Wisdom tooth

Wisdom teeth are third molars that usually appear between the ages of 17 and 24 (although they may appear when older, younger, or may not appear at all). They are commonly removed when they affect other teeth— this impaction is colloquially known as "coming in sideways."

Wisdom teeth are an example of a vestigial structure, [1] Some argue that recent changes to softer diets which cause less wear on the teeth may be causing the third molars to be less useful, and, in fact, problematic in many humans. Alternatively, it is possible that wisdom teeth were useful when it was common for humans to lose several teeth to decay by the age when they appear.

Although most people have four wisdom teeth, it is possible to have more or fewer. Absence of one or more wisdom teeth is an example of hypodontia. Any extra teeth are referred to as supernumerary teeth. [2] [3]

Etymology

They are generally thought to be called wisdom teeth because they appear so late—much later than the other teeth, at an age where people are supposedly wiser than as a child, when the other teeth erupt. English wisdom tooth, German Weisheitszahn, Dutch verstandskies, French dents de sagesse.

Impactions

The upper left (picture right) and upper right (picture left) wisdom tooth are distoangularly impacted. The lower left wisdom tooth is horizontally impacted. The lower right wisdom tooth is vertically impacted (unidentifiable in X-ray image).

Impacted wisdom teeth fall into one of several categories. Mesioangular impaction is the most common form, and means the tooth is angled forward, towards the front of the mouth. Vertical impaction occurs when the formed tooth does not erupt fully through the gumline. Horizontal impaction occurs when the tooth is angled fully ninety degrees forward, growing into the roots of the second molar. Finally, distoangular impaction is the least common form, and means the tooth is angled backward, towards the rear of the mouth. Typically distoangular and vertical impactions are the most difficult types of wisdom teeth to extract.

Impacted wisdom teeth may also be categorized on whether they are still completely encased in the jawbone. If it is completely encased in the jawbone, it is a bony impaction. If the wisdom tooth has erupted out of the jawbone but not through the gumline, it is called a soft tissue impaction.

Sometimes the wisdom tooth has failed 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, it may be necessary to trim the soft tissue in a procedure called an operculectomy. If it reoccurs along with pericoronitis, it may be necessary to extract the wisdom tooth.

Extraction

An extracted wisdom tooth that was horizontally impacted.

Main article: Extraction (dental)

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 not effective. Such infections may be frequent, and cause considerable pain and medical danger. The extraction of wisdom teeth can be a difficult surgical procedure, and should only be performed by dental professionals with proper training and experience performing such extractions.

Post-extraction problems

There are several problems that can manifest themselves after the extraction(s) have been completed. Some of these problems are unavoidable and natural, while others are under the control of the patient. The suggestions contained in the sections below are general guidelines that a patient will be expected to abide by, but the patient should follow all directions that are given by the surgeon in addition to the following guidelines. Above all, the patient must not disregard the given instructions; doing so is extremely dangerous and could result in any number of problems ranging in severity from being merely inconvenient (dry socket) to potentially life-threatening (serious infection of the extraction sites).

Bleeding and oozing

Bleeding and oozing is inevitable and should be expected to last up to a day. Rinsing out one's mouth during this period is counter-productive, as the bleeding stops when the blood forms clots at the extraction sites, and rinsing out the mouth will most likely dislodge the clots. The end result will be a delay in healing time and a prolonged period of bleeding. Gauze pads should be placed at the extraction sites, and then should be bitten down on with firm and even pressure. This will help to stop the bleeding, but should not be overdone as it is possible to irritate the extraction sites and prolong the bleeding. The bleeding should decrease gradually and noticeably upon changing the gauze. If the bleeding lasts for more than a day without decreasing despite having followed the surgeon's directions, the surgeon should be contacted as soon as possible. This is not supposed to happen under normal circumstances and signals that a serious problem is present.

Due to the blood clots that form in the exposed sockets as well as the abundant bacterial flora in the mouth, an offensive smell may be noticeable a short time after surgery. This is to be expected and will diminish over an indefinite amount of time, although one to two weeks is normal. However, a persistent bad smell often is accompanied by an equally rancid-tasting fluid seeping from the wounds. While not a cause for great concern, a post-operative appointment with your surgeon seven to ten days after surgery is highly recommended to make sure that the healing process has no complications and that the wounds are relatively clean. A plastic syringe (minus the hypodermic needle) full of a mixture of equal parts hydrogen peroxide and water should be gently plunged into the sockets to remove any food or bacteria that may collect in the back of the mouth.

Dry socket

Main article: dry socket

A dry socket is the event where the blood clot at an extraction site is dislodged or falls out prematurely or fails to form. In some cases, this is beyond the control of the patient. However, in other cases this happens because the patient has disregarded the instructions given by the surgeon. Smoking, spitting or drinking with a straw in disregard to the surgeon's instructions can cause this. The extraction site will become irritated and pain will manifest at one level or another. The patient should contact their surgeon if they suspect that they have a case of dry socket; the surgeon can prescribe medication in topical form to apply to the affected site. If this is done, dry socket becomes merely an annoyance, but without the medication dry socket can progress to an infection of the extraction site.

Swelling

Swelling should not be confused with dry socket; although painful, swelling should be expected and is a sign that the healing process is progressing normally. There is no general duration for this problem; the severity and duration of the swelling vary from case to case. The instructions the surgeon gives the patient will tell the patient for how long they should expect swelling to last, including when to expect the swelling to peak and when the swelling will start to subside. If the swelling does not begin to subside when it is supposed to, the patient should contact their surgeon immediately. While the swelling will generally not disappear completely for several days after it peaks, swelling that does not begin to subside or gets worse may be an indication of infection. Swelling that re-appears after a few weeks is an indication of infection caused by a bone or tooth fragment still in the wound and should be treated immediately.

Nerve injury

This is primarily an issue with extraction of third molars, however, can technically occur with the extraction of any tooth should the nerve be in close proximity to the surgical site. Two nerves are typically of concern, and are found in duplicate (one left and one right side): 1. the inferior alveolar nerve, which enters the mandible at the mandibular foramen and exits the mandible at the sides of the chin from the mental foramen. This nerve supplies sensation to the lower teeth on the right or left half of the dental arch, as well as sense of touch to the right or left half of the chin and lower lip. 2. The lingual nerve (one right and one left side), which branches off the mandibular branches of the trigeminal nerve and courses just inside the jaw bone, entering the tongue and supplying sense of touch and taste to the right and left half of the anterior 2/3 of the tongue as well as the lingual gingiva (i.e. the gums on the inside surface of the dental arch). Such injuries can occur while lifting teeth (typically the inferior alveolar), but are most commonly caused by inadvertent damage with a surgical drill. Such injuries are rare and are usually temporary, but depending on the type of injury (i.e. Seddon classification: neuropraxia, axonotmesis, and neurotmesis), can be prolonged or even permanent.

Cyst around right lower wisdom tooth.

Controversy

Preventative removal of the third molars is a common practice in developed countries despite the lack of scientific data to support this practice. In 2006, the Cochrane Collaboration published a review[4] designed to evaluate the effect of preventative removal of asymptomatic wisdom teeth. The authors found no evidence to either support or refute this practice. However, there was reliable evidence showing that preventative removal did not reduce or prevent late incisor crowding. The authors of the review suggested that the number of surgical procedures could be reduced by 60 percent or more.

External links

• Wisdom teeth informedhealthonline.org
• University of Manitoba Dental Hygene Article on wisdom teeth.