Dental needles

The most painful: nasopalatine block injection, followed closely by any of the palatal submucosal infiltration injections. i.e. the ones that you have in the roof of your mouth. Why? Because in this area the tissues are denser and accomodates very little in the way of volume.

The least painful: the maxillary buccal infiltration injection in the molar area. i.e. the ones you have in your cheek for upper back teeth. Why? Because there are few nociceptive nerve endings in this region of loose connective tissue.