Deflection of Needles, Used for Local Anesthesia in the Dental Practice – Comparative Study

The mandibular nerve blocks prove to be one of the most challenging anesthetic techniques for the dental practitioner. Many factors have a role in the success of these nerve blocks and one of them is the accuracy of the deposition of the anesthetic which can be influenced to a certain degree by the deflection of the injection needle. In this study, three types of injection needles (Septoject XL 30G, Septoject XL 27G and Medoject 23G) were tested for deflection in a reversible hydrocolloid (agar-agar). They were divided into three groups of 30 needles each and were all inserted in the agar-agar at a depth of 20 mm with the help of a dental surveyor. Two mutually perpendicular radiographs were made for each needle in order to calculate the deviation in mm. The results were analyzed and showed that the mean deflection in the 30G needles group was 5.32±1.91 mm, the deviation in the 27G group – 3.37±0.67 mm and none of the needles in the 23G group showed a deviation upon insertion in the hydrocolloid. The results in this study showed that dentists should always prefer needles with a smaller gauge, because they provide smaller deflection figures and therefore better accuracy in the deposition of the anesthetic.