Which nerves are anesthetized by an anterior superior alveolar (ASA) nerve block?

• A. ASA, MSA, and IO
• B. IO and IA only
• C. ASA and GP
• D. MSA and IA only

Answer: (A)

The important idea is that the anterior superior alveolar (ASA) nerve is a branch that comes from the infraorbital nerve, which itself gives rise to several branches—the anterior superior alveolar, middle superior alveolar, and infraorbital/IO branches. When you perform an ASA block, the anesthetic is deposited in a spot where the infraorbital nerve and its branches are in close proximity. The solution can spread to the neighboring branches, anesthetizing not only the ASA area (the maxillary anterior teeth and their gingiva) but also the MSA distribution (which services some upper premolars and the MB root of the first molar) and the IO distribution (further facial tissues supplied by the infraorbital nerve). That’s why an ASA block can effectively numb the ASA, MSA, and IO territories.

If a choice implied only the ASA region or dragged in unrelated nerves like GP or IA, it wouldn’t capture the way the ASA block can affect the connected branches of the infraorbital nerve. The best answer recognizes that the block can extend to these three nerve distributions due to their shared pathway and proximity at the infraorbital foramen.