Which nerve is NOT affected by the infraorbital nerve block?

The infraorbital nerve block is primarily used to anesthetize the areas innervated by the infraorbital nerve, which includes branches such as the anterior superior alveolar (ASA) and middle superior alveolar (MSA) nerves. These nerves are responsible for sensation in the anterior teeth, premolars, and associated soft tissues.

The posterior superior alveolar (PSA) nerve, however, is not impacted by the infraorbital nerve block. The PSA nerve typically provides sensation to the maxillary molars and also does not pass through the infraorbital foramen, which is where the infraorbital nerve block is administered. Thus, the correct answer identifies the PSA nerve as unaffected by the infraorbital nerve block, aligning with the anatomy of the maxillary nerve branches.

The infraorbital block does affect the ASA and MSA nerves, which is why they are not the correct answer. The IO, which is short for the infraorbital nerve itself, would also be included in the affected nerves as it is the target of the block. Hence, the understanding of maxillary nerve anatomy is crucial to identifying which nerves are affected by this specific block.