The third molars, commonly referred to as wisdom teeth, are the last set of teeth to develop, typically emerging in the late teenage years or early twenties. Because they erupt after all other adult teeth have settled, they frequently encounter a lack of available space in the dental arch. This spatial constraint often causes them to become “impacted,” meaning they are partially or completely trapped beneath the gum line or angled incorrectly. Retaining a problematic wisdom tooth, whether impacted or simply positioned poorly, can lead to a cascade of oral health issues.
Localized Gum Infections and Pain
The most common issue resulting from a partially erupted wisdom tooth is pericoronitis, a localized gum infection. This occurs when the tooth is only partially visible, leaving a flap of gum tissue (an operculum) draped over the crown. This tissue flap creates a difficult-to-clean pocket where food debris, plaque, and bacteria easily become trapped.
The trapped bacteria multiply rapidly, leading to inflammation, swelling, and infection of the surrounding soft tissue. Symptoms of acute pericoronitis include severe pain, a foul taste due to pus discharge, and swelling that may extend into the face and throat. In serious cases, the swelling can cause difficulty opening the mouth (trismus), and the infection may spread to other areas of the head and neck.
Damage to Adjacent Teeth and Bone Structure
Retaining a problematic wisdom tooth can cause significant mechanical harm to the neighboring second molar. When a wisdom tooth grows at an angle, it can press directly against the root or crown of the second molar, leading to permanent damage. This pressure can cause external root resorption, where the root structure of the second molar is gradually dissolved. In severe instances, this degradation requires the removal of both the problematic wisdom tooth and the otherwise healthy second molar.
The tight, angled contact point between the two molars creates a plaque trap that is nearly impossible to clean. This inaccessible area becomes a breeding ground for decay-causing bacteria, frequently leading to a cavity (caries) on the back surface of the second molar. Treating decay here is challenging, often requiring extensive procedures like a root canal, crown, or even extraction of the second molar. The presence of an impacted wisdom tooth also increases the risk of periodontal disease (gum and bone loss) surrounding the second molar.
Development of Cysts and Tumors
The follicular sac—the tissue surrounding the crown of an unerupted tooth—can undergo pathological changes if the tooth is retained. This tissue can develop into a fluid-filled sac known as a dentigerous cyst. These cysts are non-cancerous but grow slowly, exerting pressure on and destroying the surrounding jawbone while shifting adjacent teeth. Dentigerous cysts are the most frequent type of non-inflammatory cyst associated with impacted wisdom teeth.
In rare cases, the epithelial lining of the cyst or the follicular tissue can transform into a more aggressive growth. The most recognized example is the ameloblastoma, a benign yet locally invasive tumor. Ameloblastomas require extensive surgical removal due to their tendency to destroy jawbone tissue and their high recurrence rate. These growths usually develop silently and are often only detected through routine dental X-rays.
Situations Where Retention Is Safe
Not all wisdom teeth require removal; a subset can be safely retained without causing harm. The primary condition for safe retention is that the tooth must be fully erupted and correctly aligned in the dental arch. It should be functional, meeting an opposing tooth, and its position must allow for easy, effective daily cleaning. Crucially, the surrounding soft tissue must be healthy, with no deep periodontal pockets or signs of recurring infection.
Even when a wisdom tooth meets these criteria, continued monitoring by a dental professional is necessary. Regular clinical examinations and periodic radiographic evaluations, such as panoramic X-rays, ensure the situation remains stable over time. This monitoring detects subtle changes, like early signs of decay on the adjacent molar or the beginning of bone loss, before they develop into serious complications.