BACKGROUND: Inferior alveolar nerve block (IANB) of the mandible is commonly used in the oral cavity as an anesthetic technique for dental procedures. This study evaluated the success rate of the first IANB administered by dental practitioners. METHODS: Volunteer dental practitioners at Mahidol University who had never performed an INAB carried out 106 INAB procedures. The practitioners were divided into 12 groups with their advisors by randomized control trials. We recorded the success rate via pain visual analog scale (VAS) scores. RESULTS: A large percentage of the dental practitioners (85.26%) used the standard method to locate the anatomical landmarks, injecting the local anesthetic at the correct position, with the barrel of the syringe parallel to the occlusal plane of the mandibular teeth. Further, 68.42% of the dental practitioners injected the local anesthetic on the right side by using the left index finger for retraction. The onset time was approximately 0-5 mins for nearly half of the dental practitioners (47.37% for subjective onset and 43.16% for objective onset), while the duration of the IANB was approximately 240-300 minutes (36.84%) after the initiation of numbness. Moreover, the VAS pain scores were 2.5 ± 1.85 and 2.1 ± 1.8 while injecting and delivering local anesthesia, respectively. CONCLUSIONS: The only recorded factor that affected the success of the local anesthetic was the administering practitioner. This reinforces the notion that local anesthesia administration is a technique-sensitive procedure.