What needle should be used for infiltration?

• A. 30g long
• B. 27g short
• C. 25g short
• D. 32g short

Answer: (B)

For infiltration, the goal is to deposit the anesthetic into the soft tissue just under the mucosa, so you want a needle that stays shallow and minimizes depth while still delivering the solution smoothly. A short needle keeps the entry point within the mucosa and reduces the chance of going too deep or contacting bone, which lowers discomfort for the patient. The 27-gauge size provides a good balance between a thin enough bore to minimize tissue trauma and enough rigidity to control the injection, while allowing adequate flow of the anesthetic solution. A longer needle would risk deeper penetration, and a larger bore (like 25-gauge) could cause more tissue disruption for a shallow infiltration. A very fine 32-gauge would be more fragile and harder to control and may restrict flow, making the injection more difficult. Therefore, a 27-gauge short needle is the best choice for infiltration.