Which injection is associated with the highest risk of hematoma formation?

The posterior superior alveolar injection is associated with the highest risk of hematoma formation primarily due to its anatomical considerations. When administering this injection, the needle is inserted near the maxillary tuberosity, which is located near several vascular structures, including the maxillary artery and its branches. If the needle inadvertently pierces the blood vessel during the injection, it can lead to bleeding and hematoma formation in the surrounding tissue.

Furthermore, the posterior superior alveolar injection is often performed at a deeper location compared to other injections, increasing the likelihood of encountering vascular structures. Additionally, the density and thickness of the maxillary bone can sometimes obscure the needle's path, making it difficult to assess if a vessel has been contacted.

In contrast, other injections such as the inferior alveolar, maxillary anterior, and greater palatine injections involve different levels of vascular proximity or are situated in bones that have a lower risk of major blood vessel contact. This anatomical understanding clarifies why the posterior superior alveolar injection stands out as a procedure with a heightened risk of hematoma formation.