Where should you inject to numb the middle superior alveolar nerve?

Injecting between the maxillary first and second premolars is the correct technique for numbing the middle superior alveolar nerve. This nerve supplies sensation to the maxillary premolars and sometimes the mesial buccal root of the first molar. By placing the injection in this specific location, the anesthetic can effectively diffuse to the nerve, blocking sensation and allowing for pain-free dental procedures on the areas it innervates.

The technique involves carefully palpating the area to locate the correct injection site and ensuring that the needle is directed towards the nerve. This precision is crucial for ensuring effective anesthesia and minimizing discomfort during dental work.

The other options would not effectively numb the middle superior alveolar nerve. Injecting above the apices of the tooth being worked on may not target the nerve accurately, as the nerve's pathway may not align with that location. Injecting in the lingual area of the molars focuses more on the lingual nerve rather than the middle superior alveolar nerve, and injecting in the midline of the upper lip does not target the appropriate nerve at all, making it ineffective for this purpose.