15/06/2026
Inferior Alveolar Nerve Block (IANB)
Definition
The Inferior Alveolar Nerve Block is a mandibular nerve block in which local anesthetic is deposited near the inferior alveolar nerve before it enters the mandibular foramen, producing pulpal anesthesia of all mandibular teeth on that side.
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Anatomy
Target Area
The anesthetic is deposited in the pterygomandibular space near the mandibular foramen on the medial surface of the ramus.
Boundaries of Pterygomandibular Space
* Lateral: Ramus of mandible
* Medial: Medial pterygoid muscle
* Superior: Lateral pterygoid muscle
* Posterior: Parotid gland
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Landmarks
Intraoral
1. Coronoid notch (most important landmark)
2. Pterygomandibular raphe
3. Occlusal plane of mandibular teeth
Needle Insertion Point
* Lateral to the pterygomandibular raphe
* Approximately 6–10 mm above the mandibular occlusal plane
* Three-quarters of the distance from the coronoid notch to the deepest part of the raphe
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Technique
Right IANB
1. Operator stands at 8 o’clock position.
2. Retract cheek and identify landmarks.
3. Syringe barrel is positioned over the contralateral premolars.
4. Insert needle until bone is contacted at 20–25 mm.
5. Withdraw 1 mm.
6. Aspirate in two planes.
7. Deposit 1.5–1.8 mL anesthetic slowly.
8. Withdraw halfway and deposit 0.2–0.3 mL for lingual nerve anesthesia.
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Nerves Anesthetized
Inferior Alveolar Nerve
* All mandibular teeth on injected side
Mental Nerve
* Lower lip
* Chin
Incisive Nerve
* Anterior mandibular teeth
Lingual Nerve
* Lingual gingiva
* Floor of mouth
* Anterior two-thirds of tongue
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Areas Not Anesthetized
The buccal gingiva of mandibular molars is supplied by the Long Buccal Nerve, which requires a separate buccal nerve block.
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Signs of Successful Anesthesia
Subjective
* Tingling of tongue
* Numbness of lower lip
Objective
* No response to pulp testing
* Pain-free dental procedure
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Causes of Failure
Most Common Cause
Needle placed too low or too anterior to the mandibular foramen.
Other causes:
* Anatomical variation of mandibular foramen
* Cross innervation
* Accessory innervation via mylohyoid nerve
* Inadequate volume of anesthetic
* Acute infection
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Complications
Positive Aspiration
* Most common complication
* Incidence: 10–15%
Hematoma
* Injury to blood vessels
Trismus
* Trauma to medial pterygoid muscle
Facial Nerve Paralysis
* Occurs when anesthetic is deposited into the parotid gland
* Results in temporary inability to close eyelid
Needle Breakage
* Rare
* Avoid bending the needle
Paresthesia
* Persistent altered sensation after injection
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High-Yield FCPS Exam Points
🔹 Target: Inferior alveolar nerve before entry into mandibular foramen
🔹 Needle pe*******on depth: 20–25 mm
🔹 Most reliable sign of success: Lower lip numbness
🔹 Most common complication: Positive aspiration
🔹 Lingual nerve is anesthetized during withdrawal of the needle
🔹 Long buccal nerve block is needed for buccal soft tissue anesthesia of mandibular molars
🔹 Failure is most commonly due to incorrect needle position relative to the mandibular foramen