Wisdom teeth are the final set of teeth to emerge, usually appearing in the late teenage years or early twenties. For many, the jaw lacks sufficient space to accommodate them, resulting in the teeth becoming partially or fully trapped within the gum tissue or jawbone, a condition called impaction. Leaving these teeth in place, particularly when they are impacted or misaligned, can lead to consequences. The outcome of non-removal depends heavily on the tooth’s position and overall health, and this article explores the specific dental and structural problems that can develop when third molars are retained.
Pericoronitis and Increased Risk of Decay
The most frequent immediate consequence of retaining a partially erupted wisdom tooth is the development of pericoronitis. This condition is the inflammation and infection of the soft gum tissue covering the tooth’s crown. The partial eruption creates a small space between the tooth and the overlying gum flap where food debris and plaque easily become trapped.
The environment under this gum flap is difficult to clean with standard brushing and flossing, allowing bacteria to multiply rapidly. This leads to an infection characterized by localized swelling, throbbing pain, and often a foul taste or odor due to the presence of pus. While episodes of pericoronitis can be temporarily resolved with antibiotics and professional cleaning, the condition is highly prone to recurrence unless the tissue flap or the tooth itself is ultimately removed.
Beyond soft tissue infection, the awkward positioning of a retained wisdom tooth significantly increases the risk of dental decay. When the tooth is partially covered or angled incorrectly, it is virtually impossible to maintain adequate hygiene in that far back region of the mouth. This poor cleanability allows cavity-causing bacteria to thrive on the surface of the third molar.
Untreated decay in the wisdom tooth can progress rapidly. Furthermore, the constant accumulation of plaque in this area does not only affect the wisdom tooth; it also creates a high-risk zone for the adjacent second molar. The decay mechanism involves bacterial transfer and the physical difficulty of cleaning the contact point between the two molars.
Structural Damage to Adjacent Molars
A retained, impacted wisdom tooth poses a direct physical threat to the health and integrity of the adjacent second molar. One form of damage is external root resorption, where the pressure exerted by the impacted third molar causes the root structure of the second molar to slowly dissolve. This process is often asymptomatic and can only be reliably detected through routine dental X-rays.
External root resorption occurs on approximately one-third of second molars situated next to impacted third molars. The risk is significantly higher when the wisdom tooth is in a mesioangular or angled position and maintains close proximity or direct contact with the second molar’s root. If the resorption is severe and left unaddressed, it can compromise the stability of the second molar, potentially leading to its eventual loss.
The wisdom tooth’s position also creates an area that is nearly impossible to clean effectively, leading to the accumulation of plaque and bacteria against the back surface of the second molar. This contact point becomes highly vulnerable to decay, often resulting in large cavities on the distal surface of the second molar. These lesions are difficult to detect early and often require complex restoration, or even extraction of the second molar, to manage the decay caused by the neighboring tooth.
While wisdom teeth are often blamed for causing shifting or crowding of the front teeth, the scientific evidence supporting this widespread belief remains mixed. The most significant and well-documented structural harm caused by a retained third molar is the localized damage inflicted directly upon the adjacent second molar through decay and root resorption.
Pathological Changes in the Jawbone
While less common than infections, deeply impacted wisdom teeth carry the risk of leading to pathological changes within the jawbone. The most common of these is the formation of a dentigerous cyst. This occurs when the sac of tissue that surrounds the crown of the unerupted tooth fills with fluid.
Dentigerous cysts are the second most frequent type of cyst found in the jaw and are most commonly associated with impacted lower third molars. These fluid-filled lesions are frequently discovered incidentally during routine radiographic examinations. As the cyst expands, however, it can displace the surrounding teeth and begin to erode the surrounding bone structure.
The growth of a large cyst can significantly weaken the jawbone, increasing the risk of a fracture from minor trauma. This slow erosion requires intervention, as delayed diagnosis can lead to extensive surgical procedures to remove the lesion and repair the defect. Furthermore, in rare cases, the epithelial lining of the cyst can transform into a more aggressive, though usually benign, tumor like an ameloblastoma.
Monitoring Healthy, Fully Erupted Wisdom Teeth
Not all wisdom teeth pose a threat, and removal is not universally required. A retained wisdom tooth is considered safe and healthy if it meets several specific criteria. When these criteria are met, the third molars can contribute to chewing and help maintain the natural alignment of the dental arch.
Retaining wisdom teeth avoids the potential risks associated with any surgical procedure, such as nerve damage or dry socket. The decision to keep them is a viable option when they are fully integrated into the mouth without causing localized issues.
Criteria for Retention
A retained wisdom tooth is considered safe and healthy if it meets specific criteria:
- Be fully erupted through the gum line.
- Be correctly aligned with the opposing tooth for proper bite function.
- Be positioned where they can be effectively cleaned every day.
However, even when a wisdom tooth is currently healthy, it still requires monitoring. The potential for developing problems, such as new decay or periodontal pockets, increases with age. Regular dental examinations, including periodic radiographic imaging, remain necessary to monitor the tooth’s health, bone levels, and the status of the adjacent second molar for early signs of compromise.