There is ongoing debate regarding the need to extract wisdom teeth. Numerous scientific publications have aimed to clarify when it is medically appropriate to extract wisdom teeth, while many non-surgeons and patients have argued that there are too many unnecessary extractions. A recent article in The New York Times again raised the question of the value of wisdom teeth extraction. The author provided no clinical information about her daughter's case but used it as an example of yet another patient who was misled into thinking that "her wisdom teeth had to come out, A.S.A.P." (1) This kind of criticism is nothing new to the medical community: Last year, President Obama suggested that otolaryngologists frivolously remove young people's tonsils. (2) Obama quickly retracted his statement, but when critics perpetuate these unfortunate stereotypes, it makes the job of responsible and fair doctors that much harder.
The information below is intended to help patients evaluate the indications for wisdom teeth extraction. Much of this information is based on the "White Paper on Third Molar Data" published by the American Association of Oral and Maxillofacial Surgeons, which reviewed the current literature published on wisdom teeth and their removal.
Several factors need to be considered when evaluating wisdom teeth: The health of the second molar, the presence of gum disease, the age of the patient and the risk of dental crowding. To minimize the possibility of negative outcomes, the use of cone beam imaging will also be discussed.
The Health of the Second Molar
Adults have 32 teeth in their mouth, which includes the second molars, located immediately in front of the wisdom teeth. When evaluating wisdom teeth, it is important to evaluate the health of the second molars to make sure they are not compromised by the position of the wisdom teeth. Wisdom teeth can grow in a variety of positions: Sometimes they erupt straight up like the rest of the teeth, but other times they will grow sideways or toward the second molars, encroaching on their space. Research has shown that the ligament surrounding the second molars and its roots can be negatively affected by wisdom teeth, especially as one gets older. (3)
When these conditions are already present, they improve with time after removal of the wisdom teeth, but it is important to note that the outcome correlates with the age of the patient and the level of plaque present in the mouth. For example, a teenager with impacted wisdom teeth and plaque buildup around the second molars will probably do well after the wisdom teeth are removed, but an older patient in in his 30s may have a bone or gum defect behind the second molars after the wisdom teeth are extracted.
Gum Disease and Wisdom Teeth
Another factor to evaluate is the pocket depth measurement behind the second molars. A pocket depth of 5mm or more can compromise the second molars. (4) These pocket depths have been shown to increase over time, and bacteria associated with gum disease have been found in these gum pockets, suggesting that impacted wisdom teeth can have a detrimental effect on the health of the gums. (5) (6) Notably, the bacteria count around the molars has been shown to decrease after removal of wisdom teeth. (7)
After extraction of wisdom teeth, some surgeons have advocated bone grafting to improve the outcome of the second molar. This does appear to offer an advantage in preventing a defect behind the second molar, but only in adults 26 years of age or older with a pre-existing attachment loss and an impacted and mal-positioned wisdom tooth that is severely compromising the second molar. (8)
It is also important to note the effect of wisdom teeth on gum disease and inflammation, which has been linked to a negative systemic impact on pregnancy outcomes in women with asymptomatic retained wisdom teeth. (9) In short, the presence of wisdom teeth tends to cause inflammation, which can negatively impact physical health, including pregnancy outcomes.
Age & Wisdom Teeth
Numerous studies have shown that older adults have a higher risk of having a periodontal defect on the second molar when wisdom teeth are present. (10) The incidence of cavities on wisdom teeth also increases with age. (11) As far as complications after surgery, the risks of post-op complications and recovery time both increase with age, especially in patients 25 years of age and older. (12) Interestingly, early removal of wisdom teeth (when the teeth have hardly any of the roots formed) has been shown to result in very predictable and successful outcomes, with hardly any gum pockets, dry sockets, nerve injury or infections developing post-operatively. (13) Alternatively, it is well documented that there is increased difficulty and an increased risk of complications when removing wisdom teeth later in life. (14)
Wisdom Teeth and Dental Crowding
While patients and dentists are always quick to blame wisdom teeth for dental crowding, a definitive and clear correlation between wisdom teeth and dental crowding is difficult to confirm or exclude. Dental crowding is caused by a variety of conditions, and while wisdom teeth may play a significant role in some patients, a direct effect has not been established.
Wisdom Teeth and CT Imaging
Traditionally, wisdom teeth have been evaluated by obtaining a panoramic x-ray, which gives an excellent preliminary evaluation of someone's jaws to detect the presence of wisdom teeth, their position and to evaluate for the presence of any cysts or other pathology. But panoramic x-rays give the clinician only a limited view, thereby limiting the amount of specificity and detail available to properly plan and prepare for an actual surgery due to distortions present in the image. A cone beam scan, however, is similar to a medical CT scan, in that it allows the clinician to view very minute details in a three-dimensional view, take specific measurements and look at individual slices of an area of interest.
When planning the removal of wisdom teeth, one important consideration is the position of the mandibular nerve in relation to the roots of the wisdom teeth. This nerve often runs in very close proximity to the wisdom teeth, and injury to that nerve can cause temporary or permanent numbness of the chin or lower lip. While research suggests that the immediate risk of numbness after surgery is between 1 and 5 percent, and persistent numbness six months after surgery is less than 1 percent, it is always desirable to minimize the risk of any complications during surgery. (15) (16)
A cone beam scan will allow the clinician to evaluate the position of the nerve in very fine detail, evaluate the position of the second molar and allow the surgeon to carefully plan the surgery. An analogy would be to a lung surgeon who surgically removes a mass in someone's lungs using solely a chest x-ray rather than a CAT scan. The scan would allow the lung surgeon to figure out exactly the location and size of the lesion in order to minimize the risk of complications and trauma to the surrounding healthy tissue. Similarly, the oral surgeon takes advantage of the current advances in technology to properly plan a safe surgery for patients. While the level of radiation exposure is always a cause for concern anytime someone gets an x-ray, it's important to note that cone beam scans can deliver as little as 0.087mSv of radiation, which is comparable to natural radiation exposure for 11 days (in contrast, a medical CT of the skull delivers about 0.86mSv of radiation, which is comparable to natural radiation exposure for 108 days). (17)
While all patients do not need to have their wisdom teeth extracted, there are clear indications that warrant removal of wisdom teeth. The age of the patient, the presence of gum disease, the potential for dental crowding and the long-term health of the second molars are all factors that must be considered when deciding if the wisdom teeth need to be extracted.
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(3) Stanley HR, Alattar M, Collett WK et al.: Pathological sequelae of "neglected" impacted third molars. J Oral Pathol Med 17:113, 1988; Nemcovsky C, Libfeld H, Zubery Y: Effect of non-erupted 3rd molars on distal roots and supporting structures of approximal teeth. A rediographic survey of 202 cases. J Clin Periodont 23:810, 1996; Knutsson K, Brehmer B, Lysell L, Rohlin M: Pathoses associated with mandibular third molars subjected to removal. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 82:10, 1996.
(4) Blakey GH, Marciani RD, Haug RH et al.: Periodontal pathology associated with asymptomatic third molars. J Oral Maxillofac Surg 60:1227, 2002
(5) White RP, Jr., Offenbacher S, Blakey GH et al.: Chronic Oral Inflammation and the Progression of Periodontal Pathology in the Third Molar Region. J Oral Maxillofac Surg 64:880, 2006
(6) White RP, Jr., Madianos PN, Offenbacher S et al.: Microbial complexes detected in the second/third molar region in patients with asymptomatic third molars. J Oral Maxillofac Surg 60:1234, 2002
(7) Blakey GH, Jacks MT, Offenbacher S et al.: Progression of periodontal disease in the second/third molar region in subjects with asymptomatic third molars. J Oral Maxillofac Surg 64:189, 2006
(8) Dodson T: Management of mandibular third molar extraction sites to prevent periodontal defects. J Oral Maxillofac Surg 62:1213, 2004; Dodson T: Is there a role for reconstructive techniques to prevent periodontal defects after third molar surgery. J Oral Maxillofac Surg 63:891, 2005
(9) Moss KL, Mauriello S, Ruvo AT et al.: Reliability of third molar probing measures and the systemic impact of third molar periodontal pathology. J Oral Maxillofac Surg 64:652, 2006
(10) Elter JR, Offenbacher S, White RP, Jr., Beck JD: Third molars associated with periodontal pathology in older Americans. J Oral Maxillofac Surg 63:179, 2005; Moss KL, Beck JD, Mauriello SM et al.: Third molar periodontal pathology and caries in senior adults. J Oral Maxillofac Surg 65:103, 2007
(11) Moss KL, Beck JD, Mauriello SM et al.: Third molar periodontal pathology and caries in senior adults. J Oral Maxillofac Surg 65:103, 2007; Shugars DA, Jacks MT, White RP, Jr. et al.: Occlusal caries experience in patients with asymptomatic third molars. J Oral Maxillofac Surg 62:973, 2004; Shugars DA, Elter JR, Jacks MT et al.: Incidence of occlusal dental caries in asymptomatic third molars. J Oral Maxillofac Surg 63:341, 2005
(12) Mercier P, Precious D: Risks and benefits of removal of impacted third molars. A critical review of the literature. Int J Oral Maxillofac Surg 21:17, 1992; Bruce RA, Frederickson GC, Small GS: Age of patients and morbidity associated with mandibular third molar surgery. J Am Dent Assoc 101:240, 1980; Phillips C, White RP, Jr., Shugars DA, Zhou X: Risk factors associated with prolonged recovery and delayed healing after third molar surgery. J Oral Maxillofac Surg 61:1436, 2003; Bui CH, Seldin EB, Dodson TB: Types, frequencies, and risk factors for complications after third molar extraction. J Oral Maxillofac Surg 61:1379, 2003
(13) Chiapasco M, Crescentini M, Romanoni G: Germectomy or delayed removal of mandibular impacted third molars: the relationship between age and incidence of complications. J Oral Maxillofac Surg 53:418, 1995; Chossegros C, Guyot L, Cheynet F et al.: Is lingual nerve protection necessary for lower third molar germectomy? A prospective study of 300 procedures. Int J Oral Maxillofac Surg 31:620, 2002;
(14) Chiapasco M, Crescentini M, Romanoni G: [The extraction of the lower third molars: germectomy or late avulsion?] [article in Italian]. Minerva Stomatol 43:191, 1994; Bruce RA, Frederickson GC, Small GS: Age of patients and morbidity associated with mandibular third molar surgery. J Am Dent Assoc 101:240, 1980
(15) Gulicher D, Gerlach KL: Sensory impairment of the lingual and inferior alveolar nerves following removal of impacted mandibular third molars. International Journal of Oral and Maxillofacial Surgery 30:306, 2001; Schultze-Mosgau S, Reich RH: Assessment of inferior alveolar and lingual nerve disturbances afterdentoalveolar surgery, and of recovery of sensitivity. International Journal of Oral and Maxillofacial Surgery 22:214, 1993
(16) Queral-Godoy E, Valmaseda-Castellon E, Berini-Aytes L, Gay-Escoda C: Incidence and evolution of inferior alveolar nerve lesions following lower third molar extraction. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 99:259, 2005; Valmaseda-Castellon E, Berini-Aytes L, Gay-Escoda C: Inferior alveolar nerve damage after lower third molar surgical extraction: a prospective study of 1117 surgical extractions. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 92:377, 2001
(17) Imaging Sciences International letter from Henrik Roos, dated November 23, 2010
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