Inferior Alveolar Nerve Block

The inferior alveolar nerve block (IANB) is indicated when deep operative or surgical procedures are undertaken for mandibular primary and permanent teeth. While a supraperiosteal injection (infiltration) may provide adequate anesthesia for the primary incisors and molars it is not as effective for providing complete anesthesia for the mandibular permanent molars.

A major consideration for IANB in the pediatric patient is that the mandibular foramen is situated at a lower level (below the occlusal plane) than in an adult. Thus, the injection is made slightly lower and more posteriorly than in an adult (Figure 8).

Figure 8. Inferior alveolar nerve block

Figure 8. Inferior alveolar nerve block

The areas anesthetized are the:

• Mandibular teeth to the midline

• Body of the mandible, inferior portion of the ramus

• Buccal mucoperiosteum, mucous membrane anterior to the mandibular first molar

• Anterior two thirds of the tongue and the floor of the oral cavity (lingual nerve)

• Lingual soft tissues and periosteum (lingual nerve)

The indications for the IANB are:

• Procedures on multiple mandibular teeth in a quadrant

• When buccal soft tissue anesthesia anterior to the first molar is necessary

• When lingual soft tissue anesthesia is necessary

Contraindications are:

• Infection in the area of injection

• Patients who are likely to bite the lip or tongue (young children and the mentally handicapped)

Technique:

• Depending on the age and size of the patient a 25 or 27 gauge long or short needle may be used.

• Lay the thumb on the occlusal surface of the molars, with the tip of the thumb resting on the internal oblique ridge and the ball of the thumb resting on the retromolar fossa. Support the mandible during the injection by resting the ball of the middle finger on the posterior border of the mandible.

• The barrel of the syringe should be directed between the two primary molars on the opposite side of the arch.

• Inject a small amount of solution as the tissue is penetrated. Wait 5 seconds.

• Advance the needle 4mm while injecting minute amounts (up to a ¼ cartridge).

• Stop and aspirate.

• If aspiration is negative, advance the needle 4mm while injecting minute amounts (up to a ¼ cartridge).

• Stop and aspirate.

• If aspiration is negative, advance the needle while injecting minute amounts until bony resistance is met). Withdraw the needle 2mm.

• Stop and aspirate.

• The average depth of insertion is about 15mm (varies with the size of the mandible and the age of the patient). Deposit about 1 ml of solution around the inferior alveolar nerve.

• If bone is not contacted, the needle tip is located too posteriorly. Withdraw it until approximately ¼ length of needle is left in the tissue, reposition the syringe distally so it is over the area of the permanent molar and repeat as above.

• If bone is contacted too early (less than half the length of a long needle) the needle tip is located too anteriorly. Withdraw it until approximately ¼ length of needle is left in the tissue, reposition the syringe mesially over the area of the cuspid and repeat as above.

• The needle is withdrawn and recapped.

• Wait 3-5 minutes before commencing dental treatment.

The signs and symptoms of an inferior alveolar block are:

• Tingling and numbness of the lower lip (however it is not an indication of depth of anesthesia).

• Tingling and numbness of the tongue (see Lingual Nerve Block).

• No pain is felt during dental treatment.