Inferior Alveolar Nerve Block: Anatomical consideration and Technique

Inferior Alveolar Nerve Block (IANB) is a technique for dental anesthesia used to produce anesthesia of the mandibular teeth, gingival tissues of the mandible and the lower lip.


Nerves Anesthetized

• Inferior alveolar (CN V3 branch)
• Incisive
• Mental
• Lingual

Areas Anesthetized

1. Mandibular teeth to the midline
2. Body of the mandible, inferior portion of the ramus
3. Buccal mucoperiosteum, mucous membrane anterior to the mental foramen (mental nerve)
4. Anterior two thirds of the tongue and floor of the oral cavity (lingual nerve)
5. Lingual soft tissues and periosteum (lingual nerve)

Indications

1. Procedures on multiple mandibular teeth in one quadrant
2. When buccal soft tissue anesthesia (anterior to the mental foramen) is necessary
3. When lingual soft tissue anesthesia is necessary

Contraindications

1. Infection or acute inflammation in the area of injection (rare)
2. Patients who are more likely to bite their lip or tongue, for instance, a very young child or a physically or mentally handicapped adult or child

Advantages

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

Disadvantages

• Wide area of anesthesia (not indicated for localized procedures)
• Rate of inadequate anesthesia (31% to 81%)
• Intraoral landmarks not consistently reliable
• Positive aspiration (10% to 15%, highest of all intraoral injection techniques)
• Lingual and lower lip anesthesia, discomfiting to many patients and possibly dangerous (self-inflicted soft tissue trauma) for certain individuals
• Partial anesthesia possible where a bifid inferior alveolar nerve and bifid mandibular canals are present; cross-innervation in lower anterior region

Symptoms

1. Tingling or numbness of the lower lip (mental nerve)
2. Tingling or numbness of the tongue (lingual nerve)

Signs

1. Using an electrical pulp tester (EPT) and eliciting no response to maximal output (80/80) on two consecutive tests at least 2 minutes apart serves as a “guarantee” of successful pulpal anesthesia in nonpulpitic teeth. 
2. No pain is felt during dental therapy.

Precautions

1. Do not deposit local anesthetic if bone is not contacted. The needle tip may be resting within the parotid gland near the facial nerve (cranial nerve VII), and a transient blockade (paralysis) of the facial nerve may develop if local anesthetic solution is deposited.
2. Avoid pain by not contacting bone too forcefully.

Text from: Handbook of Local Anesthesia (Malamed)

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