An impacted tooth is one that has failed to fully erupt into its functional position due to a physical obstruction. This blockage can be caused by another tooth, dense bone, or excessive soft tissue preventing normal emergence. While any tooth can become impacted, the third molars, commonly known as wisdom teeth, are the most frequent example because they are the last to develop and often find insufficient space in the jaw.
The Visible Signs of Tooth Impaction
The most noticeable signs of an impacted tooth relate to the soft tissue surrounding it, especially when the tooth is only partially erupted through the gum line. A partially emerged tooth creates a flap of gum tissue, called an operculum, which traps food debris and bacteria. This leads to a localized infection and inflammation known as pericoronitis.
Patients may notice redness, tenderness, and significant swelling of the gum tissue immediately behind the last visible molar. This swelling can be accompanied by a bad taste or odor in the mouth, indicating the presence of pus and infection in the gum pocket. If the infection is severe, swelling can progress to the cheek or jaw area, causing difficulty opening the mouth fully (trismus).
Pain is a common symptom, often felt as a dull ache or persistent pressure in the back of the jaw. This discomfort may not be confined to the tooth itself but can radiate to other areas, presenting as an unexplained headache or earache.
Structural Types of Impaction
The physical appearance of an impacted tooth is governed by its structural orientation beneath the gums and bone. Impaction is classified based on the tissue covering the tooth and the angulation relative to the adjacent second molar.
Impaction is categorized by depth as either a soft tissue impaction, where the tooth is covered only by gum tissue, or a bony impaction, where the tooth is partially or fully encased in the jawbone. A soft tissue impaction is the most likely to show a small portion of the tooth’s crown visible in the mouth, whereas a fully bony impaction may show no visible sign of the tooth.
The angulation of the tooth is classified into four main types.
Angulation Types
The most common is a mesioangular impaction, where the tooth is tilted forward toward the adjacent molar. The opposite is a distoangular impaction, where the tooth is angled backward toward the jawbone.
A vertical impaction means the tooth is positioned straight up or down, parallel to the other teeth, but remains trapped below the gum line or bone. A horizontal impaction is where the tooth lies completely sideways, perpendicular to the adjacent tooth, which can lead to it pressing directly into the neighboring root.
Hidden Indicators and Diagnostic Confirmation
While visible symptoms can suggest an impacted tooth, a definitive diagnosis and treatment plan require detailed internal imaging. The physical appearance of the gums and jaw only provides a partial picture of the tooth’s location and its proximity to surrounding structures. The true nature of the impaction is revealed through a panoramic X-ray, also known as an orthopantomogram.
This two-dimensional image captures the entire jaw, allowing the dentist to confirm the tooth’s exact angle, its depth of impaction, and its relationship with the nerve canals. External root resorption is the destruction of the root surface of the adjacent second molar caused by the pressure from the impacted tooth. This damage often occurs without any outward symptoms until it is quite advanced.
Although the panoramic X-ray is the standard initial diagnostic tool, it may not accurately reveal the full extent of internal damage due to the overlapping of structures. Advanced imaging techniques, like Cone-Beam Computed Tomography (CBCT), are more precise in detecting early root resorption on the adjacent tooth.
Immediate Complications
If an impacted tooth is not addressed, the initial symptoms can quickly progress into more serious health complications. The persistent presence of the soft tissue flap over a partially erupted tooth creates an environment conducive to chronic infection. This infection, which starts as pericoronitis, can escalate into a localized abscess, characterized by the accumulation of pus, intense pain, and sometimes a fever.
The development of a dentigerous cyst is a serious consequence. This fluid-filled sac forms around the crown of the unerupted tooth. As this cyst grows, it exerts pressure on adjacent teeth and the jawbone, potentially leading to bone destruction and visible swelling. While the cyst is typically non-cancerous, its expansion can weaken the jaw structure over time.
The difficult-to-clean area created by a partially erupted tooth significantly increases the risk of tooth decay. Food and bacteria trapped beneath the gum flap can cause the impacted tooth itself to develop a cavity, or lead to decay on the distal surface of the neighboring second molar. This decay is difficult to treat and can compromise the health of an otherwise sound tooth.