It should be kept in mind that when performing operative or endodontic procedures in young permanent mandibular molar with deep caries diagnosed as normal pulp, reversible pulpitis and irreversible pulpitis, most patients may experience pulpal anesthetic difficulty by IANB during treatment. Therefore, the dentists should be well prepared to deal with this problem. The use of sensibility tests is recommended to confirm pre-operative pulpal anesthesia. If patients still respond to the sensibility test pre-operatively, the supplemental injection such as SMBI with 4% articaine is necessary to improve pulpal anesthesia. We may expect a greater volume of 4% articaine can provide a higher pulpal anesthetic success rate. However, the anesthetic solutions must not exceed the calculated maximum dosage.