Wisdom teeth are the last set of teeth to develop, typically emerging between the ages of 17 and 25. Because the human jaw often lacks sufficient space, they frequently become “impacted,” meaning they are trapped beneath the gum line or jawbone. While the most common symptoms associated with this impaction are pain and swelling, a problematic wisdom tooth can cause altered sensation or numbness in the face. This symptom, known as paresthesia, is uncommon but indicates direct interference with a sensory nerve.
The Direct Cause: Nerve Compression from Impaction and Infection
The potential for facial numbness originates from the close anatomical relationship between the lower wisdom teeth and the Inferior Alveolar Nerve (IAN). This nerve travels through a channel within the lower jawbone, known as the mandibular canal, and provides sensation to the lower teeth, the lower lip, and the chin. When a lower third molar grows at an awkward angle, such as horizontally or deep within the jaw, the root structure can develop in close proximity to the IAN.
Severe impaction can cause the tooth to exert continuous mechanical pressure directly on the nerve, leading to altered sensation or tingling. This pressure can cause a neurosensory disturbance, which indicates nerve impingement. Imaging often shows the tooth root overlapping or indenting the mandibular canal, highlighting the physical stress on the nerve bundle. Mechanical compression is one of the two main reasons a wisdom tooth may cause numbness.
The second primary cause is related to infection and inflammation. When a partially erupted wisdom tooth develops a severe infection, known as pericoronitis, an abscess can form. This infection causes significant swelling in the surrounding tissues and bone. The swelling can create indirect pressure on the IAN or other nearby nerves. Relieving the infection and the resulting pressure often resolves the temporary numbness in these cases.
Accompanying Signs of Problematic Wisdom Teeth
Since numbness is not a frequent symptom, patients often experience other common signs that their third molars are causing problems. One typical indicator is localized pain or a dull ache in the back of the jaw. This discomfort may be intermittent or constant, especially if the tooth is actively trying to erupt or has become infected. The pain sometimes radiates upward to the ear or temple, which can be mistaken for a headache or earache.
Infection around a partially erupted tooth is common and presents with distinct symptoms. The gums surrounding the molar often become red, swollen, and tender, sometimes accompanied by bleeding. An infection can also lead to persistent bad breath or an unpleasant taste in the mouth due to trapped food debris and bacteria.
A further common symptom is difficulty opening the mouth fully (trismus). This stiffness occurs when inflammation or infection spreads to the muscles responsible for jaw movement. An impacted tooth may also push against the adjacent second molar, potentially leading to crowding or shifting of existing teeth. Recognizing these signs often prompts dental consultation before nerve symptoms develop.
Diagnosis and Resolution of Facial Numbness
When a patient reports numbness or tingling, the dental professional must determine the relationship between the wisdom tooth and the IAN. The initial diagnostic tool is usually a panoramic X-ray, which provides a two-dimensional view of the entire jaw and shows the position of the tooth and the nerve canal. However, two-dimensional imaging can sometimes misleadingly suggest contact between the structures.
If the X-ray indicates a high-risk relationship, a Cone Beam Computed Tomography (CBCT) scan is often necessary. The CBCT provides a detailed three-dimensional image, allowing the surgeon to accurately map the nerve’s path relative to the tooth roots. This imaging helps determine if the tooth is merely close to the nerve or actively compressing it, which dictates the treatment plan.
If the numbness is occurring before any procedure, the primary resolution is to eliminate the source of pressure. This involves treating any existing infection with antibiotics to reduce swelling, followed by the careful extraction of the problematic tooth. In high-risk cases where the tooth is intimately wrapped around the IAN, some surgeons may opt for a coronectomy, a procedure where only the crown is removed, and the roots are left in place to avoid nerve trauma.
Numbness can also occur as a separate risk after the extraction procedure. This post-operative numbness is due to surgical trauma, such as bruising or stretching of the IAN or the Lingual Nerve, which supplies the tongue. While temporary IAN injury occurs in a small percentage of removals, permanent deficits are rare, affecting less than one percent of patients. Most post-operative sensory changes resolve within weeks to months as the nerve heals, though recovery can take up to 24 months.