In the process of oral local anesthesia, the following complications may occur: 1, the injection process will be injected into the blood vessels, a sudden increase in the concentration of local anesthetics in the blood, will lead to local anesthetic poisoning; 2, the implementation of local anesthesia, if penetrating the blood vessels, will lead to local hematoma; 3, local anesthetic drug injection site is not accurate, resulting in poor anesthesia; 4, the more serious condition is hypersensitive patients, more sensitive to drugs, can appear allergic reactions, this condition is relatively rare.