What does the posterior superior alveolar nerve innervate?

The posterior superior alveolar nerve (PSA) is a division of the trigeminal nerve (cranial nerve V). The trigeminal nerve is separated into three major branches – V1, V2, and V3. The V2 branch is known as the ‘maxillary’ branch of the trigeminal nerve, and is responsible for sensory information in the maxillary area. The posterior superior alveolar nerve is a portion of the maxillary V2 nerve.

The PSA nerve innervates general sensory information to the maxillary sinus, maxillary molars, as well as the maxillary gingiva and bone.

What does the PSA nerve block anesthetize?

Pulpally, the PSA nerve block will anesthetize all three maxillary teeth. This is important for operative procedures. However, the mesiobuccal cusp of the first maxillary molar will only be anesthetized 72% of the time, and should be supplemented with infiltration injections if needed.

The buccal soft tissues of the maxillary molars will also be anesthetized. If extraction of the maxillary molars is required, a palatal injection would be beneficial when lifting the soft tissues with the periosteal elevator.

What is the proper technique when injecting a PSA nerve block?

The injection should be placed posterior to the maxillary molars. The syringe should be placed at a 45 degree angle in both a vertical and horizontal direction (to the mesiodistal plane and buccolingual plane). The tip should be penetrating to a depth of 15-16mm (about the length of a periodontal probe).

(n.d.) Local Anesthesia Techniques. Dr. Caputo. A.T. Still Missouri School of Dentistry and Oral Health.

(2017). Cranial Nerves and Autonomics. Dr. Brzezinski. A.T. Still Missouri School of Dentistry and Oral Health.