In dental school most of us learned to use the same two sizes and lengths of dental anesthetic needles. Once I got out into practice and started to experiment with different sizes and lengths, I changed my protocol.
I discovered through my years of practice that I like to use an extra short 30 gauge needle that is 12 mm long for maxillary anesthetic injections and for mandibular injections that are premolars and forward. What I like about the extra short needle is that it does not bend. For these two types of anesthetic injections, the extra short needle is long enough and easier to control than the “short” one we learned to use in dental school. As a bonus, if a patient asks to see the needle, I usually hear them say, “Oh, that’s not so bad.”
On a mandibular block, I prefer to use a 27 gauge needle that is 25 mm long. What I like about this size is that it gets me to the depth I need and is easy to manipulate. Rarely do I need a longer needle that is more difficult to control.