Lesion Sterilization and Tissue Repair (LSTR) is also called NIET or NonInstrumental Endodontic Treatment as it claims to be a “new biologic approach in the treatment of carious lesions with periapical involvement using a mixture of 3 antibiotics (3- Mix).” LSTR involves the use of three antibiotics/antibacterial drugs namely, Metronidazole, Ciprofloxacin and Minocycline. This therapy aims to eliminate bacteria from the root canals by sterilizing the lesion and promoting tissue repair and regeneration by the host’s natural tissue responses. Present review of literature aims to discuss LSTR in details.