It is best to choose the morning for tooth extraction, because in the morning, a person’s blood pressure, blood sugar and overall physical condition are more stable, and the chances of complications during and after the extraction are significantly reduced. Before the extraction of teeth should be done routine blood and coagulation routine checks, if the blood pressure is too high when the extraction of teeth, it is easy to lead to bleeding after the extraction of teeth. If the tooth is extracted when the blood sugar is not well controlled, it is easy to cause infection of the wound after the extraction. When there is pain and infection in the teeth can not be extracted, such as in the acute attack of wisdom teeth pericoronitis, this time can not be extracted, extracting the teeth will cause the spread of inflammation, resulting in facial swelling, infection, only when the pain and infection of the teeth can be extracted after the complete control of the teeth. Extraction is also not recommended when the patient has acute inflammation, blood system diseases, chronic liver disease, cardiovascular and cerebrovascular diseases, renal dysfunction, as well as women’s menstrual period.