Final answer:
The recommended injection depth for the PSA nerve block, used to anesthetize the molar teeth in the upper jaw, is approximately 16 mm.
Step-by-step explanation:
The precise injection depth for the PSA (posterior superior alveolar) nerve block can vary depending on the patient's individual anatomy. However, generally, the recommended injection depth is approximately 16 mm. The PSA nerve block is used to anesthetize the molar teeth in the upper jaw on one side of the mouth. The injection is performed in the mucobuccal fold above the second molar, angling the needle upwards towards the apex of the second molar at an appropriate depth to ensure successful anesthesia.