Mandibular Nerve Anatomy Quiz

Mandibular Nerve

• The mandibular nerve is a branch of the trigeminal nerve (CN V)
• It is responsible for innervating the muscles of mastication, the skin of the lower face and part of the temporal region, and the teeth of the lower jaw.
• The mandibular nerve splits into anterior and posterior divisions

Anterior Division

• Contains four branches:
  • Nerve to the lateral pterygoid muscle
  • Nerve to the masseter muscle
  • Nerve to the temporal muscle
  • Buccal nerve

Posterior Division

• Contains five branches:
  • Auriculotemporal nerve
  • Lingual nerve
  • Mylohyoid nerve
  • Inferior alveolar nerve
  • Incisive branch
  • Mental nerve

Inferior Alveolar Nerve Block

• Anesthetizes the inferior alveolar nerve, incisive nerve, mental nerve, and often the lingual nerve.

Indications

• Procedures on multiple mandibular teeth in one quadrant
• When buccal soft-tissue anesthesia is necessary (anterior to the first molar)
• When lingual soft-tissue anesthesia is necessary

Contraindications

• Active infection or inflammation in the area of injection
• Patients who might bite their lip or tongue

Advantages

• One injection provides a wide area of anesthesia

Disadvantages

• Does not provide localized anesthesia
• 15-20% chance of inadequate anesthesia
• Intraoral landmarks inconsistent
• 10-15% chance of positive aspiration
• Lingual and lower lip anesthesia can be uncomfortable or dangerous for some individuals
• Partial anesthesia possible due to bifid inferior alveolar nerve or bifid mandibular canals

Alternatives to Inferior Alveolar Nerve Block

• Mental nerve block for buccal soft tissue anesthesia anterior to the first molar
• Incisive nerve block for pulpal and buccal soft tissue anesthesia of teeth anterior to the mental foramen
• Supraperiosteal injection for pulpal anesthesia of central and lateral incisors, and sometimes premolars
• Gow-Gates mandibular nerve block
• Vazirani-Akinosi mandibular nerve block
• PDL injection for pulpal anesthesia of any mandibular tooth
• Intraosseous injection for osseous and soft-tissue anesthesia
• Intraseptal injection for osseous and soft-tissue anesthesia

Technique for Inferior Alveolar Nerve Block

• 25 gauge, long needle is recommended for an adult
• Area of insertion: mucous membrane on medial side of the mandibular ramus, at the intersection of two lines: one horizontal representing height of injection, the other vertical representing the anteroposterior plane of injection.

Landmarks for Inferior Alveolar Nerve Block

• Coronoid notch (greatest concavity on the anterior border of the ramus)
• Pterygomandibular raphe

Technique for Right Inferior Alveolar Nerve Block

• Dentist sits at 8 o'clock position facing patient
• Patient is supine or semisupine
• Palpate the mucobuccal fold with the left index finger or thumb, moving posteriorly until reaching the external oblique ridge.
• Move the finger up and down until identifying the greatest depth of the anterior border of the ramus (coronoid notch)
• Move the index finger lingually across the retromolar triangle and onto the internal oblique ridge
• Move the finger or thumb to the buccal side, taking the buccal sucking pad with it.
• Place the right index finger extraorally behind the ramus to assess anteroposterior width.
• Insert the needle parallel to the occlusal plane of the mandibular teeth, from the opposite side of the mouth, at a level bisecting the finger or thumb.
• Penetration should be towards pterygotemporal depression entering the pterygomandibular space
• Continue insertion until gentle contact with bone is made on the internal surface of the ramus of the mandible
• Average depth of penetration is 20-25mm
• Withdraw the needle approximately 1mm after bony contact to prevent subperiosteal injection
• Aspirate in two planes.
• If negative, slowly deposit 1.5mL of anesthetic over 60 seconds.
• Slowly withdraw the syringe and reaspirate when approximately half its length remains within the tissues.
• Deposit a portion of the remaining solution (0.2mL) to anesthetize the lingual nerve.

Technique for Left Inferior Alveolar Nerve Block

• Dentist sits at 10 o'clock position facing the patient
• Placement of the left arm around the patient's head allows for palpation with the left index finger or thumb.

Signs and Symptoms

• Subjective: Tingling or numbness of the lower lip indicates anesthesia of the mental nerve.
• Subjective: Tingling or numbness of the tongue indicates anesthesia of the lingual nerve.
• Objective: Lack of pain during dental therapy.
• Lack of pain when a blunt instrument is applied to the buccal gingiva anterior to the mental foramen.
• Use of a freezing spray or electric pulp tester (EPT) with no response to maximal output.

Safety feature

• The needle contacts bone to prevent overinsertion, but this is not a guarantee of pulpal anesthesia.

Precautions

• Do not deposit anesthetic if bony contact is not achieved.

Failures of Anesthesia

• Deposition of anesthetic too low (below the mandibular foramen)
• Deposition of anesthetic too far anteriorly (laterally) on the ramus
• Accessory innervation to the mandibular teeth

Complications

• Hematoma (rare):
  • Swelling of tissues on the medial side of the mandibular ramus after anesthetic deposition
• Management: pressure and cold (ice) to the area for 3-5 minutes
• Trismus:
  • Difficult opening of the mouth