Wisdom teeth are the third molars and usually appear between the ages of 16 and 24. Wisdom teeth are commonly extracted when they affect other teeth—this impaction is colloquially known as "coming in sideways." Most people have four wisdom teeth, but it is possible to have more or fewer. Absence of one or more wisdom teeth is an example of hypodontia. Any extra wisdom teeth are referred to as supernumerary wisdom teeth.
Impacted wisdom teeth fall into one of several categories. Mesioangular impaction is the most common form (44%), and means the tooth is angled forward, towards the front of the mouth. Vertical impaction (38%) occurs when the formed tooth does not erupt fully through the gum line. Distoangular impaction (6%) means the tooth is angled backward, towards the rear of the mouth. And finally, Horizontal impaction (3%) is the least common form, which occurs when the tooth is angled fully ninety degrees forward, growing into the roots of the second molar.
Typically distoangular impactions are the easiest to extract in the maxilla and most difficult to extract in the mandible, while mesioangular impactions are the most difficult to extract in the maxilla and easiest to extract in the mandible.
Impacted wisdom teeth may also be categorized on whether they are still completely encased in the jawbone. If wisdom teeth are completely encased in the jawbone, it is a bony impaction. If the wisdom teeth have erupted out of the jawbone but not through the gumline, it is called a soft tissue impaction.
Sometimes the wisdom tooth fails to erupt completely through the gum bed and the gum at the back of the wisdom tooth extends over the biting surface, forming a soft tissue flap or lid around the tooth called an operculum. Teeth covered by an operculum can be difficult to clean with a toothbrush. Additional cleaning techniques can include using a needle-less plastic syringe to vigorously wash the tooth with moderately pressured water or to softly wash it with hydrogen peroxide.
However, debris and bacteria can easily accumulate under an operculum, which may cause pericoronitis, a common infection problem in young adults with partial impactions that is often exacerbated by occlusion with opposing 3rd or 2nd molars. Common symptoms include a swelling and redness of the gum around the eruption site, difficulty in opening the mouth, a bad odor or taste in the mouth, and pain in the general area which may also run down the entire lower jaw or possibly the neck. Untreated pericoronitis can progress to a much more severe infection.
If the operculum does not disappear, recommended treatment is extraction of the wisdom tooth. An alternative treatment involving removal of the operculum, called operculectomy, has been advocated. There is a high risk of permanent or temporary numbness of the tongue due to damage of the nerve with this treatment and it is no longer recommended as a standard treatment in oral surgery.
A wisdom tooth is extracted to correct an actual problem or to prevent problems that may come up in the future. Wisdom teeth are extracted for two general reasons: either the wisdom teeth have already become impacted, or the wisdom teeth could potentially become problematic if not extracted. Potential problems caused by the presence of properly grown-in wisdom teeth include infections caused by food particles easily trapped in the jaw area behind the wisdom teeth where regular brushing and flossing is difficult and ineffective. Such infections may be frequent, and cause considerable pain and medical danger. Another reason to have wisdom teeth removed is if the teeth have grown in improperly, causing the tongue to brush up against them. The tongue can tolerate it for a limited time, until it causes a painful sensation, to the point where the sheer pain can numb the tongue affected, and the area around it (part of the lips, and the cheek). The numbness feels similar to the feeling of anesthesia, possibly meaning a nerve can be affected by the wisdom tooth improperly growing in. Also, it is a wise choice to have wisdom teeth removed if undergoing extensive orthodontic work because once the teeth have come in they could inflict some damage on expensive straightening.
The extraction of wisdom teeth should only be performed by dental professionals with proper training and experience performing such extractions. The precise reasons why an individual’s wisdom teeth need to be extracted should be explained to them by their dentist, after an examination of their wisdom teeth which almost certainly will need to include x-rays. A panoramic x-ray (aka "panorex") is the best x-ray to view wisdom teeth and diagnose their problems.
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