Inferior Alveolar Nerve Block
The inferior alveolar nerve block technique is the one with the highest percentage of failure (15%-20%), so we have to train well to do it.
Causes of failure:
1. Anatomical variation in the height of the mandibular foramen on the ramus.
2. Wrong anatomical determination.
3. Injection into area of infection.
4. Greater depth of soft tissue penetration required.
5. Intravascular injection.
Nerve anesthetized | Anesthetized area |
Inferior alveolar nerve & its subdivisions (Lingual nerve & nerve to buccinator) | Body of the mandible & inferior portion of the ramus - Mandibular teeth - Mucous membrane & underlying tissues (anterior to the molars) |
Symptoms of anesthesia: (How to test anesthesia??):
1. In the maxilla, we test the anesthesia only by instrument (objective).We use the probe in certain point & pierce the mucosa till it touches the bone. If anesthesia is given correctly, so no pain will be felt except for pressure..
2. In the mandible, they are 2 ways (subjective & objective)
a) Subjective symptoms: tingling & numbness of the lower lip, corner of the mouth & tip of the tongue à due to lingual nerve block. N.B: Numbness always ends @ the midline.
b) Objective symptoms: Instrumentation reveals absence of pain sensation.
c) FOR YOU: Tell the patient not to close her/his eyes cause eyes is the 1st part of the body that detect pain, also early signs of toxicity can be detected through eyes. Therefore, opening eyes is very important for communication with the patient without words & for detecting early responses.
Contraindication of inferior alveolar nerve block:
1. Infection or acute inflammation in area of injection.
2. Very young children, physically or mentally handicapped patients.
Advantages:
One injection provides wide area of anesthesia
Disadvantages:
1. Failure (15%-20%)
2. Wide area of anesthesia
3. Positive aspiration rate 10%- 15%
4. Intraoral landmarks not consistently reliable
5. Lingual & lower lip anesthesia discomforting to may patients & possibly dangerous in certain individuals.
Technique:
*Use long needle, aspiration is very important because inferior alveolar artery is very close..
FOR YOU: Never ever redirect the needle inside the tissue, otherwise fracture may happen.
1. The index finger @ the left hand (for right handed) is placed in the mucobuccal fold opposite to the bicuspid teeth or area.
2. Move the finger posteriorly until reaching the external oblique ridge, then the anterior border of the ramus & to the coronoid process. N.B: tell the patient to open his mouth as wide as he can, so you can insert the needle correctly to get the correct landmark..
3. Keep the finger in contact with the anterior border of the coronoid process & move the finger down until the greater depth on the anterior border of the ramus (coronoid notch) is reached.
4. The finger is kept in contact with coronoid notch, and then rotates the finger so that the finger nail is turned towards the sagittal plane.
5. At this point, slide the finger tip lingually & felt the internal oblique ridge, this area is called the retromolar triangle.
6. The point of the needle insertion lies @ about 0.5 cm in front of the middle of the tip of the left index finger nail, the needle is distal to ptrygopalatine raphe. The anesthetic syringe loaded with the carpule, mounted with long needle (42mm) held by the operator right hand in a pen grasp & parallel to the occlusal plane of the lower teeth & directed from the premolar area of the opposite sideà the needle is inserted to the previous point.
7. If the needle is in the correct position, it should touch bone @ about 20 -40mm (2/3 of the needle is inserted), inject about 1.5 cc of the anesthetic solution.
8. Withdraw the needle about 0.5 mm & inject 0.5 cc of the anesthetic solution to anesthetize the lingual nerve (1/3 needle is inserted). Long buccal nerve will be anesthetized (block) if extraction of the 6th, 7th& 8th or large flab is done in this area ( 0.01 cc for long buccal nerve infiltration)
Needle pathway during insertion:
- Mucosa, a thin plate of buccinator muscle, loose C.T & fat
- If the needle is inserted far more posteriorly à Trismus may occur.
- If the needle is very deep inserted or inserted from the same site à parotid gland may be hurt & facial nerve injury may occur (facial nerve palsy) but it's more severe when inserted from the same side.
Approximating structures when the needle is in position, the position of the needle should be:
- Superior
- Anterior to deep part of the parotid gland
- Medial to the inner surface of the ramus of the mandible
- Lateral to the lingual nerve & medial ptrygoid muscle & sphenomandibular ligaments.
Errors in the needle insertion in case of inferior alveolar nerve block:
1. If the needle puncture is too high & too far medially from the internal oblique ridge à the solution may be injected into the lateral ptrygoid muscle & this result in trismus
2. The solution may be injected into superior constrictor muscle of the pharynx causing profound numbness of the throat & patient will complain of feeling something in the throat.
3. The needle may penetrate on the ptrygoid venous plexus which cover the medial ptrygoid muscle , and this may result into hematoma in the ptrygomandibular space (so for this reason we nerve give it to hemophilic patient).
4. Puncture point along the internal oblique ridge but too high & the needle is advance d to deeply
5. Numbness of the ear will result from anesthesia of the articulotemporal nerve or the solution may be deposited in the insertion of lateral ptrygoid muscle with subsequent soreness & trismus & no effective anesthesia to the teeth.
6. The needle may be passed through the sigmoid notch , the solution is deposited in the masseter resulting in muscle edema , trismus & no effective anesthesia
7. The needle puncture may be high , but not advanced too deeply, the solution may be deposited into temporalus muscle & the patient will complain of trismus, soreness & failure of anesthesia
8. If the needle passed the insertion of temporalus muscle, the patient may have weak anesthesia
9. If the needle puncture is along the internal oblique ridge but too low , this is the most common error , & it results in failure of anesthesia
a) The solution may deposited to the insertion of medial ptrygoid & the patient will complain of pain & trismus
b) The solution may deposited into the parotid gland with the resultant parotitis
c) The solution may be deposited into the parotid gland near the facial nerve with resultant relaxation of all facial muscles
d) The solution may deposit into the parotid & facial vein with resultant toxicity, pallor, weakness, nausea, convulsion, are quickly manifested & patient skin become pall & his blood pressure & pulse are lowered.
