Mandibular Nerve and Block Anatomy Quiz

Mandibular Nerve

• The mandibular nerve is a major branch of the trigeminal nerve (cranial nerve V).
• It has two divisions: anterior and posterior.
• The anterior division supplies nerves to muscles: masseter, lateral pterygoid, and temporal muscles.
• The buccal nerve is part of the anterior division.
• The posterior division supplies the following nerves: auriculotemporal, lingual, mylohyoid, inferior alveolar, and mental nerves.

Inferior Alveolar Nerve Block

• Other name: Mandibular block

• Nerves anesthetized:

  • Inferior alveolar nerve
  • Incisive nerve
  • Mental nerve
  • Lingual nerve (commonly)

Inferior Alveolar Nerve Block: Indications

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

Inferior Alveolar Nerve Block: Contraindications

• Infection or acute inflammation in the injection area.
• Patients who might bite their lip or tongue (e.g., young children, or those with physical/mental disabilities).

Inferior Alveolar Nerve Block: Advantages

• One injection provides a wide area of anesthesia, useful for quadrant dentistry.

Inferior Alveolar Nerve Block: Disadvantages

• Wide area of anesthesia is not always necessary for localized procedures.
• Rate of inadequate anesthesia ranges from 15% to 20%.
• Intraoral landmarks may not consistently be reliable.
• Positive aspiration rate is 10% to 15%, the highest of all intraoral injection techniques.
• Lingual and lower lip anesthesia may be a concern, potentially dangerous for some patients.
• Partial anesthesia is possible with a bifid inferior alveolar nerve and bifid mandibular canals.

Inferior Alveolar Nerve Block: Alternatives

• Mental nerve block (for buccal soft tissue anterior to the first molar).
• Incisive nerve block (for pulpal and buccal tissues anterior to the mental foramen).
• Supraperiosteal injection (for pulpal anesthesia of central and lateral incisors and sometimes premolars, variable success).
• 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

• Needle: 25-gauge, long needle recommended for adults.
• Area of Insertion: Mucous membrane on the medial side of the mandibular ramus, at the intersection of horizontal and vertical lines.
• Target Area: Inferior alveolar nerve as it moves downward toward the mandibular foramen but before entering it.
• Landmarks: coronoid notch (greatest concavity on anterior border of the ramus), pterygomandibular raphe, occlusal plane of mandibular posterior teeth.
• Operator Position: Dentist sits at 8 o'clock position facing the patient (for right-handed operators). Patient is positioned supine or semi-supine; mandible is parallel to the floor when mouth is open.

Inferior Alveolar Nerve Block: Palpation of Intraoral Landmarks

• Left index finger or thumb is used to palpate the mucobuccal fold
• The finger or thumb is moved posteriorly until contacting the external oblique ridge on the anterior border of the mandibular ramus.
• The finger is moved up and down to identify the greatest depth (coronoid notch), this is in direct line with the mandibular sulcus.
• Palpating finger is moved lingually across the retromolar triangle and onto the internal oblique ridge.

Inferior Alveolar Nerve Block: Needle Insertion

• Syringe with 1 5/8 inch, 25-gauge needle.
• Needle inserted parallel to the occlusal plane of mandibular teeth, opposite side of the mouth.
• Level bisects the finger/thumb.
• Penetrates tissues of pterygotemporal depression and enters pterygomandibular space
• Patient keeps mouth open during insertion.
• Needle penetrates into tissues until contacting bone on internal surface of the mandibular ramus.
• Average depth of penetration to bony contact is 20–25 mm (approximately 2/3 to 3/4 the length of a long dental needle).

Inferior Alveolar Nerve Block: Aspiration and Anesthesia Deposition

• Aspirate in two planes before depositing anesthetic.
• Slowly deposit 1.5 mL of anesthetic over 60 seconds.
• Sequence of slow injection, reaspiration, slow injection, and reaspiration is recommended.
• Slowly withdraw syringe when about half the needle's length remains within tissues. Reaspirate.
• Deposit a portion of the remaining solution (0.2 mL) to anesthetize the lingual nerve. (Not always necessary).

Inferior Alveolar Nerve Block: Technique (Left Side)

• Right handed operator sits at 10 o'clock facing the patient.
• Left arm of the dentist is positioned around the patient's head to palpate landmarks with their left index finger/thumb.

Inferior Alveolar Nerve Block: Signs and Symptoms

• Subjective: Tingling or numbness of the lower lip (indicating mental nerve anesthesia).
• Subjective: Tingling or numbness of the tongue (indicates lingual nerve anesthesia).
• Objective: Use of a freezing spray (e.g., Endo-Ice) or electric pulp tester (EPT) – no response to maximal output (80/80) on two consecutive tests at least two minutes apart.
• Objective: No pain on the buccal gingiva anterior to the mental foramen during dental procedure.

Inferior Alveolar Nerve Block: Precautions

• Do not deposit anesthetic if bone is not contacted (needle may be resting in the parotid gland near the facial nerve).
• Avoid pain by not contacting bone too forcefully.

Inferior Alveolar Nerve Block: Failures

• Deposited anesthetic too low (below the mandibular foramen).
• Deposited anesthetic too far anteriorly (or laterally) on the ramus.
• Accessory innervation to the mandibular teeth.

Inferior Alveolar Nerve Block: Complications

• Hematoma: Swelling of tissues on the medial side of the mandibular ramus post injection. Management: apply pressure and cold (e.g., ice pack) for 3–5 minutes
• Trismus: Muscle soreness or limited movement when opening the mandible.
• Severe soreness is rare; slight soreness is common post IANB, typically resolved once anesthesia wears off.
• Transient Facial Paralysis: Deposition of anesthetic into parotid gland, resulting in an inability to close eyelid, and upper lip droop on affected side.

Test your knowledge on the anatomy of the mandibular nerve and the indications and contraindications for the inferior alveolar nerve block. This quiz covers essential aspects of dental anesthesia and its application in various procedures. Perfect for dental students and professionals looking to reinforce their understanding.