Soft tissues in the oral cavity mainly include periodontal tissues, oral mucosa and tongue. Periodontal tissue refers to the alveolar bone, periodontal membrane and gums, which is the foundation for teeth to survive and perform normal physiological functions, just like the foundation of a ten-thousand-foot tall building. If the periodontal tissues are diseased, the function of the teeth will be greatly weakened, the teeth will start to loosen, painful and weak to bite, and if the periodontal tissues are completely lost, the teeth will fall out by themselves. Periodontal disease is the number one killer of tooth loss, and in modern dentistry, maintenance of healthy periodontal tissue and early control of periodontal disease are seen as the most important measures to maintain dental health. The periodontium is a dense connective tissue located between the roots of the teeth and the alveolar bone, and is composed mainly of collagen fibers. It acts as a spring that suspends the tooth in the socket, giving it the ability to withstand the pressure of chewing and relieving the trauma to the alveolar bone from the pressure impact, thus, protecting the alveolar bone. The periodontal membrane is rich in nerve receptors that are very sensitive to pain, pressure and vibration. These receptors form a reflex arc with the neuromuscles that regulate biting and chewing movements randomly or non-randomly. The gingiva surrounds the neck of the teeth and covers the surface of the alveolar ridge, a pink oral mucosa with a tough texture and little mobility. Depending on the location, the gingiva is divided into free gingiva, attached gingiva and interdental papillae. The intrinsic layer of the attached gingiva is directly attached to the alveolar bone and the cervical part of the tooth, and its dense connective tissue, rich in collagen fibers, keeps the gingiva firmly attached to the deeper tissues. The interdental papillae are located between adjacent teeth and fill the interstitial space. Atrophy of the interdental papillae can cause food impaction. Gums, periodontium and alveolar bone are closely related to each other, and only when they are all healthy can the teeth be stable and secure, and the functions of the teeth can be performed normally. Oral mucosa is divided into masticatory mucosa, covered mucosa and special mucosa according to their functions. The masticatory mucosa covers the hard palate and most of the gingival surface, with little mobility and epithelial keratinization. Covered mucosa plays a covering role, such as the mucosa of the buccal, labial, migratory sulcus, floor of the mouth, tongue belly and soft palate all belong to the covered mucosa. The dorsal mucosa of the tongue is a special mucosa. Oral mucosa has barrier function, sensory function, immune function and digestive aid function. The tongue is located on the inner side of the dentition, and the longitudinal and transverse muscle fibers in the tongue have an extremely flexible and convenient shape and movement. The tongue has a lot of roles, our pronunciation is inseparable from the tongue; chewing and swallowing are closely related; and the most enjoyable role of the tongue is to feel and other functions. The mucous membrane on the surface of the tongue is papillary in shape. The ventral surface of the tongue has a lingual ligament, and there are sublingual veins and sublingual glands on both sides. There are four basic forms of lingual papillae, called filiform papillae, fungiform papillae, contoured papillae and lobulated papillae. Filiform papillae are the most numerous and are found throughout the tongue. The mycotic papillae are more numerous and are scattered between the filiform papillae. The contour papillae are located between the tongue body and the tongue root and are large and protrude significantly, usually 7-9. The lobular papillae are located at the lateral edge of the tongue body. Have you ever wondered how our “three-inch tongue” perceives the delicious food and wine? As mentioned earlier, the surface of the tongue is the lingual papillae, which are rich in taste receptors. Taste receptors, also known as taste buds, are also found in the mucosal epithelium of the soft palate, pharynx and epiglottis. It is through the taste receptors, i.e., taste buds, that we perceive and enjoy these delicacies. In fact, the taste buds receive only four basic taste sensations: sour, sweet, bitter and salty, while other taste sensations such as numbness and spiciness are formed by the interplay of these four basic taste sensations. In different parts of the tongue, these four basic taste sensations show different degrees of sensitivity: the tip of the tongue is most sensitive to sweetness, the root of the tongue is sensitive to bitterness, the lateral edge of the tongue is sensitive to sourness, and all parts of the tongue are very sensitive to saltiness. The mucous membrane epithelium of the tongue is thin and transparent, extremely sensitive to internal and external stimuli, and the tongue is rich in blood vessels, many systemic diseases and pathological changes can be reflected through the tongue mucosa, therefore, Chinese medicine has long used the tongue as an important window to “look at the disease”, so there is a close link between systemic diseases and the tongue.