Final answer:
The MSA nerve block is performed at the b. mucobuccal fold above the maxillary second premolar to anesthetize the nerves serving the maxillary molars and surrounding periodontium.
Step-by-step explanation:
The landmarks for performing a Middle Superior Alveolar (MSA) nerve block are the b. mucobuccal fold above the maxillary second premolar.
The technique aims to anesthetize the pulp of the maxillary second premolar, first and second molars (excluding the mesiobuccal root of the first molar), and the buccal periodontium and bone overlying these teeth.
To perform an MSA block, the needle is inserted at a height above the mucobuccal fold above the maxillary second premolar, with the syringe aligned with the occlusal plane of the maxillary molars and the needle advanced superiorly and slightly posteriorly.
This location allows the local anesthetic to be deposited near the MSA nerve as it travels through the maxillary bone, causing temporary loss of sensation to the area supplied by the nerve.