The Anatomy of the Inferior Alveolar Nerve

The inferior alveolar nerve supplies feeling to your lower teeth. It’s a branch of the mandibular nerve, which itself branches off from the trigeminal nerve. It’s sometimes called the inferior dental nerve.

Anatomy

All of the nerves in your body exist as symmetrical pairs, one on the left side and one on the right. They’re referred to as a single nerve in most cases unless it’s necessary to distinguish one from the other such as if it’s been injured on one side.

Nerves are structured a lot like a tree, branching out as they go so they can connect to various structures around your body and provide sensory function (feeling) and motor function (movement).

Structure

The inferior alveolar nerve is part of a cranial nerve called the trigeminal nerve. You have 12 cranial nerves originating from your brain, and the trigeminal is the fifth. It originates from the brainstem, which is low in the back of your skull and attaches your brain to your spinal cord.

As the trigeminal nerve wraps around your head on its way to your face, it splits into three branches, the:

• Ophthalmic nerve
• Maxillary nerve
• Mandibular nerve

The mandibular nerve sends out both motor and sensory nerves that deal with chewing and sensation in parts of your head, face, and mouth.

One of these is the inferior alveolar nerve, which runs along the lower teeth. It provides both sensory and motor functions.

Location

The inferior alveolar nerve splits off from the mandibular nerve near your temple. It then runs down the side of your face past the ear and jaw (temporomandibular joint) and spreads out across the lower part of your face.

The inferior alveolar nerve gives rise to:

• Mylohyoid nerve, which innervates the mylohyoid and digastric muscles in the lower portion of your face
• Dental nerve, which innervates the lower molars and premolars
• Mental nerve, which innervates your lower lip and chin
• Incisive nerve, which innervates the lower canine and incisor teeth

Anatomical Variations

While nerves and other parts of our anatomy have a “typical” shape, location, and structure, they’re not identical in all of us. It’s important for doctors to understand known variations in anatomy for diagnostic purposes and, especially, for medical procedures such as surgery and local anesthesia.

In a known but rare variation of the inferior alveolar nerve, the nerve splits in two, with the second nerve running alongside the first. Where the nerve travels through the mandibular bone (jaw), two holes called foramen exist instead of the usual one.

Function

The inferior alveolar nerve is considered a mixed nerve, meaning that it provides both motor and sensory function.

Motor Function

Through its mylohyoid branch, the inferior alveolar nerve is essential for movement in your mouth and jaw.

The mylohyoid and digastric muscles form the roof of your mouth. The mylohyoid muscle plays an important role in swallowing and speech. The digastric muscles are involved in any complex movement of your jaw, which includes chewing, swallowing, speaking, and breathing.

Sensory Function

Through its dental branch, the inferior alveolar nerve provides sensation to your lower three molars and two premolars per side.

Through its mental branch, it provides sensation to your chin and your bottom lip.

Through its incisive branch, it provides sensation to your front teeth, the canine and two incisors per side.

Associated Conditions

Common causes of injury to the inferior alveolar nerve include:

• Wisdom tooth removal
• Lower-jaw implant placement
• Root canal involving nerves close the nerve’s course through the mandible
• Deep injections of dental anesthesia
• Some types of oral surgery

This nerve can also be damaged by traumatic injury to the jaw or diseases that affect nerves, such as multiple sclerosis. Additionally, damage to the mandibular or trigeminal nerves impact the function of the inferior alveolar nerve.

Symptoms of damage to the inferior alveolar nerve include pain, abnormal sensations, and/or numbness in the chin, lower lip, or around the lower teeth. Some people may drool or have trouble opening their mouths.

Symptoms can have a major impact on quality of life, as they may interfere with:

• Speaking
• Eating and drinking
• Shaving and applying makeup
• Brushing teeth
• Kissing

Studies show that these symptoms are usually permanent; however, surgical injury of the inferior alveolar nerve is rare, with between 1% and 5% having problems with it in the week after surgery and 0.9% or less (zero in some studies) still have problems six months later. The prognosis for spontaneous healing after six months is poor, and surgery to repair the damage is often not successful.

Nerve Blocks

When you get a filling or have other dental procedures performed, it’s common for the doctor to give you a nerve block via injection. An inferior alveolar nerve block is one of the most commonly performed dental procedures.

The result is numbness in the lower teeth, chin, and lower lip. In some cases, the tongue will lose sensation as well because the lingual nerve, which innervates the tongue, sits near the inferior alveolar.

When nerve blocks cause injury, it may affect both the inferior alveolar and the lingual, because of this close proximity.

However, the lingual nerve has a fairly good record of healing, unlike the inferior alveolar.

Rehabilitation

Treatment of inferior alveolar nerve damage often depends on the cause. It can include conservative treatment, or, if that’s unsuccessful, surgery.

If the damage is due to a dental implant, the implant may be removed or replaced by a smaller implant.

Conservative treatment is especially important since surgical outcomes tend to be poor. They may include:

• Anti-inflammatory medications, including non-steroidal anti-inflammatories (NSAIDs) and prednisone
• Pain medications, including Neurontin (gabapentin), Ultram (tramadol), and amitriptyline
• Nutritional supplements, including B vitamins and Ginkgo biloba

In one small study, conservative treatment lead to improved symptoms in only 16% of people, while 70% saw no significant change in their symptoms. Those who improved tended to be the ones who got early treatment.

If you have pain or abnormal sensations following a dental procedure, let your dentist know right away.