Why Inferior Alveolar Nerve Blocks Fail and How to Never Miss Again?

Even after following every step -identify the landmarks, angle the syringe just right, inject your LA, and the patient still jumps in pain when you start the prep. Is that correct?

You're not alone. Even when performed correctly, Inferior Alveolar Nerve Blocks (IANBs) fail in up to 15–20% of cases involving symptomatic mandibular molars1.

And for many clinicians, it feels like those failures come at the worst possible time: a hot tooth, an anxious patient, or a tight schedule.

Today, we break down the real reasons why IANBs fail and, more importantly, show you practical, evidence-backed strategies to get your patients numb the first time.

Why IANBs Go Wrong?

Anatomical Variation

Foramen position varies up to 10 mm vertically and horizontally, even between contralateral sides of the same patient 2.

Accessory innervation from the mylohyoid, auriculotemporal, or even transverse cervical nerves can bypass the conventional IANB zone.

Technique & Needle Placement

Too shallow, anterior/posterior, or incorrect angulation leads to missed deposition3.

Dense Cortical Bone

Thick mandibular cortex slows diffusion. Even a perfectly placed 1.8 mL may remain trapped in soft tissue.

Inflammation & Low pH

Inflamed pulps lower pH, shift lidocaine into ionized form and reduce nerve penetration.

7 Practical Solutions to Boost Your Block Success

Here are 7 easy and effective ways to combat IANB failures -

1. Switch to Gow-Gates or Akinosi Blocks

Gow-Gates Mandibular Nerve Block
Why it works?

Deposits anesthetic at the neck of the condyle, proximal to all V3 branches, ensuring more complete nerve trunk coverage.
 Key steps:

1. Have the patient open wide; identify the intertragic notch in the corner of the mouth line.
   

2. Insert a long needle just distal to the maxillary second molar cusp, aiming upward toward the tragus.
   

3. Advance until you contact bone (~25 mm), aspirate, then slowly inject 1.8 mL LA over 60 sec.

91–95% success shown in irreversible pulpitis cases, which outperforms the standard IANB4.

Akinosi-Vazirani Closed-Mouth Block
Why it works?

Accesses the pterygomandibular space without requiring mouth opening or bone contact, ideal for trismus or difficult landmarks5.
 Key steps:

• Keep mouth lightly closed; locate the mucogingival junction above the maxillary third molar area.
  

• Insert the needle parallel to the occlusal plane, advancing ~20 mm into the soft tissue between the ramus and tuberosity.
  

• Aspirate, then deposit 1.8 mL LA slowly.

• Clinical data show that the closed-mouth Akinosi–Vazirani block can achieve success rates up to ~96–97%, comparable or superior to both traditional IANB and Gow‑Gates, and is easier to perform in limited-opening situations6.

3. Supplement with Articaine Buccal Infiltration

• Articaine’s thiophene ring improves lipid solubility and bone penetration.

• This is especially valuable in cases with dense cortical bone, where infiltration enhances pulpal anaesthesia.

• A 1.7 mL buccal infiltration of 4% articaine after IANB boosts success from 57% to 94%, in mandibular molars7.

4. Buffer Your Lidocaine

• Add sodium bicarbonate (1 part 8.4% to 10 parts lidocaine with epinephrine) to reduce injection pain and accelerate onset by up to 1–2 minutes.

• Buffering may offer improvements in efficacy, particularly in inflamed tissue,  but the primary benefits are improved patient comfort and quicker anesthetic onset8.

5. Pre-Warm Your Cartridge

• Warming LA to 37 °C decreases patient discomfort and accelerates diffusion kinetics, often leading to a faster, more reliable nerve block onset.

6. Intraosseous or PDL Injection Rescue

• Intraosseous injection provides a significantly faster onset of anesthesia (1.8 minutes vs. 5.2 minutes) and a higher success rate (91.4% vs. 62.9%) than conventional IANB9.

• IOI is a highly effective primary or supplemental anesthetic technique in challenging cases requiring rapid and reliable anesthesia.

• Stabident and X-Tip intraosseous systems deliver local anesthetic directly into cancellous bone, with success rates over 90% in “hot tooth” cases where conventional blocks fail10.

• Periodontal ligament (PDL) injections, especially when administered with computer-controlled devices like The Wand, provide rapid, reliable supplemental anesthesia and serve as valuable adjuncts during challenging cases.

7. Confirm with Objective Testing

Dental practitioners can always run a quick test:

• Lip numbness ≠ pulpal anesthesia.

• Use cold testing or EPT to verify the block before drilling.

These quick, reliable tests ensure the block is effective and help prevent patient discomfort during procedures.

Final Takeaway

IANB failures are common but fixable.With the right techniques and tools, you can turn frustrating misses into consistent success.

References

1. Lee CR, Yang HJ. Alternative techniques for failure of conventional inferior alveolar nerve block. J Dent Anesth Pain Med. 2019;19(3):125–34.

2. Blanton PL, Jeske AH. The key to profound local anesthesia: neuroanatomy. J Am Dent Assoc. 2003;134(7):753–60.

3. Chakranarayan A, Mukherjee B. Arched needle technique for inferior alveolar mandibular nerve block. J Maxillofac Oral Surg. 2013 Mar;12(1):113–6.

4. Sarfaraz I, Pascoal S, Macedo JP, Salgado A, Rasheed D, Pereira J. Anesthetic efficacy of Gow-Gates versus inferior alveolar nerve block for irreversible pulpitis: a systematic quantitative review. J Dent Anesth Pain Med. 2021 Aug;21(4):269–282.

5. Malamed SF. Handbook of Local Anesthesia. 7th ed. St. Louis: Elsevier; 2019.

6. Ravi Kiran BS, Kashyap VM, Uppada UK, Tiwari P, Mishra A, Sachdeva A. Comparison of efficacy of Halstead, Vazirani–Akinosi and Gow Gates techniques for mandibular anesthesia. J Maxillofac Oral Surg. 2018 Dec;17(4):570–575.

7. Kanaa MD, Meechan JG, Corbett IP, Whitworth JM. Articaine buccal infiltration enhances the effectiveness of lidocaine inferior alveolar nerve block. J Endod. 2006 Oct;32(10):919–23.

8. Guo J, Yin K, Roges R, Enciso R. Efficacy of sodium bicarbonate buffered versus non-buffered lidocaine with epinephrine in inferior alveolar nerve block: A meta-analysis. J Dent Anesth Pain Med. 2018;18(3):129–142.

9. Kumar KC, Bhattarai BP, Subedi S. Comparison of intraosseous injection vs conventional IANB: meta-analysis. Oral Surg Oral Med Oral Pathol Oral Radiol. 2022;133(2):e33–e42.

10. American Association of Endodontists. Intraosseous anesthesia with the Stabident® and X‑Tip® systems. Endod Colleagues Excell [Internet]. 2009 Winter.