Tooth-extraction complications - Oral paresthesia (nerve damage).
What is oral paresthesia?
One of the potential complications associated with wisdom tooth removal is paresthesia. Paresthesia refers to a situation where postoperatively a patient experiences altered sensation due to nerve trauma or damage sustained during their oral surgery.
Why does it happen?
In regards to wisdom tooth extractions, a patient's risk for experiencing paresthesia is related to the positional relationship between their tooth its associated nerves.
If a nerve lies in relative close proximity to the tooth (or close to or in the tissues around the tooth that must be manipulated during the extraction process) then there is potential that it may become bruised or damaged during their surgery.
Which nerves are typically affected?
The nerves that typically placed at greatest risk during wisdom tooth removal are the mandibular and lingual nerves.
The mandibular nerve runs within the lower jaw (both right and left half), in the neighborhood of the tip of the roots of the lower teeth. It then ultimately branches out and runs to the lip and chin.
The lingual nerve, actually a branch of the mandibular nerve, runs in the soft tissue on the tongue side of the lower jaw and ultimately courses on to the tongue.
What does having paresthesia feel like?
Usually paresthesia is a strictly "sensory" phenomenon. The person experiences a loss of sensation (touch, pain, proprioception, temperature or taste) it is not accompanied by any type of paralysis.
For most people, the sensation of having paresthesia is similar to what they experience when they have a tooth "numbed up" with anesthetic ("novocaine"). The difference being that the sensation persists. In most cases, the area affected by the paresthesia is the person's lip, chin or tongue (the tissues innervated by the mandibular and lingual nerves).
How long does paresthesia last?
Fortunately, in most cases a person's paresthesia will resolve on its own after just a few days or weeks. However, there can be cases where a person's paresthesia can be classified as being "persistent" (lasting longer than 6 months). In a small number of cases, a person's paresthesia can be permanent.
Risk factors for wisdom tooth-related paresthesia.
A) Location, location, location.
Studies have shown that the risk of experiencing paresthesia is greatly dependent upon the specific tooth being extracted and its particular anatomical positioning. Lower wisdom teeth are much more likely to be associated with paresthesia than upper ones (due to their close proximity to the mandibular and lingual nerves).
Lower full-bony impactions are the type of extraction most likely to be associated with a risk of paresthesia of the mandibular nerve. Any lower wisdom tooth angled or positioned relatively closer to the tongue-side of the jawbone places the lingual nerve at greater risk for trauma during surgery.
B) Surgical factors.
Research has demonstrated that the practitioner's experience, the surgical technique they use, and the overall duration of the extraction process all play a role in how much risk exists for any one patient to experience paresthesia. This is one reason why many dentists will choose to refer potentially challenging wisdom tooth extractions to an oral surgeon.
C) Age can be a risk factor for paresthesia.
After the age of 25 years, a person's risk for experiencing paresthesia typically increases. Relatively "older" patients (those over the age of 25 years and especially over the age of 35 years) typically have more completely formed wisdom tooth roots and denser surrounding bone. Both of these factors increase the difficulty of performing the tooth's extraction without disturbing its surrounding tissues.
A risk for paresethesia can be one reason why asymptomatic full-bony impacted wisdom teeth that show no sign of associated pathology are often left alone in people over the age of 35 years.
How likely is it a person will experience paresthesia after a third molar extraction?
A literature review performed by Blondeau (2007) found reported rates for paresthesia after wisdom tooth removal ranging from 0.4% and 8.4%. A large study involving the extraction of over 8,000 third molars (Haug 2005) found an incidence rate of less than 2% in a study group of patients age 25 years and older (a group expected to be at relatively at-risk for paresthesia).
How long can paresthesia be expected to last?
In most cases, a patient's paresthesia will resolve on it's own over time. This can, however, can take several months to over a year. In some cases, a person's paresthesia is permanent.
Most recoveries take place within the first 3 months after the person's wisdom tooth extraction. At 6 months, one-half of all of those affected experience a full recovery (Queral-Godoy, 2005).
Persistent paresthesia is typically classified as altered sensation that lasts longer than 6 months. Pogrel's (2007) review of dental literature reported an incidence rate of persistent paresthesia ranging between 0% and 0.9% for the mandibular nerve and 0% and 0.5% for the lingual nerve. (These numbers aren't for those populations who experienced paresthesia but instead a percentage of all people who had a wisdom tooth extracted.)
If paresthesia persists, is treatment possible?
For those who experience persistent paresthesia, it may be possible to attempt some type of surgical repair. In most cases, this approach is not taken until 6 to 12 months after the original injury (it can be performed even later). The reported results for surgical intervention (Pogrel, 2007) vary widely. Success rates appear to range between 50% and 92%. These successes, however, are typically stated in terms such as "produced some recovery."