Inferior Alveolar Nerve

The inferior alveolar nerve is a collection of nerve fibers which branch from the mandibular nerve present in the head. It provides sensation to and innervates the lower teeth. It also provides motor function via the mylohyoid nerve to the digastric’s anterior belly and the mylohyoid muscle.

Anesthesia which causes inferior alveolar nerve blockage is often administered to people undergoing dental treatments. Such patients may suffer from loss of sensation in their lower lip, teeth, and chin.

Structure of the inferior alveolar nerve

The inferior alveolar nerve is located near the mandible or the lower jaw. It passes into the upper side section of the mandible known as the mandibular foramen and offers an extension of nerve to the mylohyoid muscle present at the lower end of the oral cavity. The nerve also provides an added extension to the minor muscle called the digastric, located just under the mandible.

The inferior alveolar nerve is also situated inside the mandible. To be more precise, it is located within the mandibular canal. The entry of the nerve is facilitated by an opening present in the lower jawbone known as the mandibular foramen.

The row of teeth present in the bottom of the oral cavity gets sensory branches from the inferior alveolar nerve. These branches consist of the inferior dental plexus which is a network of bundled nerve fibers that provides sensory data to the teeth. The nerve also transmits sensation to incisors and canines.

On the anterior surface, the inferior alveolar nerve extends the mental nerve near the level of the second premolars on the mandible, later exiting the lower jaw through the mental foramen and thus providing sensory branches to the lower lip and the chin. The nerve then moves anteriorly and extends as the mandibular incisive nerve, thereby innervating the mandibular incisors and canines.

Inferior alveolar nerve block

• Causes: An IANB or inferior alveolar nerve block occurs due to anesthesia given during surgical or deep operative procedures that are performed for permanent and primary teeth located in the mandible. The anesthetic injection is given near the mandibular foramen, thereby causing blockage of the inferior alveolar nerve and the lingual nerve located nearby.
  • Infiltration or supraperiosteal injections may be sufficient to anesthetize the primary molars and incisors. It is however not so effective when it comes to providing full anesthesia for operative procedures on permanent molars of the mandible.
  • Doctors need to take one thing into consideration when performing mandibular dental surgeries and other procedures in children. The mandibular foramen in pediatric patients is located at a lower level, under the occlusal plane, as compared to an adult patient. Thus, for an inferior alveolar nerve block, doctors need to give the anesthetic injection more posteriorly and slightly lower in children than in adults.
• Symptoms: Numbing of the lower jaw associated with inferior alveolar nerve block can cause the following symptoms:
  • Loss of sensation in the chin and lower lip. Numbness and tingling in the lower lip.
  • Loss of sensation of the front 2/3^rd part of the tongue on the same side. Numbness and tingling of the tongue.
  • Loss of sensation on the teeth
  • Subsequent dental procedures/treatment do not cause pain.

Inferior alveolar nerve damage

• Symptoms: Patients with inferior alveolar nerve damage may suffer from pain, numbness, and changed sensations, and/or a combination of all the 3 symptoms. This can eventually lead to a substantial decrease in the overall quality of life of the affected person, psychological defects, and functional problems.
• Causes: Injury or damage of the inferior alveolar nerve often occurs at the time of dental surgical procedures such as placement of dental implant in the mandible, orthognathic surgery, wisdom tooth removal/surgery, local anesthetic deep dental injections, and root canal procedures which involves the occurrence of tooth roots right next to the nerve canal in the lower jaw.
  • Trauma and associated fractures of the mandible can also lead to damage of the inferior alveolar nerve.
  • Different causes come with different risk percentages which tend to vary in varied studies. The incidence of inferior alveolar nerve damage is also dependent on a variety of factors. For instance, removal of the 3^rd molars in teens comes with a lower incidence rate of nerve damage as compared to patients undergoing similar procedures but aged 25 years or older. The risk also increased many times over if the affected tooth is next to the dental canal of the inferior alveolar nerve. Risk associated with deep dental injections is minimal, while risk associated with mandibular dental implants is unknown, but patients need to be given information about possible inferior alveolar nerve damage.
• Treatment: Planned surgery, extensive assessment via cone beam CT scans, coronectomy procedures, use of infiltration dentistry, and careful extraction can help minimize inferior alveolar nerve damage.
  • Inferior alveolar nerve damage usually resolves on its own. Doctors may prescribe pain medications for managing inflammation and pain alleviation. If the condition persists, then a micro-neurosurgeon needs to be consulted.