posterior superior alveolar (PSA) nerve block

what is the PSA nerve block?

anesthetizes the posterior superior alveolar nerve before it enters the mx (V2 injection)

used when multiple mx molars require treatment

other common names: tuberosity block, zygomatic block

what areas are anesthetized by the PSA nerve block?

pulps of: mx third molar, mx second molar, mx first molar (except for the MB root in some patients)

buccal bone and buccal periodontium over these teeth (NOT the palatal tissue)

why isn’t the MB root of the mx first molar always anesthetized with a PSA block

in approx 28% of patients, the MB root of the mx first premolar receives innervation from the MSA nerve, not PSA

when is a PSA nerve block indicated

when one or more mx molars require treatment

a supraperiosteal injection cannot be used due to inflammation or infection

a supraperiosteal injection has failed

when is a PSA nerve block contraindicated?

when the pt has a high risk of bleeding (hemophilia or other bleeding disorrders)

^ bc of greater risk of hematoma

alternative: supraperiosteal injection, PDL injection

advantages of the PSA nerve block

very little discomfort

high success rate (> 95%)

one injection anesthetizes multiple molars

uses less anesthetic than multiple infiltrations

disadvantages of the PSA nerve block

risk of hematoma

few bony landmarks during insertion

may require another injection for the MB root of the first molar

PSA technique

27-gauge short

insertion point: height of the mucobuccal fold above the mx second molar

target area: PSA nerve- posterior, superior, and medial to the posterior border of the mx

operator position for a PSA nerve block

for a right-handed clinician:

• left PSA- 10 o’clock

• right PSA- 8 o’clock

always prep the tissues at the mucobuccal fold before inserting the needle

most common complication of a PSA nerve block

hematoma caused by accidental puncture of the pterygoid venous plexus or the posterior superior alveolar artery

signs: rapid swelling, bruising, or discoloration

management: firm pressure, ice, reassurance

why does the PSA nerve block have a higher hematoma risk than many other injections

bc needle passes close to: pterygoid venous plexus and posterior superior alveolar artery

these vessels lie behind the mx tuberosity, making accidental puncture possible

what tissue does the PSA block not anesthetize

palatal soft tissue (if this is needed, administer a greater palatine block)