Background

Mandibular nerve block (MNB) includes blocking mental, mylohyoid, buccal, inferior alveolar, auriculotemporal, lingual, and mylohyoid nerves. This results in anesthetizing the following: 

1. Teeth of the same side mandible up to the midline. 
2. Anterior 2/3rds of the tongue. 
3. Mouth floor 
4. Lingual and buccal, soft and hard tissues on the side of block administration. 
5. Temporal region, skin in jaw area, and posterior part of the cheek. 

Indications

The nerves in mandibular area can be typically managed with targeted nerve blocks rather than a comprehensive nerve block. A complete nerve block is indicated in the following situations. 

1. When an IAN (inferior alveolar nerve) block fails or is impractical- Occasionally teeth might be innervated with an accessory nerve originating near the IAN, which may not be affected by a block in IAN. 
2. For surgical procedures involving the mandible, an MNB (mandibular nerve block) can be performed either as a standalone procedure or in conjunction with general anesthesia, particularly for various dental treatments involving the adjacent soft tissues and lower teeth.
   This procedure is highly successful at a rate of 95% to 98%, while the IAN block has success in 65% to 85% of cases. 

Contraindications

This procedure is contraindicated in the following: 

1. Mandible fracture, regional anatomy distortion, presence of tumor, or infection in pterygomandibular space specific to Vazirani-Akinosi block 
2. Hypersensitivity to local anesthetic 
3. Children, non-cooperative, and trismatic patients particular to Gow-Gates technique. 
4. Inflammation at the injection site. 

Outcomes

This is a highly effective technique for managing pain in the lower jaw and surrounding regions, though patient-specific factors and technical variations can influence the outcomes. 

Equipment

This includes the following: 

1. Mouth retractors 
2. Nonaspirating or aspirating sterile syringe 
3. 36mm long needle of 250gauge 
4. Applicators with cotton- tip to control bleeding 
5. Local anesthetics like mepivacaine(2-3%), lidocaine (1-2%) without or with epinephrine, or bupivacaine (0.5%). 

  For small dental procedures, a dose of 1 to 5 mL is typically sufficient. When larger volumes are used, it is important not to exceed the maximum allowable dose. Dosing should be reduced for elderly and pediatric populations, as well as those with liver, cardiac, or renal conditions. 

Standard monitoring equipment such as NIBP, ECG, and pulse oximetry must be available. Basic equipment and resuscitation drugs should also be readily accessible. 

Patient preparation and positioning

The patient is typically seated in a semi-reclining position in a dental chair. During the procedure, the blood pressure, oxygen levels and heart rate of patient are closely monitored. 

Technique

Approach considerations 

Mandibular nerve block can be performed by the following techniques: 

1. Coronoid approach 
2. Vazirani- Akinosi technique 
3. Gow-Gates technique 

The 2nd maxillary molar is situated in between the 1st and 3rd molars, making it the 7th tooth from the midline. That portion of the tooth which can be seen is called the crown, that portion covered by gum consists of the three roots. The line separating the roots from the crown is called the cervical line. 

Technical considerations

Coronoid approach 

The patient is supine with the mouth in the neutral position. Request the patient to open and close the mouth a few times for the identification of the coronoid notch on the side of the block to be performed. 

Immediately following the preparation of the skin, introduce the 22-gauge needle at the midpoint of the notch, advancing perpendicular to the base of the skull to about 1-2 inches in depth to the lateral pterygoid plate. The point of the needle is then slightly withdrawn and redirected posteriorly and inferiorly to pass beyond the lateral pterygoid plate. After correction, paresthesias in the mandibular region should be appreciated at a depth of about 1cm. Once aspiration confirms proper placement , 3-5mL of local anesthetic solution is injected gradually. 

Vazirani-Akinosi technique 

Though the Vazirani-Akinosi technique still has its advantages over the Gow-Gates technique, the latter is especially useful when the former is not possible in patients with restricted mouth opening. This technique of anesthesia is less traumatic and has a lower rate of complications when compared with the former. The only drawback is that it is less potent ad compared to Gow-Gates technique. A recent study found no difference between them regarding the effectiveness of pain relief. This is absolutely a technique contraindicated in a case of inflammation or infection in the region of the maxillary tuberosity or pterygomandibular area. The main advantages of this approach are reduced post procedural complications, less pain during injection and rapidity of onset. 

The patient should lie in the semisupine position or be seated in a dental chair with the mouth closed. The dentist stands on the side where the block is going to be performed. Landmarks include: 

1. Pterygomandibular raphe 
2. Gingival margin on the 2nd and 3rd maxillary molars. 

This procedure will infiltrate the pteryomandibular space, containing the IAN, mylohyoid, and lingual nerve. The cheek of the patient will be retracted, and the insertion of the needle over the mandibular ramus, parallel to the occlusal plane, will be done. Slightly bend the needle so that it doesnot enter the muscle belly. Before reaching the pterygomandibular space, the needle will be inserted through the bucinator muscle and mucous membrane. After negative aspiration, inject 1.8mL of LA very slowly over one minute. 

Gow-Gates technique 

This technique is indicated when an inferior alveolar nerve block may be inadequate, either due to accessory nerve supply or anatomic variations, in a dental procedure. This technique provides a true mandibular block of nerve trunk before it divides into its three main terminal branches and reduces the risk of intravascular injection. However, it may result in unwanted anesthesia of the temporal region and lower lip, and it has a longer time of onset. The patient must lie semisupine or in the dental chair, and the operator must stand at his side. Landmarks include: 

1. The intertragic notch 
2. Distolingual cusp of 2nd maxillary molar tooth 
3. Mouth corner 

This procedure involves introducing the needle at the mesiolongual cusp and medial to the mandibular ramus. The trajectory should be such that it finally reaches the neck of the mandibular condyle. The parallel positioning is done with respect to an imaginary line drawn from the intertragic notch to the mouth angle. Advance the needle 2.5cm until it hits the bony neck of the mandibular condyle. Withdraw the needle a little and check or negative aspiration. Administer slowly 1.8mL of local anesthesia during one minute. 

Complications

This is relatively a safe technique and complications are unusual. Risks may include: 

1. Blood vessel injury 
2. Swelling and hematoma 
3. Persistent numbness or tingling due to nerve injury 
4. Needle track infection 
5. Allergies to medication 
6. Collapse of CNS and cardiovascular system because of systemic toxicity of local anesthetics 
7. Response to systemic toxicity may include symptoms like: 
8. Weakness 
9. Numbness 
10. Anxiety 
11. Tremors 
12. Dizziness. 

References

 Fluoroscopically guided mandibular nerve block: a modified lateral approach – PubMed (nih.gov) 

References

 Fluoroscopically guided mandibular nerve block: a modified lateral approach – PubMed (nih.gov)