The average person has thirty-two teeth by adulthood: sixteen teeth in the upper jaw (maxilla) and sixteen teeth in the lower jaw (mandible). However, the average adult mouth is developed to best hold only twenty-eight teeth. During the course of evolution, human jaws have become smaller, but the number of teeth that develop has not decreased. Therefore, there is not always enough space in the jaws for all thirty-two teeth. Often there are four additional teeth that do not develop or erupt properly. These extra teeth are our third molars, also known as our "wisdom teeth." Most adults have four wisdom teeth, one in each quadrant of the mouth (upper right, upper left, lower right, and lower left). However, it is estimated that about one quarter of the population is genetically missing one or more of their wisdom teeth.
Wisdom teeth are the last teeth to erupt in the mouth, usually during a person's late teens or early twenties. Although eruption most often occurs between the ages of 18 and 24, it is not uncommon for these third molars to erupt outside of this age range. If wisdom teeth develop normally and erupt into the mouth in proper alignment with the surrounding teeth, the teeth do not have to be removed. When inadequate space or an obstruction prevents the teeth from erupting into the proper position, they are "impacted" and extraction is necessary. Studies suggest that more than 2/3rds of the population have at least one impacted third molar.
Wisdom teeth can be found in many different positions in the jaw as they attempt to find a pathway that will allow them to erupt into the mouth. They may grow sideways, they may partially emerge from the gums, or they may remain completely trapped below the gums and bone. Trapped, or impacted, wisdom teeth can create many problems in the oral cavity if they are left untreated for years. When this occurs your dentist will recommend wisdom teeth extraction.
Classifications of Impacted Wisdom Teeth
A wisdom tooth becomes impacted either because there is not enough room in the jaw for the tooth to develop and erupt properly or because the angulation of the erupting tooth is incorrect. Impacted wisdom teeth can either be classified based on the positioning of the tooth in the jaw or on the type of impaction (soft tissue or bony). The most common dental terms used to describe the general positioning of an impacted tooth include mesio-angular, disto-angular, vertical, and horizontal.
The most common type of impacted wisdom tooth is the mesio-angular impaction. In this case the wisdom tooth is angled forward, towards the front of the mouth.
With a disto-angular impaction, the wisdom tooth is angled backwards. This is the most difficult impaction to extract.
When a third molar has a vertical impaction, the tooth is angulated properly but fails to erupt into the mouth.
With a horizontal impaction, the wisdom tooth is lying on its side, perpendicular to the normal occlusal plane of the teeth.
Wisdom teeth are also classified as either soft tissue impactions or bony impactions. A soft tissue impaction is one in which the upper portion of the tooth (the crown) has penetrated through the jawbone but has not fully erupted through the gums and is still covered by tissue. A partial bony impaction is one in which part of the crown of the wisdom tooth is still encased in the jawbone. A full bony impaction is one in which the entire wisdom tooth is completely encased in the jawbone.
Why Do We Extract Wisdom Teeth?
Many wisdom teeth need to be extracted because the gum tissues around them repeatedly become infected. This is often the case when the wisdom teeth are "partially erupted". When a tooth is partially erupted, as in a soft tissue impaction, the crown of the tooth has only partly penetrated through the gum tissue. An opening exists between the gums and the partially erupted tooth, and bacteria from inside the mouth can get underneath the gum tissue and proliferate. When the body's immune defenses are decreased, such as during periods of sickness or emotional stress, the bacteria can overwhelm the immune system and create an infection around the wisdom tooth. Known as pericoronitis, this bacterial infection is located in the tissues that surround the crown portion of a partially erupted tooth. Pericoronitis can cause swelling, pain, stiffness, and illness, and can spread to surrounding tissues. Untreated pericoronitis may even spread to the face and throat and can threaten the airway. Pericoronitis can be temporarily controlled by having a dentist or oral surgeon clean the infected area and prescribe antibiotics. However, as long as the tooth remains partially erupted and impossible to properly clean, repeated infections will occur. Therefore, removal of a partially erupted wisdom tooth is recommended.
Pericoronitis infection around wisdom tooth
Sometimes your dentist will recommend wisdom teeth extraction because decay forms on either the wisdom tooth itself or the tooth in front of it (the second molar). Wisdom teeth are often tilted or positioned in such a way that makes them very difficult to clean properly. Misaligned or impacted wisdom teeth can create a trap where bacterial plaque and debris accumulate between the wisdom tooth and the neighboring second molar. If the plaque and debris are not regularly removed, both the wisdom tooth and the second molar are at risk for developing cavities. When a cavity forms on a wisdom tooth and the dentist cannot access the decay or the tooth cannot be kept clean, the tooth will need to be extracted. It is best to extract the wisdom tooth before the decay becomes so great that both the wisdom tooth and second molar need to be extracted.
Periodontal (Gum) Disease
When a wisdom tooth is partially erupted or misaligned and cannot be properly cleansed, bacteria-laden plaque accumulates around the tooth and gums and contributes to the formation of periodontal (gum) disease. As gum disease progresses, the supporting gum tissue and bone of both the wisdom tooth and the neighboring second molar can become diseased. Therefore it is best to extract a misaligned or partially erupted wisdom tooth before damage is done to the neighboring tooth and its supporting structures.
If an impacted wisdom tooth is attempting to erupt but is misdirected and is leaning on the neighboring second molar, this can cause the roots of the second molar tooth to resorb (break away or lose substance). This is very damaging to the second molar and can lead to the extraction of both the wisdom tooth and the second molar.
While it is a rare occurrence, it is possible for cysts to develop in the tissues that surround an impacted wisdom tooth. These cysts can become very large and can distort the face. If they grow they can weaken the jawbone, making it more prone to fracture. If you decide not to remove an impacted wisdom tooth, your dentist or oral surgeon may want to take periodic x-rays to monitor the tooth to ensure a cyst is not forming over time.
Another very rare complication arising from an impacted wisdom tooth is the development of a tumor called an amyloblastoma. This tumor can grow to be very large, invading the jawbone and causing damage and weakness to the bone. It is more frequently seen in adult males. Amyloblastomas are difficult to remove and usually require a large portion of the jawbone to be removed. If you decide not to extract an impacted wisdom tooth, your dentist or oral surgeon may want to periodically take x-rays to evaluate the tooth to ensure an amyloblastoma is not developing.
Should all wisdom teeth be extracted?
Not all wisdom teeth need to be extracted. If wisdom teeth develop normally and erupt into the mouth in proper alignment with the surrounding teeth, they do not have to be removed. In fact, not even all impacted teeth must be removed. Many people have impacted wisdom teeth their entire lives and never experience complications. A dentist or oral surgeon uses his or her judgment and experience to determine which impacted wisdom teeth are at risk for developing problems and recommends extraction of these high risk teeth.
Partially erupted wisdom teeth are the most likely impactions to become problematic and usually require extraction. When a tooth is partially erupted, the crown of the tooth has only partly penetrated through the gum tissues. An opening exists between the gums and the partially erupted tooth, and bacteria from inside the mouth can get underneath the gum tissue and proliferate. This places the tooth at risk for complications, especially pericoronitis, tooth decay, and periodontal disease.
Full bony impactions (where the wisdom teeth are fully encased in the jawbone) are the type of impaction least likely to cause complications. However, these teeth should be monitored by your dentist and extracted if evidence of a cyst, tumor, or other pathology begins to form.
There are other complicating factors associated with the patient or the tooth that may be contraindications to wisdom teeth extractions. For example, immunocompromised patients or those patients with serious underlying illnesses are rarely candidates for wisdom teeth extractions. Patients on bisphosphonate therapy, anticoagulant therapy, or those with bleeding disorders may not be candidates for wisdom teeth extractions. Furthermore, teeth that lie in very close proximity to the mandibular nerve (a major nerve that runs through the lower jaw) are often left alone because removal of these teeth could lead to post-operative numbness if the nerve is damaged during the extraction.
All retained wisdom teeth should be monitored regularly. A problem can arise at any time, and even the position of a wisdom tooth in the jawbone can change over time. Wisdom teeth should be routinely examined and x-rayed by your dentist. The best way to monitor wisdom teeth that are not scheduled for extraction is with a digital panoramic x-ray. A digital panoramic x-ray will expose the patient to less radiation than a traditional film based panoramic x-ray .
At what age should wisdom teeth be extracted?
Early extraction of wisdom teeth is recommended to avoid the complications associated with both the impaction itself and the extraction of the tooth. The problems associated with impacted wisdom teeth tend to occur more frequently in adults over the age of 30. Wisdom teeth are also more difficult to remove in adults because the roots are longer and the jawbone is denser. Furthermore, older patients tend to experience more complications with post-operative recovery and healing. Younger patients tend to experience fewer complications with third molar extractions. Therefore, the best time to have wisdom teeth removed is during the teenage years or early twenties before the root structure is fully developed and before any complications arise.
What Is dry socket?
The most common complication associated with a wisdom tooth extraction is known as dry socket. A dry socket is a condition that can develop over the first several days following an extraction. A dry socket develops when either a blood clot has failed to form in the extracted tooth's socket or the blood clot that did form has dislodged. Loss of a blood clot disturbs the healing of the bone in the socket.
Symptoms of a dry socket typically include a dull, throbbing pain that is moderate to severe and begins three to four days following an extraction. There is also often a foul odor or taste coming from the socket. Dry sockets are more likely to develop after the extraction of lower wisdom teeth and are more common following surgical extractions (as opposed to simple or non-surgical extractions). Dry sockets are treated with a soothing, medicated dressing.
We understand that some patients are very nervous about extracting their wisdom teeth. Therefore we offer different levels of sedation to provide total comfort to our apprehensive patients. By using nitrous oxide or oral conscious sedation, we are able to comfortably treat our fearful patients in a beautiful and tranquil operatory. With some sedation the patient will have very little if any memory of the wisdom teeth extraction procedure.
If you need to have your wisdom teeth extracted, please contact the Kurpis Center for Advanced Dentistry at 201-447-9700.