Injection pressure of anesthetics using 30-gauge needles with or without side perforation

A testing bench was designed and constructed to simulate resistance by living tissues to the injection of dental anesthetics. A full series of pressure measurements were made on that bench using 30-gauge dental needles: (a) without side perforation; (b) with side perforation; and (c) with side perforation, the axial perforation being clogged at the tip of the needle. The results obtained in this physical model suggest that (a) the injection pressure at the tip of the needles is essentially the same whether there exists a side perforation on the needle wall or not and (b) when the axial perforation is clogged, the anesthetic solution can flow into the tissues through the side perforation under approximately the same pressure as that measured with unclogged needles. The latter result may be of special interest for intraosseous and intraligamentary (periodontal ligament) injections.