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Local Anesthesia

Inferior Alveolar Nerve Block (IANB) — Simple OSCE & Viva Guide

A clear, high-yield guide to IANB landmarks, steps, and troubleshooting.

Quick Answers

What is an inferior alveolar nerve block?

Injection of local anesthetic near the mandibular foramen to anesthetize the inferior alveolar nerve before it enters the mandibular canal.

Which teeth are anesthetized?

All mandibular teeth on that side plus buccal soft tissues anterior to the mental foramen; lingual soft tissues via lingual nerve anesthesia.

Key landmarks?

Coronoid notch, pterygomandibular raphe, and mandibular occlusal plane. 2

Typical failure rate?

Commonly reported around 15–20% or higher, mostly from landmark/needle positioning issues or anatomic variation.

1. Why IANB is a “board exam favorite”

It is the standard block for mandibular restorative, surgical, and endodontic procedures, and is used globally in OSCE/viva stations.

  • High clinical relevance
  • Easy to assess in a station
  • Clear complications and troubleshooting points

2. Identify the landmarks (say them out loud)

Examiners want to hear your landmarks before you inject.

Landmarks

  • Coronoid notch: deepest concavity on anterior ramus
  • Pterygomandibular raphe: soft tissue fold between buccinator & superior constrictor
  • Occlusal plane: needle height reference (usually slightly above)

3. Step-by-step technique (classic OSCE order)

This is the sequence that scores best in stations:

IANB Steps

1. Patient open wide, mandible slightly to injected side
2. Palpate coronoid notch, visualize raphe
3. Insert needle lateral to raphe, ~6–10 mm above occlusal plane
4. Advance toward medial ramus until bone contact (~20–25 mm depth)
5. Withdraw 1 mm, aspirate, inject slowly
6. Withdraw halfway, deposit a small amount for lingual nerve
7. Wait 3–5 minutes, confirm anesthesia

Bone contact helps confirm correct depth and direction.

4. How to know it worked

  • Numb lower lip (mental nerve)
  • Loss of lingual sensation
  • No pain to EPT/cold on mandibular teeth

If lip isn’t numb after 5–7 minutes, the block likely missed.

5. Fast troubleshooting for failures

Most IANB failures are positional. Fix them like this:

  • No bone contact: needle too posterior; withdraw slightly and redirect medially.
  • Bone contact too early (shallow): needle too anterior; redirect posteriorly.
  • Partial anesthesia: supplement with buccal/lingual infiltration or intra-ligamentary.

Success varies with technique, solution, and inflammation (lower success in pulpitis).

6. Complications (high-yield viva list)

Be ready to list these calmly in any viva.

  • Hematoma (intravascular injury)
  • Transient facial nerve palsy (too posterior into parotid)
  • Trismus / muscle soreness
  • Needle breakage (rare)
  • Systemic toxicity if overdosed

Rare unusual complications exist but are not common OSCE targets.

7. OSCE model answer

What to say in a station

“I will perform an inferior alveolar nerve block to anesthetize mandibular teeth. My landmarks are the coronoid notch, pterygomandibular raphe, and occlusal plane. I insert the needle lateral to raphe slightly above occlusal plane, advance until bone contact, aspirate, and inject slowly. I then check lip numbness and tooth vitality after a few minutes.”

8. How DentAIstudy helps

DentAIstudy can generate:

  • Full OSCE scripts for injections
  • Viva one-page anesthesia summaries
  • Troubleshooting decision trees
  • MCQs on LA complications

Try Study Builder →

References

  • Rathee M, et al. “Inferior Alveolar Nerve Block.” StatPearls. 2023. 
  • Khalil H. “A basic review on inferior alveolar nerve block techniques.” J Dent Anesth Pain Med. 2014.
  • Nagendrababu V, et al. Local anesthetic solutions and IANB success in irreversible pulpitis. Int Endod J. 2019.
  • MSD Manual. “How to do an Inferior Alveolar Nerve Block.”
  • Aquilanti L, et al. Nerve-related adverse effects and failure rates of IANB. Int J Environ Res Public Health. 2022.