Inferior alveolar nerve anaesthesia (also known as the inferior alveolar nerve block or IANB) is a technique for dental anaesthesia

Dental anesthesia

Forms of dental anesthesia are similar to general medical anesthesia except for the use of nitrous oxide, relatively uncommon outside of the dental field in the United States.-Local anesthetics:...

, used to cause numbness to the areas of the face innervated by the inferior alveolar nerve; namely, the lower lip and the teeth and gingivae of the mandible. This procedure attempts to anaesthetise the inferior alveolar nerve

Inferior alveolar nerve

The inferior alveolar nerve is a branch of the mandibular nerve, which is itself the third branch of the trigeminal nerve .-Path:...

 prior to it entering the mandibular foramen

Mandibular foramen

The Mandibular foramen is an opening on the internal surface of the ramus for divisions of the mandibular vessels and nerve to pass.-Contents:...

.

The inferior alveolar nerve is also known as the infra-alveolar nerve and the inferior dental nerve and is thus sometimes abbreviated as IAN or IDN. The inferior alveolar nerve is a branch of the mandibular nerve

Mandibular nerve

The mandibular nerve is the largest of the three branches of the trigeminal nerve.-Roots:It is made up of two roots:* a large sensory root proceeding from the inferior angle of the trigeminal ganglion....

, which is itself the third branch of the trigeminal nerve

Trigeminal nerve

The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...

.

Area of Numbness

Administration of anaesthesia near the mandibular foramen causes blockage of the inferior alveolar nerve and the nearby lingual nerve (supplying the tongue

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

). This is why the numbing of the lower jaw during dental procedures causes patients to lose sensation in:

• their teeth (inferior alveolar nerve block)
• their lower lip
  Lower lip
  The lower lip covers the anterior body of the mandible.It is lowered by the Depressor labii inferioris muscle....
  
   and chin (mental nerve
  Mental nerve
  Mental nerve is a general somatic afferent nerve which provides sensation to the anterior aspects of the chin and lower lip as well as the buccal gingivae of the mandibular anterior teeth and the premolars...
  
   block)
• and their tongue & gums except on the cheek side of the molars (lingual nerve
  Lingual nerve
  The lingual nerve is a branch of the mandibular nerve , itself a branch of the trigeminal nerve, which supplies sensory innervation to the tongue...
  
   block).

Administration of anaesthetic solution more superior to the mandibular foramen (usually in the vicinity of the ascending ramus of the mandible), will cause a more profound anaesthesia on that particular side of the mandible, also involving the buccal nerve

Buccal nerve

The buccal nerve is a nerve in the face. It is a branch of the mandibular nerve and transmits sensory information from skin over the buccal membrane and from the second and third molar teeth.-Course:It courses between the two heads of the lateral pterygoid muscle, underneath...

, which branches off of the mandibular nerve and supplies sensation to the buccal side of the mandible. This is often referred to as the V₃ block or the Gow-Gates block.

Injection techniques

There are a number of techniques that are commonly used to achieve inferior alveolar nerve anaesthesia. The most commonly used techniques involve an attempted block of an entire portion of the inferior alveolar nerve:

• Standard mandibular nerve block - The nerve is approached from the opposite side of the mouth by angling the syringe from the premolars on the opposite side. After piercing the mucosa and the buccinator muscle
  Buccinator muscle
  The buccinator is a thin quadrilateral muscle, occupying the interval between the maxilla and the mandible at the side of the face.-Action:Its purpose is to pull back the angle of the mouth and to flatten the cheek area, which aids in holding the cheek to the teeth during chewing.It aids whistling...
  
   between the palatoglossal & palatopharangeal folds until hitting bone (the ascending ramus), the syringe is drawn backwards slightly and brought parallel to the width of the ramus, so that the needle lies lateral to the medial pterygoid
  Medial pterygoid muscle
  The medial pterygoid , is a thick, quadrilateral muscle of mastication.The mandibular branch of the fifth cranial nerve, the trigeminal nerve, innervates the medial pterygoid muscle.-Origin and insertion:...
  
   at the mandibular foramen.
• Gow-Gates technique - Invented by Australia
  Australia
  Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
  
  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.
• Vazirani-Akinosi technique - a closed-mouth injection technique, the syringe is "advanced parallel to the maxillary occlusal plane at the level of the maxilla
  Maxilla
  The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
  
  ry mucogingival junction
  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...
  
  ."

With the advent of mandibular infiltration with articaine, commonly known in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 by the brand name Septocaine, certain dental and oral surgical procedures can now be performed without blocking an entire portion of the inferior alveolar nerve.

Dangers

If needle is positioned too posteriorly, anaesthetic may be put into parotid gland

Parotid gland

The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...

 (dangerous systemic effects), or paralyse Cranial Nerve VII (7), resulting in Bells Palsy-like symptoms.
Also if the needle is placed too medially the medial pterygoid muscle can be injected, resulting in trismus

Trismus

-Common causes:*Pericoronitis is the most common cause of trismus.*Inflammation of muscles of mastication. It is a frequent sequel to surgical removal of mandibular third molars . The condition is usually resolved on its own in 10–14 days, during which time eating and oral hygiene are compromised...

.

The sphenomandibular ligament is most often damaged in an inferior alveolar nerve block