Cone-Beam Computed Tomography 1 Dental Pulp Cavity 1 Endodontic access cavity 1 Humans 1 Minimal invasive therapy 1 Molar 1 Radiography, Dental 1 Root Canal Preparation 1 Root Canal Therapy 1 Second mesiobuccally canal 1 Tooth, Nonvital 1 Upper molar article 1 chi square test 1 cone beam computed tomography 1 dental pulp cavity 1 diagnostic imaging 1 endodontic procedure 1 human 1 invasive procedure 1 maxillary first molar 1 molar tooth 1 preoperative evaluation 1 procedures 1 root canal preparation 1 surgery 1 tooth pulp disease 1 tooth radiography 1 tooth tissue 1