A 7-year-old bit his lip while numb after a stainless steel crown placed under inferior alveolar nerve block. What could reduce the likelihood at the next appointment?

Use a shorter-acting anesthetic such as mepivacaine plain, or supplement with phentolamine to reverse soft-tissue numbness
Use bupivacaine for a longer-lasting block
Use articaine for the inferior alveolar block instead of lidocaine
Give the block earlier in the appointment

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Correct answer: A. Use a shorter-acting anesthetic such as mepivacaine plain, or supplement with phentolamine to reverse soft-tissue numbness

A. CORRECT. Prolonged SOFT-TISSUE anesthesia is what allows the self-inflicted lip and cheek trauma. Mepivacaine 3% PLAIN has a substantially shorter soft-tissue duration than lidocaine with epinephrine (roughly 2–3 hours versus 3–5). Phentolamine mesylate injected at the end of the procedure reverses the vasoconstriction and roughly halves the residual numbness. Parental education, cotton rolls, and reminder stickers are additional preventive measures.
B. Bupivacaine has the LONGEST soft-tissue duration of any dental local anesthetic (up to 12 hours) — it is specifically contraindicated in young children for exactly this reason.
C. Articaine's advantage is superior diffusion for INFILTRATION; for a block it offers no reduction in soft tissue duration, and 4% articaine carries a higher reported paresthesia rate for blocks.
D. Timing of the injection within the appointment does not change the total duration of soft tissue anesthesia.

Note: Always warn the parent explicitly: 'the lip will feel fat and strange for a few hours — watch him and do not let him chew or bite it.'

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