Inferior Alveolar Nerve Block

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Continuing Education Activity

The inferior alveolar nerve block involves the insertion of a needle near the mandibular foramen area intending to deposit a certain amount of local anesthetic solution near the entry of the nerve into the inferior alveolar canal. This activity describes the inferior alveolar nerve block and highlights the interprofessional team's role in improving care for patients who undergo inferior alveolar nerve block.


  • Identify the indications of the inferior alveolar nerve block.
  • Describe the main technique of inferior alveolar nerve block.
  • Review the alternative techniques for performing this procedure.
  • Outline the potential complications of the inferior alveolar nerve block.


The inferior alveolar nerve block is the most popular anesthetic techniques dentists use in their daily practice and involves the insertion of the needle in the mandibular foramen's surroundings to deposit local anesthetic solution near the entry of the nerve into the inferior alveolar canal.[1] 

One of this area's essential anatomical structures is the pterygoid plexus, which is located posterior and superior to the mandibular foramen area. Failure of this technique is mainly due to the operator's technical errors and not because of anatomical variation that may present in some rare cases. The most common reason is the operator's failure to identify anatomical landmarks used when performing the inferior alveolar nerve block. The failure rate is reported to be around 15% to 20%.[2]

Anatomy and Physiology

Branches of the Mandibular Nerve

The mandibular nerve is the third branch of the fifth cranial nerve, leaves the skull via the foramen ovale at the cranium base, and divides into anterior and posterior branches. The mandibular nerve's main trunk gives off a branch that supplies the medial pterygoid muscle and a meningeal branch known as nervous spinous. The anterior division is mainly motor in nature and gives off branches that supply the temporalis, lateral pterygoid, and masseter muscles. From the anterior division, a sensory branch known as a long buccal nerve emerges. The posterior division is mainly sensory, and it gives off the auriculotemporal, lingual, and inferior alveolar nerves. Before entering into the mandibular foramen, the inferior alveolar nerve gives a branch to the mylohyoid muscle and enters into the inferior alveolar canal, and terminates into two terminal branches, the incisive and mental nerves.[1]

Location of Mandibular Foramen

It is essential for an effective inferior alveolar nerve block that the local anesthetic solution is deposited in proximity to the nerve before its entrance into the foramen. Few studies have described that deposition of local anesthetic molecules into pterygomandibular space can produce the desired anesthesia.[3]

Literature suggests that the position of the mandibular foramen may vary. It may not always be located midway within the anteroposterior dimension of the mandibular ramus. It has been suggested that the foramen lies at a distance of around 2.75 mm from the mid of the mandibular ramus in the posterior direction. Also, the distance between the mandibular foramen and coronoid notch is suggested to be 19 mm, and it may be either at the level or below the occlusal plane. The location of mandibular foramen in relation to the occlusal plane may also vary with age. It is located below the occlusal plane level in adults, and in children, it is found below or at the level of the occlusal plane.[4]


The inferior alveolar nerve block provides temporary anesthesia to the mandibular teeth in the ipsilateral quadrant, gingival tissue, and mucoperiosteum of the mandibular arch and blocks the sensory innervations of the lower lip. Many surgical procedures of the mandible can benefit from this block, such as tooth extraction, surgical reconstruction, root canal, periodontal treatment, and stabilization in traumatic and fracture cases.[5]


A known allergy to a particular local anesthetic agent can contraindicate an inferior alveolar nerve block, but another agent can be applied in replacement. There is no absolute contraindication to the technique itself. Still, infection or acute inflammation at the injection site is known to decrease the efficacy of the anesthesia, and the procedure may be delayed until the acute phase of the disease has been resolved.[6] In patients who are likely to bite their lip or tongue due to anesthesia's prolonged effect, like in children or patients with developmental delay, special care is needed to prevent post-anesthesia traumatic lesions.


The most common anesthetic agent used for dental procedures is 2% lidocaine with 1:100.000 epinephrine. In patients where bleeding can be a problem, 1: 50,000 epinephrine is recommended for hemostasis. Articaine is frequently utilized in 4% concentration and with vasoconstrictors because of its vasodilatory effect. This agent has been reported to have a more prolonged effect than 2% lidocaine when used for the inferior alveolar nerve block.[7] A sterile, disposable long dental needle with a dental syringe is employed to deliver the anesthesia. Topical anesthesia, such as 20% benzocaine, may also be applied to the mucosa before the injection to provide numbness in the area and reduce pain.


The administration of the nerve block can usually be done as a sole operator by the person who is authorized to administer local anesthesia and have sufficient training in administering local anesthesia. In some cases, an assistant may be required to retract the cheek.


The anesthesia procedure must be explained to the patient and its potential risks and benefits and obtain informed consent. Also, before administering the nerve block, all the vitals must be checked, and a patch should be done so that the operator is equipped to manage the local anesthesia complications, including the essential instruments and medications. Thereafter, the patient should be seated or lying, and their head stabilized to prevent any sudden movements during the entire procedure. The patient should be asked to rinse their mouth with a mouthwash, and then the procedure of administering the block should be started.


Conventional Technique

The most common and oldest technique is the conventional inferior alveolar nerve block technique. To achieve successful anesthesia, the operator should recognize specific anatomic landmarks that guide the procedure. These landmarks include the coronoid process, coronoid notch, anterior and posterior margin of the mandible ramus, and the sigmoid notch. The most significant landmarks are the coronoid notch and the pterygomandibular raphe formed by buccinator and superior constrictor muscle. The preferred location for the entry of the needle is located between these two structures. The syringe barrel is placed over the premolars of the opposite side during the injection. An imaginary line starting from the deepest part of the pterygomandibular raphe and continued to the coronoid notch is the insertion point. The exact location of the needle's entry point is one-fourth the distance towards the raphe above the occlusal level of mandibular teeth. After locating the target area, the needle is inserted until bony resistant is felt. The depth of penetration is around 19 to 25 mm. After that, the needle is withdrawn gently and slowly. When the needle is inserted more than 25 mm, it may indicate that it is posterior towards the mandible's posterior border. If the bone is touched prematurely, it suggests an anterior position of the needle.[8]

Modifications in the Techniques

Various modifications or alternatives to the conventional technique of inferior alveolar nerve block have been reported.

  1. Thangavelu et al. proposed the internal oblique ridge as the only anatomical landmark. The thumb has to be placed on the retromolar area, and the tip of the thumb will indicate the internal oblique ridge. The insertion point will be 2 mm posterior to the internal oblique ridge and 6 to 8 mm above the thumb's midpoint. The syringe is located on the opposite premolars, and the needle is moved along until it touches the bone. This anesthesia technique has a success rate of 95%.[7]
  2. Boonsiriseth et al. employed a 30 mm long needle, and the insertion point was similar to the conventional inferior alveolar nerve block technique. However, the syringe barrel was located at the occlusal level of the ipsilateral teeth, whereas in the conventional method, it is located on the opposite side.[9]
  3. Suazo Galdames et al. advocated the inferior alveolar nerve block through the retromolar triangle approach. This technique involves the deposition of the anesthesia at the retromolar triangle. It is based on the fact that the bone is perforated by holes of different sizes in this area, allowing the passing of the buccal artery that anastomoses with the inferior alveolar vessels in the mandibular canal. The anesthesia then can reach the inferior alveolar nerve through the communication between the mandibular canal and the retromolar triangle. This technique has a success rate of 72%. It can be particularly valuable in patients with blood disorders where the conventional inferior alveolar nerve block may be difficult.[8]
  4. Other available techniques target mainly the mandibular nerve branches rather than only the inferior alveolar nerve. These include the Gow-Gate technique, Vazirani/Akinosi closed mouth technique, and Fischer three-stage technique.[10]

Computer-Controlled Local Anesthetic Delivery (CCLAD)

This automatic device can be used in some cases since it reduces the pain inflicted during the injection by continuously administering a small anesthetic solution at a slow rate.

There are single-use, disposable, and lightweight hand-piece devices. These are generally utilized for the attached gingiva, hard palate, and periodontal ligament anesthesia. These can also provide more accurate anesthesia delivery when a deep tissue block, like an inferior alveolar nerve block, is needed.[7]


Complications associated with the inferior alveolar nerve block vary from being common to rare. Facial paralysis has been reported, and the reason for this may be inadvertent deposition of local anesthesia in the parotid area region due to the advancement of the needle more towards the posterior border of the mandible. The mucosa tearing may cause pain and trismus during the progression or withdrawal of the needle.[11][12][13] 

Hematomas may develop due to the inadvertent nicking of the pterygoid venous plexus or following the intravascular injection of anesthetic solution. Paralysis of the lingual nerve, paresthesia, or dysesthesia has also been reported. Infrequent complications include ptosis, extraocular muscle paralysis, necrosis of the skin over the chin, diplopia, and abducens nerve palsy.[14]

Clinical Significance

The inferior alveolar nerve block, when correctly performed, provides excellent anesthesia of the ipsilateral mandibular teeth, gingiva, mucoperiosteum, and lower lip for a duration that allows performing the surgical procedures involved in daily dental practice. Providers must select the most suitable technique in each case and be knowledgeable of the anatomic landmarks and steps required. Even though many methods have been described, the conventional approach is the most still widely used.

Enhancing Healthcare Team Outcomes

The inferior alveolar nerve block is considered a challenging injection. The dentist and assistants and other healthcare team members must be aware and thorough with the knowledge of anatomy, necessary equipment, different anesthetic agents, and the technique itself to improve the outcome of any procedure.

Article Details

Article Author

Manu Rathee

Article Editor:

Melina Brizuela


10/6/2021 2:19:06 AM



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