The oral cavity contains a complex network of sensory nerves, primarily from the trigeminal system, which provides sensation to the face, mouth, and teeth. When a nerve is accidentally injured during a procedure, it can result in altered or unpleasant sensation. Although this complication is uncommon, it is a known risk associated with various invasive dental treatments. The most frequently affected nerves are the Inferior Alveolar Nerve (IAN) and the Lingual Nerve (LN), which supply sensation to the lower jaw, lip, chin, and tongue.
Mechanisms of Nerve Injury During Dental Procedures
Nerve injury arises from distinct mechanical or chemical processes that disrupt the nerve’s ability to transmit signals. One common cause is trauma from a local anesthetic injection, often targeting the Inferior Alveolar Nerve (IAN) for a mandibular nerve block. The needle may directly contact or lacerate the nerve sheath, or the injection process can cause damage via a small hemorrhage within the nerve bundle. Additionally, certain local anesthetic solutions, especially those with higher concentrations, may have a direct neurotoxic effect on the nerve fibers. This type of injury often affects the Lingual Nerve (LN) due to its close proximity to the IAN injection site.
Surgical procedures, especially the removal of impacted wisdom teeth, present another category of mechanical injury to the IAN and LN. During extraction, the nerve can be directly cut, crushed, or stretched as the tooth is manipulated and removed from the bone. Dental implant placement also carries a risk, where the drill used to prepare the bone or the implant itself may inadvertently contact or compress the IAN within the mandibular canal.
A third mechanism involves chemical or thermal irritation, frequently seen in endodontic treatments like root canals. If filling material is extruded beyond the root tip and contacts the IAN, the material’s chemical properties can irritate or damage the nerve. High heat generated by burs during aggressive drilling or bone shaving near the nerve can also cause thermal injury, leading to inflammation and subsequent nerve dysfunction.
Recognizing the Signs and Symptoms
When a nerve injury occurs, the resulting change in sensation can manifest in several ways. The most immediate sign is paresthesia, an abnormal but non-painful sensation described as tingling, prickling, or “pins and needles.” Patients may also experience anesthesia, which is a complete or near-complete loss of sensation in the area supplied by the nerve. These changes are typically noticed immediately after the local anesthetic wears off, though in rare cases, symptoms may develop hours or days later due to swelling or hematoma formation compressing the nerve.
Dysesthesia or hyperesthesia involves an unpleasant or painful abnormal sensation. This can include a constant burning, a sharp electric-shock-like pain, or pain triggered by something that should not be painful, known as allodynia. Dysesthesia often significantly impacts the patient’s daily life, interfering with speaking, eating, and general comfort.
The location of symptoms indicates which nerve has been affected. IAN injury results in altered sensation in the lower lip, the skin of the chin, and the gums on the affected side. If the Lingual Nerve (LN) is involved, symptoms are felt in the anterior two-thirds of the tongue and the floor of the mouth. LN injury is also frequently accompanied by an altered sense of taste, as a taste-carrying nerve branch runs alongside it.
Treatment Options and Recovery Outlook
Initial management for a suspected dental nerve injury is typically a period of observation and conservative treatment. Many nerve injuries are classified as a temporary conduction block, or neuropraxia, which often resolves spontaneously as the nerve sheath recovers. Dentists monitor the patient for the first two to four weeks, as minor injuries frequently improve on their own during this early phase. The goal during this time is to manage symptoms and prevent secondary complications.
If symptoms persist beyond the initial few weeks, medical intervention supports nerve recovery and manages pain. Pharmacologic treatments include corticosteroids to reduce inflammation and swelling around the nerve. Anticonvulsant medications and certain antidepressants are also commonly prescribed to help stabilize the nerve fibers and control the sharp, shooting, or burning pain associated with dysesthesia. Some clinicians recommend B-vitamin supplements to support nerve health.
Referral to a specialist, such as an Oral and Maxillofacial Surgeon or a neurosurgeon, becomes necessary if there is no measurable improvement after three to six months. Surgical exploration may be warranted to assess the nerve’s condition. The goal of surgery is either to decompress the nerve if it is trapped by scar tissue or to perform a nerve repair, sometimes involving a nerve graft, if the nerve was severed.
The prognosis for recovery is variable and depends on the severity of the injury. Milder injuries often show full recovery within a few weeks to a few months. More severe injuries can take six months or longer to heal, and while significant improvement is common, some patients may be left with a permanent alteration in sensation. Even with permanent changes, the severity of the symptoms often lessens over time as the body adapts and the nerve attempts to regenerate.