An impacted wisdom tooth is blocked from fully emerging, usually due to lack of space or obstruction from the adjacent second molar. Impaction can be partial, where the crown partially breaks through the gum line, or complete, where the tooth remains fully trapped beneath the gum and bone. Leaving an impacted tooth untreated can lead to complications affecting the tooth and surrounding oral structures.
Acute Infection and Inflammation
The most frequent immediate complication of a partially erupted wisdom tooth is pericoronitis, an acute infection involving the inflammation of the soft gum tissue covering the tooth crown. Bacteria and food debris become trapped in the small, difficult-to-clean space between the gum flap and the tooth surface, creating an environment for microbial growth.
Symptoms include pain, swelling, difficulty opening the mouth (trismus), and an unpleasant taste or bad breath (halitosis). While initial treatment involves antibiotics and professional cleaning, the infection is highly prone to recurrence if the partially erupted tooth is not addressed. The chronic cycle of inflammation will continue as long as the gum tissue remains in place to trap bacteria.
Structural Damage to Neighboring Teeth
Leaving an impacted third molar poses a long-term threat to the health of the adjacent second molar. The awkward angle makes cleaning the back surface of the second molar nearly impossible, leading to chronic plaque accumulation and decay (caries).
A more severe form of damage is external root resorption (ERR), where the root surface of the second molar begins to dissolve. This is caused by the constant pressure exerted by the impacted tooth as it attempts to erupt against the root. ERR is often asymptomatic and difficult to diagnose early, but it can severely compromise the second molar’s structural integrity, potentially leading to its premature loss. The risk of this resorption is particularly high when the wisdom tooth is angled forward (mesioangular impaction).
Risk of Cyst and Tumor Development
A serious, though less common, consequence of an untreated impacted wisdom tooth is the development of pathological lesions within the jawbone. The crown of the developing wisdom tooth is encased in a fluid-filled sac, and if the tooth remains impacted, this sac can accumulate fluid to form a dentigerous cyst. These cysts are typically slow-growing but can expand significantly over time.
As the cyst grows, it exerts pressure on the surrounding bone, leading to the destruction of the jaw structure and the displacement of nearby teeth. If these lesions are not detected and removed, the resulting bone loss can require extensive reconstructive surgery. The cellular lining of the dentigerous cyst can also undergo a transformation, leading to the development of benign, but locally aggressive, tumors such as an ameloblastoma.
Criteria for Active Observation
Not all impacted wisdom teeth require immediate removal; an alternative approach is active observation. This strategy is reserved for teeth that are fully bony impacted and have no connection to the oral environment. The tooth must be completely asymptomatic and show no signs of pathology, such as decay, root resorption, or cyst formation, on radiographic examination.
If a tooth meets these strict criteria, the patient must commit to a rigorous monitoring schedule. This typically involves a clinical examination every six to twelve months, coupled with a periodic panoramic X-ray every two years. The rationale is that a currently healthy tooth can unpredictably develop pathology over time. Active observation balances the risk of future surgery against the potential complications of delayed intervention.