impacted wisdom teeth impacted wisdom teeth impacted wisdom teeth is a condition where the third molars (wisdom teeth) are prevented from erupting into the mouth. this can be caused by a physical barrier, such as other teeth, or when the tooth is angled away from a vertical position. completely unerupted wisdom teeth usually result in no symptoms, although they can sometimes develop cysts or neoplasms. partially erupted wisdom teeth can develop cavities or pericoronitis. removal of impacted wisdom teeth is advised in the case of certain pathologies, such as nonrestorable caries or cysts. impacted wisdom teethother namesimpacted third molars3d ct of an impacted wisdom tooth adjacent the inferior alveolar nerve prior to removal of wisdom toothspecialtydentistry, oral and maxillofacial surgerysymptomslocalized pain and swelling behind the last teethcomplicationsinfections, loss of adjacent teeth, cystsusual onsetlate teens, early 20stypesfull vs partially impacted, direction of impactioncausescongenitaldiagnostic methodexamination, x-raydifferential diagnosisother causes for dental pain, tmj paintreatmentgood dental care, removal of wisdom teethfrequency70-75% of the population 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 a 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 surgical removal of the gum overlying the tooth. over time, most of these treatments tend to fail and patients develop recurrent symptoms. the most common treatment for recurrent pericoronitis 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. supporters of early removal cite the increasing risks for extraction over time and the costs of monitoring the wisdom teeth. supporters for retaining wisdom teeth cite the risk and cost of unnecessary surgery. the condition affects up to 72% of the swedish 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 anesthesia 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. impacted teeth are ones that fail to erupt due to blockage from other teeth. wisdom teeth, as the last teeth to erupt in the mouth are the most likely to become impacted. they 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, some tooth movement can continue beyond the age of 25.: 140 impacted wisdom teeth are classified by the direction and depth of impaction, the amount of available space for tooth eruption, and the amount of 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 wisdom 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 (cysts, tumors or other disease).: 143–144 each of these factors is used to predict the difficulty (and rate of complications) when removing an impacted tooth, with age being the most reliable predictor rather than the orientation of the impaction.impacted wisdom tooth with a backward tilt (distoangular impaction) and chronic infection to back of crown (green arrow)impacted wisdom tooth with no tilt (vertical impaction)impacted wisdom tooth that is tilted forward (mesioangular impaction)impacted wisdom tooth with a horizontal orientation (horizontal 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 lower third molars): the third molar's relationship to the level of the teeth already in the mouth, being the vertical or x-component and to the anterior border of the ramus being the horizontal or y-component. signs and symptoms pericoronitis (green arrow) in lower right wisdom tooth impacted wisdom teeth without communication to the mouth, that have no pathology associated with the tooth, and have not caused tooth resorption on the blocking tooth, rarely have symptoms. the chances of developing pathology on an impacted wisdom tooth that is not communicating with the mouth is approximately 12%. however, when impacted wisdom teeth communicate with the mouth, food and bacteria penetrate to the space around the tooth and cause symptoms such as localized pain, swelling and bleeding of the tissue overlying the tooth. the tissue overlying the tooth is called the operculum, and the disorder is called pericoronitis which means inflammation around the crown of the tooth.: 141 low grade chronic periodontitis commonly occurs on either the wisdom tooth or the second molar, causing less obvious symptoms such as bad breath and bleeding from the gums. the teeth can also remain asymptomatic (pain free), even with disease. the term asymptomatic means that the person has no symptoms. the term asymptomatic should not be equated with absence of disease. most diseases have no symptoms early in the disease process. a pain-free or asymptomatic tooth can still be infected for many years before pain symptoms develop. causes wisdom teeth become impacted when there is not enough room in the jaws to allow for all of the teeth to erupt into the mouth. because the wisdom teeth are the last to erupt, due to insufficient room in the jaws to accommodate more teeth, the wisdom teeth become stuck in the jaws, i.e., impacted. there is a genetic predisposition to tooth impaction. genetics plays an important, albeit unpredictable role in dictating jaw and tooth size and tooth eruption potential of the teeth. some also believe that there is an evolutionary decrease in jaw size due to softer modern diets that are more refined and less coarse than our ancestors'. pathophysiology impacted wisdom tooth with caries and cyst (green arrow) displacing inferior alveolar nerve (blue) impactions completely covered by bone and soft tissue, do not communicate with the mouth, and have a low rate of clinically significant infection. since the tooth never erupts, however, the dental follicle that surrounds the tooth does not degenerate during eruption, and can develop cysts or uncommon tumors over time.: 141 estimates of the incidence of cysts or other neoplasms (almost all benign) around impacted teeth average at 3%, usually seen in people under the age of 40. this suggests that the chance of tumor formation decreases with age.: 141 bacteroides fragilis bacteria under microscope for partially impacted teeth in those over 20 year of age, the most common pathology seen, and the most common reason for wisdom teeth removal, is pericoronitis or infection of the gum tissue over the impacted tooth. the bacteria associated with infections include peptostreptococcus, fusobacterium, and bacteroides bacteria. the next most common pathology seen is cavities or tooth decay. fifteen percent of people with retained wisdom teeth exposed to the mouth have cavities on the wisdom tooth or adjacent second molar due to a wisdom tooth. the rate of cavities on the back of the second molar has been reported anywhere from 1% to 19% with the wide variation attributed to increased age. in five percent of cases, advanced periodontitis or gum inflammation between the second and third molars precipitates the removal of wisdom teeth.: 141 among patients with retained, asymptomatic wisdom teeth, roughly 25% have gum infections (periodontal disease).: ch13 teeth with periodontal pockets of greater than 5mm have tooth loss rates that start at 10 teeth lost per 1000 teeth per year at 5mm to a rate of 70 teeth lost per year per 1000 teeth at 11mm.: 57 the risk of periodontal disease and caries on third molars increases with age with a small minority (less than 2%) of adults age 65 years or older maintaining the teeth without caries or periodontal disease and 13% maintaining unimpacted wisdom teeth without caries or periodontal disease. periodontal probing depths increase over time to greater than 4 mm in a significant proportion of young adults with retained impacted wisdom teeth which is associated with increases in serum inflammatory markers such as interleukin-6, soluble intracellular adhesion molecule-1 and c-reactive protein. crowding of the front teeth is not believed to be caused by the eruption of wisdom teeth although this is a reason many dental clinicians use to justify wisdom teeth extraction.: 141 , diagnosis panoramic radiograph of impacted lower wisdom teeth (green arrows) in a 26-year-old with dental caries (red arrows) on the adjacent teeth the diagnosis of impaction can be made clinically if enough of the wisdom tooth is visible to determine its angulation, depth, and if the patient is old enough that further eruption or uprighting is unlikely. wisdom teeth continue to move to the age of 25 years old due to eruption, and then continue some later movement owing to periodontal disease. if the tooth cannot be assessed with clinical exam alone, the diagnosis is made using either a panoramic radiograph or cone-beam ct. where unerupted wisdom teeth still have eruption potential several predictors are used to determine the chance of the teeth becoming impacted. the ratio of space between the tooth crown length and the amount of space available, the angle of the teeth compared to the other teeth are the two most commonly used predictors, with the space ratio being the most accurate. despite the capacity for movement into early adulthood, the likelihood that the tooth will become impacted can be predicted when the ratio of space available to the length of the crown of the tooth is under 1.: 141 screening impacted 2nd molar (red arrow) with developing wisdom tooth (green arrow) there is no standard to screen for wisdom teeth. it has been suggested, absent evidence to support routinely retaining or removing wisdom teeth, that evaluation with panoramic radiograph, starting between the ages of 16 and 25 be completed every 3 years. once there is the possibility of the teeth developing disease, then a discussion about the operative risks versus long-term risk of retention with an oral and maxillofacial surgeon or other clinician trained to evaluate wisdom teeth is recommended. these recommendations are based on expert opinion level evidence. screening at a younger age may be required if the second molars (the "12-year molars") fail to erupt as ectopic positioning of the wisdom teeth can prevent their eruption. radiographs can be avoided if the majority of the tooth is visible in the mouth. treatment wisdom teeth that are fully erupted and in normal function need no special attention and should be treated just like any other tooth. it is more challenging, however to make treatment decisions with asymptomatic, disease-free wisdom teeth where there is a high probability that the teeth will develop disease over time, but none exists on examination, or on x-rays (see treatment