Mandibular Nerve and Inferior Alveolar Block

Mandibular Nerve

• The mandibular nerve is a branch of the trigeminal nerve (CN V)
• It’s responsible for sensory innervation of the lower jaw and motor innervation of the muscles of mastication
• The mandibular nerve splits into two divisions: anterior and posterior
• The anterior division innervates the muscles of mastication (masseter, temporalis, lateral pterygoid) and the buccal nerve
• The posterior division innervates the auriculotemporal, lingual, and mylohyoid nerves, as well as the inferior alveolar nerve
• The inferior alveolar nerve provides sensory innervation to the mandibular teeth and the lower lip

Inferior Alveolar Nerve Block

• Also known as a mandibular block
• Anesthetizes the inferior alveolar, incisive, mental and commonly the lingual nerves
• Used for procedures on multiple mandibular teeth in one quadrant
• Can be used when buccal and/or lingual soft-tissue anesthesia is needed

Inferior Alveolar Nerve Block: Indications and Contraindications

• Indications:
  • Procedures on multiple mandibular teeth in one quadrant
  • When buccal soft-tissue anesthesia (anterior to the first molar) is necessary
  • When lingual soft-tissue anesthesia is necessary
• Contraindications:
  • Infection or acute inflammation in the area of injection
  • Patients who might bite either the lip or the tongue (e.g., very young children or physically or mentally handicapped adults)

Inferior Alveolar Nerve Block: Advantages and Disadvantages

• Advantages:
  • A single injection provides a wide area of anesthesia
• Disadvantages:
  • Wide area of anesthesia may not be necessary for localized procedures
  • Rate of inadequate anesthesia (15% to 20%)
  • Intraoral landmarks not consistently reliable
  • Positive aspiration (10% to 15%, highest of all intraoral injection techniques)
  • Lingual and lower lip anesthesia can be discomfiting and potentially dangerous for some patients
  • Partial anesthesia is possible due to bifid inferior alveolar nerve and bifid mandibular canals

Inferior Alveolar Nerve Block: Alternatives

• 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; success rate is variable)
• Gow-Gates mandibular nerve block
• Vazirani-Akinosi mandibular nerve block
• PDL injection (for pulpal anesthesia of any mandibular tooth)
• Intraosseous (IO) injection (for osseous and soft-tissue anesthesia of any mandibular region, especially molars)
• Intraseptal injection (for osseous and soft-tissue anesthesia of any mandibular region)

Inferior Alveolar Nerve Block: Technique

• Right Inferior Alveolar Nerve Block:
  • Operator Position: Right-handed administrator should sit at the 8 o’clock position
  • Patient Positioning: Supine or semisupine with the head positioned so that the mandibular body is parallel to the floor
  • Palpation:
    • Index finger or thumb palpates the mucobuccal fold
    • Move finger posteriorly until contact is made with the external oblique ridge on the anterior border of the ramus
    • Move finger up and down until the greatest depth of the anterior border of the ramus is identified (coronoid notch, which lies directly in line with the mandibular sulcus)
    • Move finger lingually across the retromolar triangle and onto the internal oblique ridge
    • With the finger still in line with the coronoid notch and in contact with the internal oblique ridge, move it to the buccal side (take the buccal sucking pad with it)
    • Place the index finger extraorally behind the ramus (literally holding the mandible between the thumb and index finger to assess the anteroposterior width)
  • Needle Insertion:
    • Insert a syringe with a 15/8-inch, 25-gauge needle parallel to the occlusal plane of the mandibular teeth
    • Insert from the opposite side of the mouth at a level bisecting the finger or thumbnail
    • Penetrate the tissues of the pterygotemporal depression and enter the pterygomandibular space
    • Ask the patient to keep their mouth wide open during insertion
    • Keep inserting until gentle bony contact is made on the internal surface of the ramus
    • Average depth of penetration is 20 to 25 mm
    • Once bone is contacted, withdraw the needle by 1 mm to prevent subperiosteal injection
    • Aspirate in two planes; deposit 1.5 mL of anesthetic over 60 seconds if negative
    • Reapirate after withdrawing half the syringe length; deposit 0.2 mL to anesthetize the lingual nerve if negative

Inferior Alveolar Nerve Block: Left Technique

• Operator Position: Right-handed administrator should sit at the 10 o’clock position
• Patient Position: Same as for the right IANB
• Palpation: Use the left index finger or thumb to palpate the landmarks (same as for the right IANB)

Inferior Alveolar Nerve Block: Signs and Symptoms

• Subjective:
  • Tingling or numbness of the lower lip indicates mental nerve anesthesia (may not indicate pulpal anesthesia)
  • Tingling or numbness of the tongue indicates lingual nerve anesthesia (may be present without inferior alveolar nerve anesthesia)
• Objective:
  • No response during two consecutive tests (2 minutes apart) with freezing spray or EPT (80/80 output) indicates successful pulpal anesthesia
  • No pain during dental therapy
  • No pain on palpation of the buccal gingiva anterior to the mental foramen with a blunt instrument

Inferior Alveolar Nerve Block: Safety Feature

• Needle contact with bone prevents over-insertion and its complications

Inferior Alveolar Nerve Block: Precautions

• Do not deposit local anesthetic if bone is not contacted (risk of facial nerve paralysis)
• Avoid pain during bone contact

Inferior Alveolar Nerve Block: Causes of Failure

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

Inferior Alveolar Nerve Block: Complications

• Hematoma (rare):
  • Swelling of tissues on the medial side of the mandibular ramus after anesthetic injection
  • Management: pressure and cold to the area for 3 to 5 minutes
• Trismus
  • Difficulty opening the mouth
  • Usually caused by muscle spasms in the masticatory muscles
  • Management: heat application, muscle relaxants, gentle range-of-motion exercises

This quiz covers the anatomy and function of the mandibular nerve, a key branch of the trigeminal nerve responsible for sensory and motor innervation in the jaw. Additionally, it explores the inferior alveolar nerve block, including its indications and contraindications in dental procedures. Test your understanding of these crucial concepts in dental anesthesia.