热病，肾绝，齿黄落，色如熟小豆，或齿忽变黑者死。久病龈肉软却；齿长而垢，或齿光无
垢者死。（此所谓大骨枯槁也。）口开，前板齿燥者，伤暑也。（《脉经》。）
齿龈无色，舌上尽白，唇里有疮者， 也。（按∶即狐惑也。出巢氏。）
温热病，看舌之后，亦须验齿。齿为肾之余，龈为胃之络。热邪不燥胃津，必耗肾液，且二经之血，皆
走其地，病深动血，结瓣于上。阳血者，色必紫，紫如干漆。阴血者，色必黄，黄如酱瓣。阳血若见，安胃
为主。阴血若见，救肾为要。然豆瓣色者，多险，若证还不逆者，尚可治，否
则，难为矣。何以故耶，盖阴下竭，阳上厥也。
齿若光燥如石者，胃热甚也，若无汗恶寒，卫偏
胜也，辛凉泄卫，透汗为要。若如枯骨色者，肾液枯也。若上半截润，（靠根半截。）水不上承，心火上
炎也，急急清心救水，俟枯处转润为妥。（此必充发水中真气，方能有效，非仅甘润凉降所能为也。）
若切牙啮齿者，湿热化风痉病。但切牙者，胃热气走其络也。若切牙而脉证皆衰者，胃虚无谷以内荣，
亦切牙也。何以故耶。虚则喜实也。舌本不缩而硬，而牙关咬定难开者，此非风痰阻络，即欲作痉证，
用酸物擦之即开，木来泄土故也。（风能化燥，酸即生津。）
若齿垢如灰糕样者，胃气无权，津亡，湿浊用事，多死。而初病齿缝流清血，痛者，胃火冲激也；不
痛者，龙火内燔也。（总是悍气，窜入血道。）齿焦无垢者，死，齿焦有垢者，肾热
劫胃也，当微下之，或玉女煎，清胃救肾可也。（《温热论》。）
齿根于冲督之脉，故小儿齿出迟者，以鹿茸、肉苁蓉服之。凡小儿齿出偏斜稀疏者，阳明本气不足也。
齿色枯白者，血虚也。齿色黄暗，或带黑，或片片脱下者，面色青黄，此腹中有久冷积，太阳阳明之阳气受
困，累及于冲督也。落齿后，久不出者，肾与督虚也，必重以鹿茸，加补冲督药，否则出必偏斜稀疏，甚者，
不久复碎落也。俗每以为血热，殊不知是虚冷久积，血不流通，内蓄虚火也。若有虫者是湿热，
亦因胃有积滞；若不虚冷，则面色自红润，不惨黯也。
热病过程中，若出现肾气衰竭的症状，牙齿发黄脱落，颜色像熟透的小豆，或者牙齿突然变黑的，预后不良，主死。久病患者如果牙龈萎缩退缩；牙齿显得过长且污垢堆积，或者牙齿光亮却没有污垢的，预后不良，主死。（这就是所说的“大骨枯槁”的表现。）嘴巴张开，门牙干燥的，是伤暑所致。（出自《脉经》。）
牙齿和牙龈颜色淡白无血色，舌面上全部发白，嘴唇里面有疮疡的，是狐惑病。（按：即狐惑病。出自巢元方的著作。）
在温热病中，观察舌象之后，也必须检查牙齿。牙齿是肾精之余气所生，牙龈是胃经之络脉所过之处。热邪如果不耗伤胃中的津液，就一定会消耗肾中的阴液，而且这两条经络的血气，都汇聚于齿龈部位，病情深重时动血，血液凝结成瓣状浮于上。阳血（属阳的热盛出血），颜色必定紫暗，像干漆一样；阴血（属阴的虚损出血），颜色必定黄淡，像酱瓣一样。见到阳血，治疗以安胃为主；见到阴血，治疗以救肾为要。然而，如果是豆瓣色（指阴血之色）的，大多危险，如果证候还没有逆乱，还可以治疗，否则就很难救治了。为什么呢？这是因为阴精在下枯竭，阳气在上厥逆的缘故。
如果牙齿光亮干燥像石头一样，是胃热很盛；如果没有汗且怕冷，是卫气偏胜，治疗应以辛凉药物疏散卫分邪气，透出汗液为关键。如果牙齿颜色像枯骨一样，是肾液枯竭。如果牙齿上半截湿润（靠近根部的一半），说明肾水不能上承，心火向上炎灼，必须紧急清心火、救肾水，等到干枯处转为湿润才稳妥。（这必须激发水中真气的升腾，才能有效，不仅仅是靠甘润凉降的药物所能做到的。）
如果出现咬牙或磨牙的现象，是湿热化风导致的痉病。只是咬牙的，是胃热之气窜入络脉所致。如果咬牙且脉象和证候都呈现衰微状态，是胃中虚无水谷精气来滋养，也会引起咬牙。为什么呢？因为虚证往往表现为喜实（虚极而现假实之象）。舌根不收缩但僵硬，牙关紧闭难以张开的，这不是风痰阻滞络脉，就是即将发生痉证，用酸味物质擦拭即可张开，因为木能泄土（酸属木，能制约脾土之壅滞）。（风能化燥，酸味能生津液。）
如果牙齿上的垢腻像灰糕一样，是胃气无权运化，津液亡失，湿浊邪气盛行，多主死亡。初病时牙齿缝隙流出清血，伴有疼痛的，是胃火冲激所致；不疼痛的，是龙火（相火）在内焚烧。（总是悍烈的邪气，窜入血脉之中。）牙齿焦黑没有垢腻的，主死；牙齿焦黑但有垢腻的，是肾热劫夺胃阴，应当轻微攻下，或者使用玉女煎，清胃热、救肾阴即可。（出自《温热论》。）
牙齿根源于冲脉和督脉，所以小儿出牙迟慢的，可以用鹿茸、肉苁蓉服用。凡是小儿出牙偏斜稀疏的，是阳明本气不足。牙齿颜色枯白的，是血虚。牙齿颜色黄暗，或者带黑色，或者成片脱落的，面色青黄，这是腹中有久冷的积滞，太阳和阳明的阳气受到困阻，累及到冲脉和督脉。牙齿脱落后，很久长不出来的，是肾与督脉虚弱，必须重用鹿茸，加上补益冲督的药物，否则新牙长出必偏斜稀疏，严重的，不久又会碎裂脱落。世俗人常以为是血热，殊不知这是虚冷久积，导致血行不畅，内部蓄积虚火所致。如果有虫蚀的情况，那是湿热，也是因为胃有积滞；如果不是虚冷，那么面色自然会红润，不会惨暗。
In the course of febrile diseases, if signs of Kidney Qi exhaustion appear—such as teeth turning yellow and falling out with a color resembling ripe small beans, or teeth suddenly turning black—the prognosis is poor, indicating death. In chronic illnesses, if the gingival tissue recedes; the teeth appear elongated with accumulated plaque, or the teeth are shiny but devoid of plaque—the prognosis is poor, indicating death. (This is referred to as "withered large bones.") Mouth opening with dry incisors indicates damage from summerheat. (*Mai Jing*.)
Teeth and gums lacking color, the entire tongue surface being white, and sores inside the lips indicate Hu Huo Disease (Foxes Disease, characterized by oral and genital ulcers). (Note: This refers to Hu Huo Disease. Originating from Chao Yuan-fang's works.)
In warm-heat diseases, after examining the tongue, one must also inspect the teeth. Teeth are the surplus of Kidney essence; gums are the network vessels of the Stomach channel. If pathogenic heat does not dry up Stomach fluids, it will inevitably consume Kidney yin. Furthermore, the blood of these two meridians flows into this area. When the disease is deep and moves the blood, coagulated blood forms瓣 (petals/clots) on the upper part. Yang-type bleeding (bleeding due to excess heat) will be purple in color, like dried lacquer. Yin-type bleeding (bleeding due to deficiency) will be yellowish, like soybean paste. If Yang-type bleeding is observed, treatment should focus on stabilizing the Stomach. If Yin-type bleeding is observed, saving the Kidney is essential. However, cases presenting with a soybean-paste color are mostly dangerous; if the syndrome has not yet become rebellious, it may still be treatable; otherwise, it is difficult to manage. Why? Because this is due to exhaustion of Yin below and rebellion of Yang above.
If teeth are shiny and dry like stone, it indicates severe Stomach heat. If there is no sweat and aversion to cold, it indicates an excess of Wei (Defensive) Qi; treatment should prioritize using acrid-cool herbs to vent the Defensive level and induce sweating. If teeth resemble the color of dry bones, it indicates exhaustion of Kidney fluids. If the upper half of the teeth is moist (the half near the root), it indicates that Kidney water fails to ascend, and Heart fire flares upward. Urgent clearing of Heart fire and rescue of Kidney water are required, waiting until the dry areas become moist again for safety. (This requires stimulating the true Qi within Water to ascend; it cannot be achieved merely by sweet-moistening and cooling-descending herbs.)
If teeth grinding or clenching occurs, it indicates a spasm disease caused by damp-heat transforming into wind. Mere tooth clenching indicates Stomach heat qi invading the collaterals. If tooth clenching occurs alongside weak pulse and symptoms, it indicates Stomach deficiency where grain essence fails to nourish internally, which also causes clenching. Why? Because extreme deficiency often manifests as apparent excess. If the root of the tongue is stiff without shrinking, and the jaw is locked tight and difficult to open, this is either wind-phlegm obstructing the collaterals or impending spasm disease. Rubbing with sour substances can open the jaw because Wood drains Earth. (Wind transforms into dryness; sour flavors generate body fluids.)
If dental plaque resembles gray cake, it indicates loss of Stomach Qi authority, depletion of fluids, and dominance of turbid dampness, usually leading to death. In early-stage disease, clear blood flowing from between teeth accompanied by pain indicates Stomach fire rushing and striking; absence of pain indicates internal blazing of Dragon Fire (Ministerial Fire). (This is always fierce pathogenic qi intruding into the blood vessels.) Teeth scorched black without plaque indicate death; teeth scorched black with plaque indicate Kidney heat robbing Stomach yin; mild purgation should be used, or Yü Nv Jian (Jade Woman Decoction) to clear Stomach heat and rescue Kidney yin. (*Wen Re Lun*.)
Teeth originate from the Chong and Du vessels. Therefore, children with delayed tooth eruption can be treated with Lu Rong (Deer Antler) and Rou Cong Rong (Cistanche). Children whose teeth erupt obliquely or sparsely suffer from insufficiency of the Yangming primary Qi. Teeth withered and white indicate Blood deficiency. Yellow-dark teeth, or those with black discoloration, or shedding in patches, accompanied by a blue-yellow complexion, indicate long-standing cold accumulation in the abdomen. The Yang Qi of Taiyang and Yangming is constrained, affecting the Chong and Du vessels. After tooth loss, if new teeth fail to emerge for a long time, it indicates deficiency of the Kidney and Du vessel. Heavy use of Lu Rong (Deer Antler) combined with herbs tonifying the Chong and Du vessels is necessary; otherwise, emerging teeth will be oblique and sparse, and severely, they may crumble and fall out shortly thereafter. Laypeople often attribute this to Blood heat, unaware that it is actually long-standing deficiency-cold causing stagnant Blood and internal accumulation of deficient fire. Presence of dental caries indicates damp-heat, also due to food stagnation in the Stomach; if not deficiency-cold, the complexion would naturally be ruddy and vibrant, not dull and dark.