July 30, 2012

Concerning innervation of the face

A dental surgeon carries out a block of the inferior alveolar nerve by infiltrating local anaesthetic at the mandibular foramen. Which clinical feature may result from this procedure?

a) Numbness of the lower lip on the injected side
b) Ineffective block for the incisor teeth
c) Numbness of the side of the tongue
d) Inability of the patient to clench his jaws
e) Transient weakness of the facial muscles on the injected side

The correct answer is A

The inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve (V), traverses the inferior alveolar, or dental, canal of the mandible to supply all the teeth of that hemimandible; all the teeth on that side are therefore anaesthetised.

The mental branch of the nerve emerges through the mental foramen to supply the lower lip, which becomes numb in a successfully performed block. The muscles of the tongue, of mastication and of facial expression are not affected.

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