A 35-year-old patient requires extraction of the lower left first molar. The dentist plans to administer an inferior alveolar nerve block. The structure marked **A** in the diagram represents the nerve that must be anesthetized to achieve successful block of all ipsilateral mandibular teeth and lower lip sensation. Which of the following is the most appropriate clinical endpoint to confirm successful anesthesia of the structure marked **A**?

Explanation

## Why "Numbness of the lower lip on the ipsilateral side" is right The inferior alveolar nerve (structure **A**) enters the mandibular foramen and gives off the mental nerve as its terminal branch before exiting through the mental foramen. The mental nerve supplies sensory innervation to the lower lip and chin. When the inferior alveolar nerve block is successfully administered, anesthesia of structure **A** results in numbness of the ipsilateral lower lip, which is the clinical gold standard for confirming successful block. This is the most reliable and commonly used test in dental practice to verify that the nerve block has taken effect before proceeding with tooth extraction (Gray's Anatomy 42e, Ch 30). ## Why each distractor is wrong - **Loss of sensation over the buccal mucosa of the posterior mandible**: While the inferior alveolar nerve does supply the mandibular teeth, the buccal mucosa of the posterior mandible is supplied by the buccal nerve (a branch of the anterior division of the mandibular nerve), not the terminal branch of the inferior alveolar nerve. This would not be a reliable endpoint for confirming block of structure **A**. - **Inability to move the mandible laterally**: Mandibular movement is controlled by the muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid), which are innervated by the anterior division of the mandibular nerve. The inferior alveolar nerve is purely sensory and does not innervate these muscles, so its blockade would not affect mandibular movement. - **Absence of sensation over the hard palate**: The hard palate is supplied by the greater palatine nerve and nasopalatine nerve (branches of the maxillary division of the trigeminal nerve), not the inferior alveolar nerve. Blockade of structure **A** would have no effect on palatal sensation. **High-Yield:** Always confirm successful inferior alveolar nerve block by testing lower lip numbness—this verifies anesthesia of the mental nerve (terminal branch) and ensures the block is effective before tooth extraction. [cite:Gray's Anatomy 42e Ch 30]