Metronidazole for toothache mostly belongs to nitroimidazole antibiotics, which mainly treats anaerobic infections. Metronidazole can effectively kill Porphyromonas gingivalis, Porphyromonas intermedia, Clostridium nucleatum, Spirochetes and Streptococcus digestive, etc. It has good therapeutic effect on pulpitis and periodontitis caused by the above mentioned bacteria, and it can significantly reduce the Spirochetes and Clostridium nucleatum in the plaque and improve the pulpal congestion, periodontal pus overflow, and it can control the acute attack of inflammation. Metronidazole can specialize in killing anaerobic bacteria, not easy to cause dysbiosis, but also not easy to produce drug-resistant strains, can be combined with other drugs, such as amoxicillin, spiramycin, or tetracycline, to enhance the effect of bacterial inhibition.