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Inferior Alveolar Nerve Block

Overview

The inferior alveolar nerve block is the most common type of nerve block used for dental procedures. Knowledge of mouth and inferior alveolar nerve anatomy is required to perform the procedure.

See the image shown below.

Injection in proper area of ramus to effect alveol

Injection in proper area of ramus to effect alveolar nerve block

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The mandibular nerve exits at the base of the skull through the foramen ovale.

The first branch from the main trunk is the nervous spinosus, which runs superiorly through the foramen spinosum to supply the meninges.

The second branch is the first motor nerve, which supplies the medial pterygoid muscle. Inferior to that branch, the mandibular nerve splits into an anterior trunk (both sensory and motor) and a posterior trunk.

The motor component supplies the masseter, temporal, and lateral pterygoid muscles.

The posterior trunk radiates from the auriculotemporal nerve that gives sensory perception to the side of the head and scalp and sends twigs to the external auditory meatus, the tympanic membrane, and the temporomandibular joint. The posterior trunk then almost immediately divides into the lingual nerve and the inferior alveolar nerve.

The sensory trunk is the long buccal nerve that supplies the buccal soft tissue distal to the first molar.

The lingual nerve supplies the anterior two thirds of the tongue and the lingual surface of the mandibular gingiva.

The mandibular nerve sends a branch to the mylohyoid muscle and the anterior belly of the digastric muscle and then enters the mandibular canal. The mandibular nerve furnishes sensation to the following areas:

Mandible

Buccal gingiva anterior to the first molar

Lower lip and the pulps of all the mandibular teeth in that quadrant

The inferior alveolar nerve is the larger branch of the posterior division of the mandibular nerve. The inferior alveolar nerve enters the mandibular foramen in the ramus of the mandible (see the image below) to occupy the inferior alveolar canal in the body of the mandible.

Identifying mandibular ramus

Identifying mandibular ramus

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When the inferior alveolar nerve approaches the apex of the second bicuspid, it divides into two terminal branches, the mental and the incisive.

A nerve block of the intraoral mandibular or inferior alveolar nerve anesthetizes the following:

The body of the mandible and the lower portion of the ramus

All mandibular teeth

The floor of the mouth

The anterior two thirds of the tongue

Gingivae on the lingual surface of the mandible

Gingivae on the labial surface of the mandible

Mucosa and skin of the lower lip and chin

Understanding the underlying anatomy of the pterygomandibular space helps increase the effectiveness of inferior alveolar nerve blocks.

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