Depending on how it is used, the needle design will influence whether the injection of painless or not. as well as the success or failure of the anesthesia itself. For every injecton, the dental professional’s first consideration is avoiding pain upon needle penetration. Standard dental anesthesia needles (triple bevel) penetrate into the tisues by streching and tearing them and thereby creating tensions that generate pain. The most recent generations of needle (double bevel) incise the tissues, like a scalpel. They liberate the tensions and can, therefore, be painless. However, these needles must be used correctly  the double bevel which renders a blade (fig.) enables the needle to penetrate deeper into the ligament to solve the problem of recurrent leakages with intraligamentary anesthesia. The double bevel, combined with the thicker lining of the needle, eliminates needle deflection, which is the main reason for the failure of ID nerve blocks.
For each anesthesia technique, a specific needle is available which reduces the pain and improves the results.
(7) Sixou J-L. Du bon usage du biseau lors de l’anesthésie. Info Dent. 2006 ; 88 : 2286-8
Comparaison aiguille standard et aiguille double biseau avec une extrémité plate et un bord tranchant