Various gauges and length
In the U.S. the most used diameters are 25, 27, 30 gauges. The higher the gauge number, the smaller the diameter. Close to ~45% of the market uses the 30 gauge. Since 25 gauge has the largest diameter, it’s very useful for preventing needle breakage.
Needle lengths are usually ultra-small, small, or long with the long needle being used for deeper penetrations. The last thing you want is to insert a short needle and have it break.
Bevel Design
The bevel is critical for cutting through. The patient’s comfort can be both increased by the design of the bevel as well as the sharpness. You do not want a dull needle with a poor design. If the needle is dull, you are forced to apply significantly more force. More force = less comfort.
Bore
The bore is the opening portion of the needle. The design of the bore controls the flow and pressure of the injection.
As you press on the depressor (to inject the fluid), the tissue, arteries, capillaries, etc attempt to push back that fluid. If the design of the bore is high quality it will give you better control against the back-flow. If the design is poor, you’re forced to push with significantly more pressure.
What Makes a Good Dental Needle?
Ultimately it’s about the comfort of your patient. Here is a guide for choosing:
What is the design of the needle? Multi-beveled / scapel-bevel will provide the most comfort
How large is the bore? The larger the bore, the less pressure that is felt during the injection of fluid
How sharp is the needle? This is a no-brainer, you want the needle to cut like butter
How many gauges is the needle? Although this is shown less relevant, it’s still assumed that the higher the gauge size, the more comfortable for patients
Sources
Dionne et al. Management of Pain and Anxiety in Dental Office, 2002
Farsakian: The significance of needle gauge in dental injection, Compendium 1991; 12:262–268
Kaufman: A survey of pain, pressure and discomfort induced by commonly … Anesth Prog 2005; 52:122–127
Viva Learning — The Dental Needle
Malamed S. 2013 Handbook of Local Anesthesia 6th ed; Elsevier.
