatch between the size of the teeth and the size of the jaw. Impacted wisdom teeth are classified by their direction of impaction, their depth compared to the biting surface of adjacent teeth and the amount of the tooth's crown that extends through gum tissue or bone. Impacted wisdom teeth can also be classified by the presence or absence of symptoms and disease. Screening for the presence of wisdom teeth often begins in late adolescence when a partially developed tooth may become impacted. Screening commonly includes clinical examination as well as x-rays such as panoramic radiographs. Infection resulting from impacted wisdom teeth can be initially treated with antibiotics, local debridement or soft tissue surgery of the gum tissue overlying the tooth. Over time, most of these treatments tend to fail and patients develop recurrent symptoms. The most common treatment is wisdom tooth removal. The risks of wisdom tooth removal are roughly proportional to the difficulty of the extraction. Sometimes, when there is a high risk to the inferior alveolar nerve, only the crown of the tooth will be removed (intentionally leaving the roots) in a procedure called a coronectomy. The long-term risk of coronectomy is that chronic infection can persist from the tooth remnants. The prognosis for the second molar is good following the wisdom teeth removal with the likelihood of bone loss after surgery increased when the extractions are completed in people who are 25 years of age or older. A treatment controversy exists about the need for and timing of the removal of disease-free impacted wisdom teeth that are not causing problems. Supporters of early removal cite the increasing risks for extraction over time and the costs of monitoring the wisdom teeth that are not removed. Supporters for retaining wisdom teeth cite the risk and cost of unnecessary surgery. This condition affects up to 72% of the population. Wisdom teeth have been described in the ancient texts of Plato and Hippocrates, the works of Darwin and in the earliest manuals of operative dentistry. It was the meeting of sterile technique, radiology and anaesthesia in the late 19th and early 20th centuries that allowed the more routine management of impacted wisdom teeth. ==Classification== All teeth are classified as either developing, erupted (into the mouth), embedded (failure to erupt despite lack of blockage from another tooth) or impacted. An impacted tooth is one that fails to erupt due to blockage from another tooth. Wisdom teeth develop between the ages of 14 and 25, with 50% of root formation completed by age 16 and 95% of all teeth erupted by the age of 25. However, tooth movement can continue beyond the age of 25. Impacted wisdom teeth are classified by the direction and depth of impaction, the amount of available space for tooth eruption. and the amount soft tissue or bone (or both) that covers them. The classification structure helps clinicians estimate the risks for impaction, infections and complications associated with wisdom teeth removal. Wisdom teeth are also classified by the presence (or absence) of symptoms and disease. One review found that 11% of teeth will have evidence of disease and are symptomatic, 0.6% will be symptomatic but have no disease, 51% will be asymptomatic but have disease present and 37% will be asymptomatic and have no disease.〔 Impacted wisdom teeth are often described by the direction of their impaction (forward tilting, or mesioangular being the most common), the depth of impaction and the age of the patient as well as other factors such as pre-existing infection or the presence of pathology.〔 Of these predictors, age correlates best with extraction difficulty and complications during wisdom teeth removal rather than the orientation of the impaction. Another classification system often taught in U.S. dental schools is known as ''Pell and Gregory Classification''. This system includes a horizontal and vertical component to classify the location of third molars (predominately applicable to mandibular third molars): the third molar's relationship to the occlusal plane being the vertical or ''x-component'' and to the anterior border of the ramus being the horizontal or ''y-component''. Vertically, Class A impaction is one in which the occlusal surface of the impacted tooth is level or nearly level with the occlusal plane and the cervical line of the adjacent second molar.〔Hupp, James R., et. al. ''Contemporary Maxillofacial Surgery, 6E'', Elsevier-Mosby, 2014. ISBN=978-0-323-09177-0〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Impacted wisdom teeth」の詳細全文を読む スポンサード リンク
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