Where should the needle tip be positioned during injection?

• A. In the soft tissue only
• B. On the bone
• C. In the maxillary sinus
• D. In the pterygopalatine fossa

Answer: (B)

Positioning the needle tip on the bone is essential because it anchors the insertion and places the anesthetic as close as possible to the nerve fibers that supply the tooth. When the tip contacts the cortical bone near the tooth apex, the solution diffuses through the surrounding cancellous bone and periosteum to reach the nerve endings efficiently, giving a more reliable block while minimizing the risk of going too deep or into unintended spaces. Depositing while the needle is still against bone also helps prevent inadvertent injection into soft tissue where diffusion is slower and less predictable.

If the needle were in soft tissue only, the anesthetic would spread in an area farther from the nerve and diffusion would be less predictable, often requiring more solution or time. Intra-sinus placement would involve a space not intended for nerve anesthesia and could cause sinus-related complications without delivering effective tooth anesthesia. Placing the needle into the pterygopalatine fossa would target a much deeper, more distant space with significant risk of vascular or nerve injury and is not part of standard maxillary anesthesia.