What is an Inferior Alveolar Nerve?

Inferior alveolar nerve: the largest branch of the inferior alveolar nerve. The inferior alveolar nerve descends along the medial side of the external pterygoid muscle, enters the mandibular canal through the mandibular foramen, and sends out many small branches in the canal, reaching the teeth and gums of the lower jaw; the final sacral foramen, called the phrenic nerve, is distributed in the palate and lower lip skin. Before the inferior alveolar nerve enters the mandibular foramen, it divides the mandibular hyoid nerve to the underside of the mandibular hyoid muscle, which dominates the mandibular hyoid muscle and the forelimb of the digastric muscle and is the motor branch. During mandibular surgery, the nerve can be anesthetized in the mandibular and sacral foramen.

Inferior alveolar nerve: the largest branch of the inferior alveolar nerve. The inferior alveolar nerve descends along the medial side of the external pterygoid muscle, enters the mandibular canal through the mandibular foramen, and sends out many small branches in the canal, reaching the teeth and gums of the lower jaw; the final sacral foramen, called the phrenic nerve, is distributed in the palate and lower lip. skin. Before the inferior alveolar nerve enters the mandibular foramen, it divides the mandibular hyoid nerve to the underside of the mandibular hyoid muscle, which dominates the mandibular hyoid muscle and the forelimb of the digastric muscle and is the motor branch. During mandibular surgery, the nerve can be anesthetized in the mandibular and sacral foramen.

Chinese name

Inferior alveolar nerve

Foreign name

Inferior alveolar nerve

Inferior alveolar anatomy:

Inferior alveolar nerve: It is a branch of the mandibular nerve. It is 1 cm behind the lingual nerve and enters the mandibular canal through the mandibular foramen. The inner branch of the mandible constitutes the lower dental plexus. The sensory fibers are distributed on the skin and mucous membranes of the mandibular teeth, gums, palate, and lower lip; the motor fibers are separated before entering the mandibular foramen, which are called the mandibular hyoid muscle nerves, which control the muscles of the same name and the forelimb of the digastric muscle.

Inferior alveolar nerve block anesthesia:

Indications: Surgery of the mandible, mandibular teeth and alveolar process.

Anesthesia method:

(1) Intraoral injection method:

1. Posture: sitting position, wide open mouth, lower tooth surface parallel to the ground.

2. Injection point: Use the mucosa 3 ~ 4mm outside the midpoint of the mandibular ligament as the puncture point.

3. Process: Place the syringe at the opposite bicuspid area at 45 ° to the midline of the face. The injection needle is 1 cm above the lower molar surface and parallel to it. It is inserted from the injection point, and then the needle is inserted about 2.5cm, directly to the medial bone surface of the ascending branch of the mandible. When no blood is drawn back, 2ml of medicine is injected.

(2) Oral injection:

1. Nerve groove projection position: from the anterior edge of the tragus to the intersection of the lower edge of the mandible and the anterior edge of the masticator muscle, the connection point is roughly the projection position of the inferior alveolar nerve groove above the inferior alveolar nerve hole That is the injection point of anesthetic.

2. Needle entry point: Along the lower edge of the lower jaw, take the midpoint of the line connecting the angle of the lower jaw to the front edge of the masticator muscle as the point of penetration.

3. Needle travel and depth: The line from the point of penetration to the point of injection is the path and depth of the needle.

4. Process: Put a sterile rubber sheet on the needle, and mark the length from the puncture point to the injection point. The needle is inserted from the puncture point, and it is close to the inside of the ascending branch of the mandible. When the skin piece reaches the skin of the lower edge of the mandible, it indicates that the needle point has reached the injection point, and 3 to 4 ml can be injected without blood to anaesthetize the alveolar nerve.

Anesthesia area: ipsilateral mandible, mandibular teeth, periodontal ligament, bicuspid to mid-incisor lip (cheek) gum, muco-periosteal, lower lip.

Anesthesia effect: The ipsilateral lower lip is swollen, numb, and painless response to probing.

Precautions:

After anesthetizing the alveolar nerve, the needle should be retracted about 1.0 cm, and then anesthetic is injected about 1.0 ml to anaesthetize the tongue nerve. When the needle is retracted to the mucosa, the needle is pushed slightly outward, and then a small amount of anesthetic is injected to anesthetize the buccal nerve. Anesthesia can also be achieved by injecting needles while injecting.

Inferior alveolar nerve related diseases:

1. Inferior alveolar nerve block:

Inferior alveolar nerve block is the trigeminal branch of the mandibular nerve. It is often used to repair mandibular teeth. Because the inferior alveolar nerve, arteries and veins enter the mandibular canal through the mandibular foramen, anesthetic is usually injected around the mandibular foramen on the inner side of the mandibular branch to block the inferior alveolar nerve. Blocking the inferior alveolar nerve can anaesthetize all the lower teeth on one side of the midline, the lower lip skin and mucous membranes of the inferior alveolar nerve palate, and the mucosa and gums of the lower alveolar lip and the skin of the jaw. Inserting the needle too far can pass through the parotid glands, causing transient paralysis of the facial nerve branches. The dentist often anesthetizes the alveolar nerve before repairing or removing the mandible. Because the phrenic nerve and incisor nerve are its terminal branches, the affected jaw and lower lip also lose sensation. The injection site of the anesthetic is located in the mandibular foramen, which is the opening of the mandibular canal. "Of all the routine injection procedures in dentistry, the lower alveolar nerve block is perhaps the most difficult to implement effectively" (Liebgott, 1986). If the needle tip travels too far back, it may enter the parotid glands, paralyzing the branches of the facial nerves, resulting in unilateral transient facial paralysis.

2. Inferior alveolar nerve injury:

Summary: Numbness caused by post-traumatic nerve injury usually has a history of injury or surgery. It is common in post-fracture nerve rupture or trauma, and after impacted tooth extraction.

Etiology: Nerve damage during tooth extraction When mandibular impacted third molar is removed, the root of the tooth is close to the inferior alveolar nerve because the tooth position is too low; or the operation is too rough, which can cause nerve damage.

Clinical manifestations: Nerve damage during tooth extraction The phrenic nerve may be damaged during extraction of mandibular bicuspids and molars. If the phrenic nerve is damaged only by flap or other operation, the nerve function can be removed within months. Recovery; if it is cut off at the palatine foramen, numbness or paresthesia of the lower lip and palatal area may occur, and recovery is not easy; buccal nerve may be damaged when the molars are removed, and buccal numbness may occur on the same side; Tooth extraction may damage the inferior alveolar, lingual, and buccal nerves, and numbness on the ipsilateral lower lip, cheek, or tongue half.

Key points for diagnosis:

More injuries, history of surgery or extraction history.

Paresthesia, pain, or numbness in the nerve distribution area.

Clinical examinations are hypoaesthesia and tactile loss or disappearance.

Treatment principles and plans:

(1) X-ray films should be taken before tooth extraction to understand the shape and position of the teeth and the relationship with the surrounding tissues. Pay particular attention to the positional relationship between the root and the inferior alveolar nerve. If the root of the tooth is close to or in communication with the mandibular canal, care must be taken during the operation to avoid scratching the alveolar socket. If the root of the tooth is accidentally pushed into the mandibular canal, do not forcefully remove it. Follow-up observation is possible.

(2) Treatment should be actively treated early. If there are opportunities and conditions for nerve reconnection, nerve anastomosis should be implemented as soon as possible. If conditions are not available, acupuncture, physical therapy, or hormones, vitamin B1, vitamin B12, etc. can be used to promote nerves. Recovery of functionality.