Middle superior alveolar nerve block

The middle superior alveolar (MSA) nerve block anesthetizes the maxillary premolars with occasional overlap to the canine and first molar (see image below).

1. Landmarks: Locate the mucobuccal fold where it intersects with the junction of maxillary premolar 2 and molar 1.
2. Approach: While retracting the cheek, insert the needle into the intersection point at a 45-degree angle, and advance 1-1.5 cm.
3. Aspirate.
4. Slowly inject 2-3 mL of local anesthetic and massage for 10-20 seconds.