Adrenaline Dilution in Dental Local Anesthetic Cartridges: A Practical Method Using the Inner Needle of Intravenous Catheter

Local anesthesia is a routine medical procedure for dentists. To achieve the desired anesthetic effect of lidocaine and favorable hemostatic effects by adrenaline, the combination of 2% lidocaine + 1:80,000 adrenaline is commonly used, including in dental patients with underlying diseases for whom adrenaline in local anesthetics is problematic due to its vasoconstrictive effects, as the adrenaline concentration in dental local anesthetic cartridges in Japan is commercially set at 1:80,000. To reduce the effect of adrenaline on the cardiovascular system, adrenaline is sometimes diluted in dental local anesthetic cartridges. We have previously introduced a simple dilution method. However, this method requires the additional purchase of thin metal needles, which may be inconvenient for dentists who do not specialize in dental anesthesia. Here, we present a more practical dilution method that uses the inner needle of an intravenous catheter (22- or 24-G). Given that intravenous catheters are often kept in dental clinics for sedation or emergency use, we thought that this method would be more versatile. In this method, the inner needle of the intravenous catheter is attached to the syringe and 2% lidocaine without adrenaline is aspirated; then, the half-discarded cartridge is filled with it. A unique feature of this method is the use of an intravenous catheter, which many dental clinics keep on hand for intravenous sedation or emergencies during dental treatments. To safely administer local anesthesia during dental procedures, we propose a more practical and convenient method of diluting the adrenaline concentration in local anesthetic cartridges.