Inferior alveolar nerve anaesthesia

Inferior alveolar nerve block (abbreviated to IANB, and also termed inferior alveolar nerve anesthesia or inferior dental block) is a nerve block technique which induces anesthesia (numbness) in the areas of the mouth and face innervated by one of the inferior alveolar nerves 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.^[1] Although the long buccal nerve is not anesthetized by an IANB, meaning that an area of buccal gingiva (gums on the cheek side) of the lower back teeth retains normal sensation unless that nerve is blocked simultaneously. The inferior alveolar nerve is a branch of the mandibular nerve, the third division of the trigeminal nerve. This procedure attempts to anaesthetise the inferior alveolar nerve prior to it entering the mandibular foramen 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). This causes patients to lose sensation in:

their mandibular teeth on one side (via inferior alveolar nerve block)
their lower lip and chin on one side (via mental nerve 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 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.^[2]

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.^[2]
Gow-Gates technique - Invented by Australian 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.^[3] 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 maxillary mucogingival junction."^[4] 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.^[5]
A blood vessel may be punctured accidentally and a hematoma or "blood blister" may occur that will heal over time.^[5]
If needle is positioned too posteriorly, anasthetic may be put into parotid gland, 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 aected side for a few hours.^[2]
Also if the needle is placed too medially the medial pterygoid muscle can be injected, resulting in trismus.
The sphenomandibular ligament may act as a barrier to the agent if the injection is given too shallow and the lingual nerve is only anethetized.^[2]
This injection can rarely cause needle tract infections of the pterygomandibular space.^[6]^[7] 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 (disease causing).

References

↑ Agur, Anne M.R., and Arthur F. Dalley. Grant's Atlas Of Anatomy. 12th ed. Maryland, USA: Lippincott Williams & Wilkins, 2009. Print.
1 2 3 4 Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 216
↑ Gow-Gates technique, explained
↑ Meechan JG (January 1999). "How to overcome failed local anaesthesia". Br Dent J 186 (1): 15–20. doi:10.1038/sj.bdj.4800006. PMID 10028738.
1 2 Local Anesthesia for the Dental Hygienist, Logothetis, Elsevier, 2012
↑ Connor, JP; Edelson, JG (April 1988). "Needle tract infection. A case report.". Oral surgery, oral medicine, and oral pathology 65 (4): 401–3. doi:10.1016/0030-4220(88)90351-9. PMID 3163131.
↑ Hupp JR, Ellis E, Tucker MR (2008). Contemporary oral and maxillofacial surgery (5th ed.). St. Louis, Mo.: Mosby Elsevier. pp. 317–333. ISBN 9780323049030.

Anesthesia (outline)

Types	General Spinal Epidural Conduction anesthesia Local Topical Intercostal nerve block Sedation / Twilight anesthesia Dental (Inferior alveolar nerve) Neuroleptanalgesic anesthesia

Techniques	Airway management Anesthesia provision in the US Arterial catheter Bronchoscopy Capnography Dogliotti's principle Drug-induced amnesia Intraoperative neurophysiological monitoring Nerve block Penthrox inhaler Tracheal intubation

Scientific Principles	Blood–gas partition coefficient Concentration effect Fink effect Minimum alveolar concentration Second gas effect

Measurements	ASA physical status classification system Baricity Bispectral index Direct Fick method Entropy monitoring Fick principle Goldman index Guedel's classification Mallampati score Neuromuscular monitoring Thyromental distance

Instruments	Anaesthetic machine Anesthesia cart Boyle's machine Gas cylinder Laryngeal mask airway Laryngeal tube Medical monitor Odom's indicator Relative analgesia machine Vaporiser Double-lumen endotracheal tube Endobronchial blocker

Drugs	Benzodiazepine Etomidate General anaesthetic Inhalational anaesthetic Infiltration analgesia Ketamine Local anesthetic Methohexital Methoxyflurane Midazolam Neuraxial blockade Opiate Propofol Thiopental Thiopentone

Complications	Emergence delirium Allergic reactions Anesthesia awareness Local anesthetic toxicity Malignant hyperthermia Perioperative mortality Postanesthetic shivering Postoperative nausea and vomiting Postoperative residual curarization

Fields of study	Cardiothoracic Geriatric Oral sedation dentistry

Professions	Anesthesiologist Anesthesiologist assistant Nurse anesthetist Operating Department Practitioners Certified Anesthesia Technician Certified Anesthesia Technologist Anaesthetic technician

History	A.C.E. mixture Helsinki Declaration for Patient Safety in Anaesthesiology History of general anesthesia History of neuraxial anesthesia History of tracheal intubation

Organizations	American Association of Nurse Anesthetists American Society of Anesthesia Technologists & Technicians American Society of Anesthesiologists Anaesthesia Trauma and Critical Care Association of Anaesthetists of Great Britain and Ireland Association of Veterinary Anaesthetists Australian and New Zealand College of Anaesthetists Australian Society of Anaesthetists International Anesthesia Research Society

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