The oral and maxillofacial areas are located at the beginning of the respiratory and digestive tracts and are directly connected to the external environment through the nasal and oral cavities. At the same time, the special anatomical structure of the oral cavity, nasal cavity, paranasal sinus, teeth, gums and tonsils, as well as the temperature (35-36℃) and humidity of these parts are suitable for bacteria to “settle” here, plus the oral cavity The mouth can provide a complex of bacteria, fungi, mycoplasma, protozoa and viruses. These microorganisms find “residence” in different places in the oral cavity, and help each other, mutual restraint, and the oral cavity constitutes the most complex ecology of the human oral microecological system, and often maintain a dynamic balance between microorganisms, microorganisms and the human oral cavity. But if the external or internal (human body itself) environmental changes, such as local injury, surgery, diet, hygiene habits change, their own resistance to decline, are prone to cause disease due to dysbiosis of the flora. In addition, the facial skin frontal hair follicles, sweat glands, sebaceous glands are also places where bacteria reside, if local injury, poor hygiene, local or systemic resistance is reduced, it is also easy to attract infection.