Inferior alveolar nerve block

The inferior alveolar nerve block anaesthetises the inferior alveolar branches of the posterior division of the mandibular nerve, the incisive nerve, and the mental nerve. It is used for procedures on multiple teeth in one mandibular quadrant, when buccal soft tissue anaesthesia or lingual soft tissue anaesthesia is required. Contra-indications are when infection is present in the area of the injection and in patients that may bite or self-mutilate the tongue after anaesthesia.

An intra-oral approach may be used to locate the mandibular foramen on the lingual surface of the mandible at a point half way along an imaginary line drawn between the last molar tooth and the angular process of the mandible. In large patients the mandibular foramen can be palpated by placing a finger intra-orally and palpating the lingual surface of the mandible caudal to the last molar tooth. It is often possible to palpate the bundle sheath containing the nerve as it enters (or disappears) into the foramen. In smaller patients or when the foramen cannot be palpated, the position of the foramen can be determined at a point midway between the last molar and angular process. This is achieved by placing the veterinarian’s finger and thumb on the outside of the patient’s head and the thumb intra-orally. The thumb is placed on the last molar tooth intra-orally and the forefinger on the angular process extra-orally, the mandibular foramen can be estimated to be halfway between these points.

A 30 gauge short needle (cat) and long needle (dog) is recommended. The mouth should be opened wide and the lip should be pulled laterally and the tongue reflected to the opposite side of the mouth. The bevel of the needle is orientated towards the bone. Insert the needle through the mucosa caudal to the last molar tooth towards the angular process. Advance the needle slowly until bone is gently contacted. The needle is advanced along the bone towards the entrance of the foramen until the tip is at the halfway point. The general depth of penetration is 10mm in the cat, 15mm in a small dog and 20mm in a large dog. Before injecting make sure: depth of needle is adequate. Do not deposit local anaesthetic if bone is not contacted. Aspirate. Slowly deposit 0.1mls (cat) and up to 0.5 mls (dog) over 60 seconds. Maximum volume is 1 cartridge per 10 kg body weight total volume in all sites. Slowly withdraw the needle. Wait for the anaesthetic to work.

Diagram showing position of mandibular foramen in a dog

Diagram showing position of mandibular foramen in a dog (the red line represents the distance from the mandibular 3rd molar to the angular process, the circle is the mandibular foramen highlighted by the yellow arrow).

Desired direction of intra-oral mandibular block in a dog

Desired direction of intra-oral mandibular block in a dog.

Desired direction of intra-oral mandibular block in a dog2

Desired direction of intra-oral mandibular block in a dog.

Diagram showing position of mandibular foramen in a cat

Diagram showing position of mandibular foramen in a cat (the red line represents the distance from the mandibular 3rd molar to the angular process, the circle is the mandibular foramen highlighted by the yellow arrow).

Desired direction of intra-oral mandibular block in a cat

Desired direction of intra-oral mandibular block in a cat.