Final answer:
The correct injection to anesthetize the maxillary posterior teeth is the PSA (Posterior Superior Alveolar nerve block). It numbs the molars and sometimes the second premolar in the upper jaw and is specifically targeted for dental procedures in this area.
Step-by-step explanation:
The question relates to the field of dentistry and involves the understanding of dental anesthesia.
To anesthetize the maxillary posterior teeth, the correct injection is the PSA, which stands for Posterior Superior Alveolar nerve block. This nerve block numbs the molars (and sometimes the second premolar) in the upper jaw. For the maxillary anterior and premolar teeth, the Middle Superior Alveolar (MSA) nerve block may be used, although this nerve does not exist in all individuals. The Infraorbital nerve block is another option that can numb the maxillary anterior teeth and premolars. The GP refers to the Greater Palatine nerve block, which anesthetizes the hard palate and palatal soft tissues adjacent to the molars and premolars but does not numb the teeth themselves.
To summarize, the PSA injection is used to anesthetize the maxillary posterior teeth. This nerve block targets the area that serves the upper jaw molars and potentially the second premolar, thereby dulling any pain that might occur during dental procedures in this region.