INFERIOR ALVEOLAR NERVE BLOCK

D. Abdullah al nasser

introduction

*IANB: commonly(but inaccurately ) referred to as the

mandibular nerve block.*It is useful technique for quadrant dentistry.

•*A supplemental block (buccal nerve) is needed only if soft-tissue anesthesia in the buccal posterior region is necessary.

Nerves Anesthetized

1 .Inferior alveolar, a branch of the posterior division ofthe mandibular

2 .Incisive3 .Mental

4 .Lingual (commonly)

Areas Anesthetized1 .Mandibular teeth to the midline

2 .Body of the mandible, inferior portion of the ramus3 .Buccal mucoperiosteum, mucous membrane anterior

to the mandibular first molar (mental nerve)4 .Anterior two thirds of the tongue and floor of the oral

cavity (lingual nerve)5 .Lingual soft tissues and periosteum (lingual nerve)

Indications1 .Procedures on multiple mandibular teeth in one

quadrant2 .When buccal soft-tissue anesthesia (anterior to the

first molar) is necessary3 .When lingual soft-tissue anesthesia is necessary

Contraindications1 .Infection or acute inflammation in the area of

injection (rare)2 .Patients who might bite either the lip or the tongue;

for instance, a very young child or a physically ormentally handicapped adult or child

Technique

1 .A 25-gauge long needle is recommended for the adultpatient.

2 .Area of insertion: mucous membrane on the medialside of the mandibular ramus, at the intersection oftwo lines: one horizontal, representing the height ofinjection, and the other vertical, representing theanteroposterior plane of injection

3 .Target area: inferior alveolar nerve as it passes downward toward the mandibular foramen but before itenters into the foramen

Landmarks

a. Coronoid notch (greatest concavity on the anteriorborder of the ramus)

b. Pterygomandibular raphec. Occlusal plane

of the mandibular posterior teeth

Procedure

For a right IANB, a right-handed administratorshould sit at the 8 o’clock position facing thepatient

For a left IANB, a right-handed administratorshould sit at the 10 o’clock position facing in thesame direction as the patient

Procedure

Position the patient supine (recommended) orsemisupine. The mouth should be opened wide topermit greater visibility of and access to the injectionsite.

Procedure

There are three parameters that must be consideredduring the administration of the IANB :

1 )the height of the injection ,2 )the anteroposterior placement of the needle

(which helps to locate a precise needle entry point ,)and

3 )the depth of penetration (which determines the location of the inferior alveolar nerve).

(1 )HEIGHT OF INJECTIONPlace the index fingeror thumb of your left hand in the coronoid notch.

An imaginary line extends posteriorly from the finger tip in the coronoid notch to the deepest part of the pterygomandibular raphe (as it turns vertically upward toward the maxilla) determining the height of injection. This imaginary line should be parallel with the occlusal plane of the mandibular molar teeth

(1 )HEIGHT OF INJECTION

The needle insertion point lies three fourths of the anteroposterior distance from the coronoid notch back to the deepest part of the pterygomandibular raphe.

Notice the placement of the syringe barrel at the corner of the mouth, usually corresponding to

the premolars

(2 )ANTEROPOSTERIOR SITE OF INJECTION

(2 )ANTEROPOSTERIOR

Needle penetration occurs at the intersection oftwo points.

(a )Point 1 falls along the horizontal line from thecoronoid notch to the deepest part of thepterygomandibular raphe as it ascends verticallytoward the palate as just described.

(b )Point 2 is on a vertical line through point 1about three fourths of the distance from theanterior border of the ramus. This determinesthe anteroposterior site of the injection.

(3 )PENETRATION DEPTH

bone must be contacted.

The average depth of penetration to bony contactwill be 20 to 25 mm ,

approximately two thirds to three fourths the length of a long dental needle.

If… If bone is contacted too soon (less than half the length of a long dental needle), the needle tip is usually located too far anteriorly (laterally) on the ramus ,To correct:

(i )Withdraw t he needle slightly but donot remove it from the tissue.

(ii )Bring the syringe barrel around toward the front of the mouth, over the canine or lateral incisor on the contralateralside.

(iii )Redirect t he needle until a more appropriate . depth of insertion is obtained The needle tip is

now located posteriorly in the mandibular sulcus.

If..

A, The needle is located too far anteriorly (laterally) on the ramus .

B, To correct: Withdraw it slightly from the tissues (1) and bring the syringe barrel anteriorly toward the lateral incisor or canine (2); reinsert to proper depth.

If… If bone is not contacted, the needle tip is usuallylocated too far posterior (medial). To correct:

(i ) Withdraw it slightly ) i n tissue leaving ( approximately one fourth its length in tissue

and reposition the syringe barrel more posteriorly ( )o ver the mandibular molars.

(ii ) Continue the insertion until contact withbone )20 25 i s made at an appropriate depth to

(mm.

If…

A, Overinsertion with no contact of bone. The needle is usually posterior (medial) to the ramus .

B, To correct: Withdraw it slightly from the tissues (1) and reposition the syringe barrel over the premolars (2); reinsert.

Procedure

When bone is contacted, withdraw approximately 1 mm to prevent subperiosteal injection.

Aspirate. If negative, slowly deposit 1.5 ml of anesthetic over a minimum of 60 seconds.

Slowly withdraw the syringe, and when approximatelyhalf its length remains within tissues, reaspirate. If negative, deposit a portion of the remaining solution (0.1 ml) to anesthetize the lingual nerve.

After approximately 20 seconds, return the patientto the upright or semiupright position.

Wait 3 to 5 minutes before commencing the dentalprocedure.

Signs and Symptoms1 .Subjective: Tingling or numbness of the lower lip indicates

anesthesia of the mental nerve, a terminal branchof the inferior alveolar nerve. It is a good indication thatthe inferior alveolar nerve is anesthetized, although nota reliable indicator of the depth of anesthesia.

2 .Subjective: Tingling or numbness of the tongue indicatesanesthesia of the lingual nerve, a branch of theposterior division of V3. It usually accompanies IANBbut may be present without anesthesia of the inferioralveolar nerve.

3 .Objective: No pain is felt during dental therapy.

Precautions

1 .Do not deposit local anesthetic if bone is not contacted.The needle tip may be resting within theparotid gland near the facial nerve (cranial nerve VII),

and a transient paralysis of the facial nerve is producedif solution is deposited.

2 .Avoid pain by not contacting bone too forcefully.

reference

•HANDBOOK OF LOCAL ANESTHESIA, Ed. 5

•Thank you