The third molars, commonly known as wisdom teeth, are the last set of adult teeth to erupt, typically appearing between the ages of 17 and 25. Because human jaws have evolved to be smaller, there is often insufficient room for these molars to emerge completely and align properly. When a wisdom tooth cannot fully erupt due to obstruction from other teeth, bone, or soft tissue, it is considered impacted. This impaction creates an environment that can lead to various dental problems if the tooth is retained. While some people keep their wisdom teeth without issue, complications usually arise when these teeth remain in a problematic, partially erupted, or fully impacted state.
Chronic Infection and Inflammation
One of the most frequent consequences of a partially erupted wisdom tooth is a localized infection known as pericoronitis. This condition involves the swelling and inflammation of the gum tissue surrounding the crown of the tooth, particularly the flap of gum tissue called the operculum. The space beneath this flap traps food debris and bacteria, which are nearly impossible to remove with standard brushing and flossing.
The acute phase of pericoronitis can cause severe symptoms, including intense pain that may radiate to the ear or throat, swelling of the gum and cheek, and difficulty opening the mouth fully (trismus). Pus discharge and a foul taste are common indicators that a localized infection has taken hold. If left untreated, the infection can spread into the deeper spaces of the neck and face, sometimes leading to life-threatening conditions like Ludwig’s angina, which requires immediate hospital intervention.
Structural Damage to Adjacent Molars
Retained, impacted wisdom teeth pose a direct physical threat to the health and integrity of the neighboring second molar. This damage manifests through two mechanisms: decay and root erosion. The tight, inaccessible contact point between an impacted wisdom tooth and the second molar creates a significant plaque trap that cannot be properly cleaned.
This environment fosters the rapid development of severe tooth decay (caries) on the distal surface of the second molar, often requiring extensive restoration or premature extraction. Additionally, when the wisdom tooth is growing at an angle, the physical pressure against the root of the second molar can trigger external root resorption. This process involves the erosion of the second molar’s root structure, compromising its stability and long-term viability. Impacted wisdom teeth in a horizontal or mesioangular position are significantly more likely to cause this destructive root damage.
Formation of Cysts or Tumors
A potentially destructive complication of retained impacted wisdom teeth is the formation of a dentigerous cyst, also known as a follicular cyst. This fluid-filled sac develops from the dental follicle, the tissue surrounding the crown of an unerupted tooth. Fluid accumulates between the crown and the epithelial lining, causing the cyst to slowly expand within the jawbone.
While these growths are benign, their continuous expansion can destroy surrounding bone tissue, displace adjacent teeth, and weaken the jaw structure. Dentigerous cysts are often painless and are only discovered incidentally during a routine dental X-ray, highlighting the silent nature of this pathology. Left untreated, these cysts necessitate complex surgical removal and bone grafting to repair the resulting defect. In rare instances, the cyst lining can transform into a more aggressive tumor, such as an ameloblastoma, which requires extensive surgery.
Criteria for Safe Retention and Monitoring
Not all wisdom teeth must be removed, and there are specific conditions under which safe retention is possible. A wisdom tooth can be kept if it is fully erupted into a functional position, allowing it to be easily cleaned and participate normally in chewing. Completely impacted teeth may also be retained if they are fully encased in healthy bone tissue, are asymptomatic, and show no radiographic evidence of pathology, such as cyst formation or damage to the second molar.
The decision to retain a wisdom tooth must be accompanied by a commitment to regular dental monitoring. Even if a tooth is currently asymptomatic, its position and condition can change over time. Dentists rely on periodic radiographic examinations, such as panoramic X-rays, to detect subtle changes like early bone loss, decay, or the initial stages of cyst development that are invisible to the naked eye. Without this ongoing professional assessment, a retained wisdom tooth may develop silent pathology that is only discovered when the damage has become extensive.