Mental Nerve Block

Updated: Dec 05, 2014
  • Author: Marc S Orlewicz, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Overview

Overview

Lacerations of the lower lip and of facial soft tissue in the lower chin require proper anesthesia to ensure adequate cosmetic closure. The mental nerve block is a simple technique to supply anesthesia to this area. The mental nerve is a branch of the inferior alveolar nerve that exits via the mental foramen and divides into 3 branches below the depressor anguli oris muscle. One branch supplies the skin of the chin and the other 2 innervate the skin and mucous membrane of the lower lip. Note that this nerve block does not provide anesthesia to the teeth or mandibular soft tissue. The pain associated with the mental nerve block is significantly less than with other intraoral nerve blocks. [1, 2, 3, 4]

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Indications

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  • Lacerations of the lower lip
  • Lacerations to the soft tissue of the chin that extend from the lip anteriorly to the alveolar process (see side view below) and caudally to the mid body of the mandible (see front view below)
    Region of anesthesia (side view). Region of anesthesia (side view).
    Region of anesthesia (front view). Region of anesthesia (front view).
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Contraindications

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  • Noncooperative patient
  • Overlying cellulitis
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Anesthesia

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  • Some local anesthetic agents are typically used for dental procedures.
    • Lidocaine 1% (Xylocaine); rapid onset with duration of action lasting 30-60 min (longer duration if epinephrine added)
    • Mepivacaine 3% (Carbocaine); moderate onset with duration of action lasting 45-90 min
    • Bupivacaine 0.5% (Marcaine, Sensorcaine); slow onset with duration of action 2-4 h [5, 6]
  • Topical anesthetic agents are often useful prior to local anesthetic administration but are not required.
    • Viscous lidocaine (Xylocaine)
    • Tetracaine (Pontocaine)
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Equipment

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  • Local anesthetic agent of choice
  • 25-27 gauge needle
  • 5 mL syringe
  • Topical anesthetic (optional)
  • Gauze pads
  • Adequate light source
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Positioning

Place the patient in a semi-recumbent position, or in a dental/ENT chair, if available.

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Technique

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  • Apply topical anesthesia if desired.
  • Draw 2-5 mL of local anesthetic into the syringe. Agents may be combined (eg, lidocaine and bupivacaine) to achieve a longer duration of anesthesia
  • The intraoral approach to the mental nerve block with adjunctive topical anesthesia has been reported as subjectively and objectively less painful than the percutaneous approach. [7]
  • Locate the mental foramen.
    • Retract the cheek laterally.
    • The mental foramen is palpable between the 2 lower premolar teeth in adults and between the first and second primary molars in children.
    • The position of the mental foramen may differ among ethnic groups. [8]
  • Insert the needle along the lower gum line into the buccal fold between the premolar teeth (in adults) near the foramen (see image below). Do not place the needle directly into the foramen.
    Mental nerve block injection site. Mental nerve block injection site.
  • Aspirate.
  • Inject 2-3 mL of anesthetic.
    • Do not inject directly into the foramen.
    • Slow injection is significantly more comfortable than rapid injection (P < 0.001) [9]
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Pearls

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  • The mental nerve block provides anesthesia only to the lower lip and soft tissue of the chin.
  • If the foramen is not directly palpable, the anesthetic can be injected into the buccal mucosa between the 2 lower premolar teeth. Never inject into the foramen, as this can permanently damage the neurovascular bundle.
  • A dental aspirating syringe with a dental carpule can be used in place of a regular syringe. Slide the carpule into the syringe and place the needle on the end.
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Complications

See the list below:

  • Bleeding
  • Infection
  • Needle fracture
  • Intravascular injection
  • Neurapraxia (secondary to direct injection into the mental foramen)
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