In most cases, systemic antibiotics are not required in the clinical practice of endodontics. In a few cases, a dose of antibiotics is required, such as acute periapical abscesses with some systemic symptoms; interstitial infections; or prophylactic medication for poor systemic status. For infected patients with systemic symptoms, the main treatment is to remove the source of infection (cleaning the infected root canal), and in general, adequate chemical and mechanical preparation of the infected root canal can effectively relieve the patient’s clinical symptoms, and scientific drainage can also quickly relieve the patient’s clinical discomfort. If the patient’s symptoms worsen after the above treatment, antibiotics may be applied as appropriate. We may apply antibiotics in the following cases, where we have performed root canal preparation and root canal disinfection, and the patient still continues to have systemic symptoms, such as persistent high fever, intense discomfort, cellulitis, dental closure, and persistent significant swelling. Whenever possible, the identification of the infecting bacterial species and the corresponding antibiotic sensitivity test should be performed before applying antibiotics to the patient In some cases, prophylactic application of antibiotics is required, and the patient should be consulted with a specialist in the relevant disease. These include patients who are on long-term immunosuppression after organ transplantation, immunocompromised patients, diabetic patients, malnourished patients, and patients with hemophilia. The prophylactic regimen is: 2g of amoxicillin one hour before root canal treatment, and if the patient is allergic to amoxicillin, cefadroxil 600mg. We do not advocate that antibiotics should be used in the following cases: pulpitis, acute periapical inflammation, and periapical abscess incision without systemic symptoms. Generally speaking, the application of antibiotics is contraindicated in cases with normal immunity and no obvious clinical signs of infection, swelling, etc.