en Oral medicine Oral medicine Original article Original article <strong>Background and Aim</strong>: The Gow-Gates (GG) block and the inferior alveolar nerve block (IANB) can be used interchangeably for anesthetizing mandibular molars. The aim of this study was to compare these two injections in root canal therapy of mandibular molars with regard to heart rate (HR) and blood oxygen saturation (BOS) changes.<br> <strong>Materials and Methods</strong>: Thirty patients between the ages of 18-70 years having mandibular molars on both sides of their jaw and in need of root canal therapy were recruited after signing a consent form. The patients&#39; HR and BOS were measured 5 minutes before and immediately, 2, 5, 10, 15, and 20 minutes after injection by using a pulse oximeter. Paired t-test and Friedman test were used for statistical analysis of the data. <span dir="RTL"></span><br> <strong>Results</strong>: This study was done on 30 patients (60 teeth). The results of HR and BOS showed no significant differences between the two injection techniques (P=0.6 and 0.7, respectively). Also, HR and BOS in each group were not significantly changed during the follow-ups (P=0.7 and 0.6, respectively).<br> <strong>Conclusion</strong>: According to the results, IANB and GG block by using 2% lidocaine and 1:80000 epinephrine had no significant different effects on HR and BOS. ضربان قلب, درصد اکسیژن اشباع خون, بلاک عصب آلوئولار تحتانی, GowGates Heart rate, Oximetry, Inferior alveolar nerve, Local anesthesia, Lidocaine 9 13 http://jrdms.dentaliau.ac.ir/browse.php?a_code=A-10-596-1&slc_lang=en&sid=1 M Vatanpour 100319475328460010661 100319475328460010661 No Assistant professor, Endodontics Dept,Dental Branch of Tehran, Islamic Azad University, Tehran, Iran N Roghanizad 100319475328460010662 100319475328460010662 No Assistant professor, Endodontics Dept,Dental Branch of Tehran, Islamic Azad University, Tehran, Iran D bineshmarvasti dlrmbm@yahoo.com 100319475328460010663 100319475328460010663 Yes postgraduate Postgraduate Student , Endodontics Dept, Dental Branch of Tehran, Islamic Azad University, Tehran, Iran R Hosseini 100319475328460010664 100319475328460010664 No Dentist P Mohebbi 100319475328460010665 100319475328460010665 No Dentist