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Apply a fine powder of *Cicadae Periostracum* (Chanke, 蝉壳) mixed with honey and pig bile to the swollen area.

Li Dongyuan stated: The teeth are the external manifestation of the Kidney (Shen, 肾), and the mouth is the orifice of the Spleen (Pi, 脾). Many meridians converge in the mouth, including those related to the teeth. The Hand-Yangming Large Intestine Meridian (Shou Yangming Dachang Jing, 手阳明大肠经) and Foot-Yangming Stomach Meridian (Zu Yangming Weijing, 足阳明胃经) pass through this region. The upper gums belong to the Kun position (inferior aspect) and are connected by the Foot-Yangming Stomach Meridian, whose qi remains relatively static. The lower gums are involved in chewing and move constantly, connected by the Hand-Yangming Large Intestine Meridian. The Hand-Yangming meridian dislikes cold and prefers warm drinks; the Foot-Yangming meridian likes cold and dislikes hot drinks; their pathologies differ. As the external manifestation of the Kidney, the teeth also prefer cold, which ensures firmness, yet the pathological conditions vary. Excessive heat causes tooth mobility and gum recession, leading to persistent pain; thus, treatments differ. Some experience pain triggered by cold objects, some by hot objects, some by both, some by drinking little cold water but much hot water, and some by drinking little hot water but much cold water. Others suffer pain due to tooth mobility, gum recession, tooth decay with bleeding, gum swelling, or wind-pathogen in the Spleen and Stomach causing pain upon exposure to wind. Additionally, teeth may be eroded by "worms" (dental caries), becoming loose, discolored, and painful; or pain may arise from deficient Stomach Qi failing to ward off cold, exposing the teeth; or pain may be accompanied by foul odor intolerable to others. Since the causes of pain are diverse, how can one single remedy suffice? Generally, various dental pains stem from excessive Stomach Fire (Wei Huo, 胃火). Teeth are the essence of bones, governed by the Kidney. The outer hard layer is the tooth crown, while the inner bed is the root. Strong Kidney Qi ensures firm teeth; weak Kidney Qi leads to dental disease. The Hand-Yangming meridian passes through the cheek into the lower interdental space, irrigating the teeth. If wind-cold obstructs heat qi, or stagnation occurs in the chest, rising to the mouth, it causes dental issues: mild cases present as exposed teeth and swollen gums/cheeks; severe cases manifest as canker sores, caries, and tooth loss. Dental diseases primarily involve the Hand-Yangming and Foot-Yangming meridians, with tooth mobility and gum recession also involving the Foot-Shaoyin Kidney Meridian (Zu Shaoyin Shenjing, 足少阴肾经); thus, these three meridians are most relevant. However, exposed teeth, worm-eaten cankers, damp-heat gum swelling, bleeding pain, and foul-smelling pain are all caused by excessive Stomach Fire and Heat. There are also cases involving mixed pathogens from other meridians or external factors, which students should investigate deeply. Chen Wuyue said: Teeth are the guards of the gate, the glory of the Kidney, and the surplus of bone. When Kidney Qi declines, teeth become loose; when essence is secured, teeth remain firm. Furthermore, collateral branches of the Large Intestine reside in the gums, irrigating the teeth. Large Intestine stagnation causes floating teeth; deficiency causes exposed teeth; if complicated by wind, it attacks the eyes, causing facial swelling and irregular movements. Li Dongyuan also recounted: A official named Liu, aged thirty-something, suffered unbearable toothache. He had to ride a horse outside, inhaling cool air, which immediately relieved the pain, but it returned home. His family thought it was a spirit possession and prayed to a shaman without success. The disease was actually caused by damp-heat pathogen. The Foot-Yangming Stomach Meridian has abundant blood and qi; combined with rich, greasy foods, it exacerbates damp-heat, causing this pain. Therefore, he formulated a prescription that does not require riding a horse, aiming to generate a cooling sensation in the teeth: using the bitter-cold properties of *Coptidis Rhizoma* (Huanglian, 黄连) and *Tamarisci Caulis* (Hutonglei, 胡桐泪), combined with the acrid-cool properties of fresh *Menthae Haplocalycis Herba* (Bohe, 薄荷) and *Schizonepetae Spica* (Jingjie, 荆芥). These four ingredients create a cooling effect to treat damp-heat as the primary focus. Fresh *Bupleuri Radix* (Shengma, 升麻) acts as the guiding drug for the Yangming meridian. Since teeth are the surplus of bone, *Ossus Tibiae Caprae* (Yangjinggu, 羊胫骨) ash is used as an adjuvant to tonify. A small amount of *Moschus* (Shexiang, 麝香) serves as a guide to penetrate tissue. All are ground into a fine powder and applied to rub the teeth, reducing pain by half. Subsequently, *Tiaowei Chengqi Tang* (Regulate the Stomach and Direct Downward Decoction) was modified by removing *Natrii Sulfas* (Mangxiao, 芒硝) and adding *Coptidis Rhizoma* to treat the root cause. After two to three bowel movements, the pain healed completely and did not recur. Thus, previous physicians used acrid-cool wind-dispelling agents, where wind overcomes dampness, and bitterness drains heat. In common practice, some boil *Genkwa Flos* (Yuanhua, 芫花), *Kansui Radix* (Daji, 大戟), *Triticum aestivum* (Xiaomai, 小麦), *Zanthoxyli Fructus* (Chuanjiao, 川椒), *Asari Radix et Rhizoma* (Xixin, 细辛), and *Atractylodis Macrocephalae Rhizoma* (Can'erzi, 苍耳子) decoction, rinsing the mouth while hot to stop toothache instantly. There are indeed many causes of dental disease internally, such as qi stagnation and blood heat, compounded by fried foods or tastes like cold water, salty/sour, or spicy flavors, which may soak and bind the tissues. Just as vinegar dissolves stone, how much more would it affect human bone surplus? Although meridians have different preferences for cold and heat, and disease origins vary between deficiency and excess, students who thoroughly study this theory will achieve therapeutic success soon.