Discomfort during dental local anesthetic injections correlated to pressure at the start of injection

The injection pressure and discomfort at the start of injection of a local anesthetic into the oral mucosa were quantitatively assessed and their relationship verified. The subjects were 28 healthy adult males, and 30G x1/2" disposable needles and an electric type syringe were used. Three seconds after the start of the local anesthetic injection, the injection pressure was measured and discomfort was assessed. A volume of 0.5 ml of local anesthetic solution was injected submucosally at injection speeds of 30 or 160 sec/ml. The injection pressure was measured continuously in real time, using an invasive sphygmomanometer and analytical software. Discomfort was assessed using a Visual Analogue Scale. A significant correlation was evident between the intensity of discomfort and injection pressure (rs=0.51542, p=0.00500). According to the results of simple regression, there was a VAS-Discomfort score of 51 meaning that more than half of the VAS scores corresponded to the injection pressure of 348.1mmHg. It is therefore recommended that local anesthetic is injected at less than 348.1mmHg at the start of injection, to minimize discomfort for patients