Inferior alveolar nerve block (abbreviated to IANB, and also termed inferior alveolar nerve anesthesia or inferior dental block) is a

nerve block Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block (sometimes referred to as simply "nerve block") is a short-term block, u ...

technique which induces anesthesia (numbness) in the areas of the mouth and face innervated by one of the

inferior alveolar nerve The inferior alveolar nerve (IAN) (also the inferior dental nerve) is a branch of the mandibular nerve, which is itself the third branch of the trigeminal nerve. The inferior alveolar nerves supply sensation to the lower teeth. Structure The in ...

s which are paired on the left and right side. These areas are the skin and mucous membranes of the lower lip, the skin of the chin, the lower teeth and the labial gingiva of the anterior teeth, all unilaterally to the midline of the side on which the block is administered. However, depending on technique, the long buccal nerve may not be anesthetized by an IANB and therefore an area of buccal gingiva adjacent to the lower posterior teeth will retain normal sensation unless that nerve is anesthetized separately, via a (long) buccal nerve block. The inferior alveolar nerve is a branch of the

mandibular nerve In neuroanatomy, the mandibular nerve (V) is the largest of the three divisions of the trigeminal nerve, the fifth cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve (ophthalmic nerve, maxillary nerve) which contain only aff ...

, the third division of the

trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewin ...

. This procedure attempts to anaesthetise the inferior alveolar nerve prior to it entering the

mandibular foramen The mandibular foramen is an opening on the internal surface of the ramus of the mandible. It allows for divisions of the mandibular nerve and blood vessels to pass through. Structure The mandibular foramen is an opening on the internal surfa ...

on the medial surface of the mandibular ramus.

Symptoms of anesthesia

Administration of anesthesia near the mandibular foramen causes blockage of the inferior alveolar nerve and the nearby lingual nerve by diffusion (includes supplying the

tongue The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...

). This causes patients to lose sensation in: * their mandibular teeth on one side (via inferior alveolar nerve block) * their

lower lip The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...

and chin on one side (via

mental nerve The mental nerve is a sensory nerve of the face. It is a branch of the posterior trunk of the inferior alveolar nerve, itself a branch of the mandibular nerve (CN V3), itself a branch of the trigeminal nerve (CN V). It provides sensation to the ...

block) * and parts of their tongue and lingual gingival tissue on one side except on the cheek side of the mandibular molars (via

lingual nerve The lingual nerve carries sensory innervation from the anterior two-thirds of the tongue. It contains fibres from both the mandibular division of the trigeminal nerve (CN V3 ) and from the facial nerve (CN VII). The fibres from the trigeminal nerve ...

block); a buccal block will anesthetize this later tissue area. Another symptom is harmless numbness and tingling of the body of the tongue and floor of the mouth, which indicates that the lingual nerve, a branch of the mandibular nerve, is anesthetized. Another symptom that can occur is “lingual shock” as the needle passes by the lingual nerve during administration. The patient may make an involuntary movement, varying from a slight opening of the eyes to jumping in the chair. This symptom is only momentary, and anesthesia will quickly occur.

Injection techniques

There are a number of techniques that are commonly used to achieve inferior alveolar nerve anesthesia. The most commonly used techniques involve an attempted block of an entire portion of the inferior alveolar nerve: * Inferior alveolar nerve block or IANB - The nerve is approached from the opposite side of the mouth over the contralateral premolars. After piercing the mandibular tissue on the medial border of the mandibular ramus within the pterygomandibular space and then contacting medial surface of the alveolar bone as well as being lateral to the pterygomandibular fold and the sphenomandibular ligament, the injection is given. * Gow-Gates technique - Invented by

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

n dentist George A.E. Gow-Gates in the mid-1970s, the needle is directed at the neck of the condyle just under the insertion of the lateral pterygoid muscle. This is used for more extensive anesthesia or when there is failure of the IANB * Vazirani-Akinosi technique - Invented by Sunder J. Vazirani in 1960 and later reintroduced in 1977 by Oyekunle J. Akinosi, a closed-mouth injection technique, the syringe is "advanced parallel to the maxillary occlusal plane at the level of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

mucogingival junction A mucogingival junction is an anatomical feature found on the intraoral mucosa. The mucosa of the cheeks and floor of the mouth are freely moveable and fragile, whereas the mucosa around the teeth and on the palate are firm and keratinized. Where ...

." This is used when the patient cannot open his mouth enough for the IANB.

Complications

* The most common adverse effect of this injection is accidental self-inflicted trauma after the procedure, either by biting the lip or tongue or by thermal burn caused by inadvertent drinking of fluid that is too hot. This classically occurs in children or those with learning disability.Local Anesthesia for the Dental Hygienist, Logothetis, Elsevier, 2012 * A blood vessel may be punctured accidentally and a hematoma or "blood blister" may occur that will heal over time. * If needle is positioned too posteriorly, anesthetic may be put into

parotid gland The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the man ...

, that may cause transient facial paralysis of the facial nerve or cranial Nerve VII (7). Symptoms of this temporary loss of the use of the muscles of facial expression include the inability to close the eyelid and the drooping of the labial commissure on the affected side for a few hours.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 216 * Also if the needle is placed too medially the medial pterygoid muscle can be injected, resulting in

trismus Trismus, commonly called ''lockjaw'' as associated with tetanus, is a condition of limited jaw mobility. It may be caused by spasm of the muscles of mastication or a variety of other causes. Temporary trismus occurs much more frequently than perma ...

. * The sphenomandibular ligament may act as a barrier to the agent if the injection is given too shallow and the lingual nerve is only anesthetized. * This injection can rarely cause

needle tract infection An injection (often and usually referred to as a "shot" in US English, a "jab" in UK English, or a "jag" in Scottish English and Scots) is the act of administering a liquid, especially a drug, into a person's body using a needle (usually a hyp ...

s of the

pterygomandibular space The pterygomandibular space is a fascial space of the head and neck (sometimes also termed fascial spaces or tissue spaces). It is a potential space in the head and is paired on each side. It is located between the lateral pterygoid muscle and ...

. This is because the mouth contains many types of bacteria which are normally harmless by virtue of the physical barrier that the mucosa presents. However, if they are inoculated into the tissues during an injection, they can become

pathogenic In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

(disease causing).

References

{{Anesthesia Anesthesia Dentistry