Inferior Alveolar Nerve Block

Inferior alveolar nerve block is a procedure of giving anesthesia to the mandibular region to block certain areas from experiencing pain in those areas, and this is usually helpful to perform surgical procedures in the oral cavity.
If the Inferior alveolar nerve is blocked with the anesthesia solution, then the whole nerve along with its subdivisions like Mental nerve, Incisive nerve, lingual and the long buccal nerve are blocked. So the areas which are supplied with these branches of the nerve do not experience any pain for certain amount of time.

Table of Contents:
Areas anesthetized
Anatomical landmarks to remember
Indications for anesthesia
Technique for the nerve block
Symptoms of anesthesia

The main areas that are anesthetized are -

1. Body of the mandible, and the inferior portion of the ramus of the mandible.
2. Mandibular teeth.
3. Mucous membrane and the underlying tissues that are anterior to the 1st molar tooth.

Anatomical landmarks that you have to remember -

1. Mucobuccal fold
2. Anterior border of the ramus of the mandible
3. External oblique ridge
4. Retromolar triangle
5. Internal oblique ridge
6. Pterygomandibular ligament
7. Buccal sucking pad
8. Pterygomandibular space

Indications for giving the anesthesia -
These are the instances when the anesthesia is to be given in the inferior alveolar nerve block. Some are -

1. Analgesia for operative dentistry on all the mandibular teeth. When any surgery is performed on the mandibular teeth and bone region, the nerve is blocked to induce analgesia(loss of pain).
2. Surgical procedures on mandibular teeth and its supporting structures anterior to the first molar when its supplemented by anesthesia for lingual nerve. Here along with the Inferior alveolar nerve, the lingual nerve to tongue is also anesthetized.
3. Surgical procedures on the mandibular teeth and supporting structures posterior to the second bicuspid when supplemented by an anesthesia for the lingual nerve and long buccal nerve.

The pathway of needle during insertion -
The needle passes through the mucosa, thin plate of buccinator muscle, loose connective tissue and a variable amount of fat.

Technique for inferior alveolar nerve block -

1. If the patient is in a dental chair, the head of the patient is to be kept in a position so that when the mouth is opened, the body of the mandible of the patient is parallel to the floor.
2. The height of the chair is adjusted such that the mouth of the patient comes of the level of elbow of the operator.
3. The operator stands on the right side of the patient and with the left index finger or thumb palpates the mucobuccal fold.
4. The finger is then moved on the anterior border of the ramus of the mandible.
5. When the finger or thumb contacts the ramus of the mandible, it is moved up and down until the greatest depth of the anterior border of the ramus is identified.
6. The area of the greatest depth is called the Coronoid notch and it is in a direct line with the mandibular sulcus. This places the height of the mandibular sulcus.
7. The palpating finger is moved lingually across the retromolar triangle and onto the internal oblique ridge.
8. The finger or thumb, still in the line with the coronoid notch and in contact with the internal oblique ridge, is moved to the buccal side taking it with the buccal sucking pad. This will give better exposure to the internal oblique ridge, the pterygomandibular raphe and the pterygomandibular depression.
9. When the intraoral landmarks are palpated with the thumb, the operator may place the index finger extra orally behind the ramus of the mandible, so that the mandible is held between the 2 fingers.
10. A syringe with 1 5/8 inch, 25-guage needle is taken and then inserted parallel to the occlusal plane of mandibular teeth from the opposite side at a level bisecting the finger or thumbnail penetrating the tissues of pterygotemporal depression and entering the pterygomandibular space.
11. During insertion of the needle, the patient is asked to keep the mouth wide open. Needle is penetrated into the tissues until gently compacting bone on the internal surface of the ramus of the mandible.
12. This should be in the area of mandibular sulcus which funnels into the mandibular foramen.
13. The needle is then withdrawn about 1 mm, and then 1 – 1.8 ml of the solution is deposited slowly(1.5 to 2 minutes)
14. The needle is now withdrawn slowly, and the remainder of the solution is injected in this area to anesthetize the lingual nerve.

Symptoms of Anesthesia -
1. Subjective symptoms – Tingling and numbness of lower lip and when the lingual nerve is affected, the tip of the tongue.
2. Objective symptoms – Instrumentation necessary to demonstrate absence of pain sensation.