Laminated root rot also known as yellow ring rot is caused by the fungal pathogen "Phellinus weirii". Laminated root rot is one of the most damaging root disease amongst conifers in northwestern America and true firs, Douglas-fir, Mountain hemlock, and Western hemlock are highly susceptible to infection with "P. weirii". A few species of plants such as Western white pine and Lodgepole pine are tolerant to the pathogen while Ponderosa pine is resistant to it. Only hardwoods are known to be immune to the pathogen.

The disease can infect trees as young as 6 years-old, and infects trees throughout their lifespan. Diagnostic symptoms include crown yellowing and thinning, a distress crop of cones, red brown stained outer heartwood, and laminate decay (decay that separates along annual rings). The disease tends to occur in patches due to a primarily short range spread mechansism. Infected or decayed roots break close to the root collar forming “root balls.” Laminated root rot is frequently detected during ground survey when canopy openings and standing dead and fallen trees are observed. Signs of laminated root rot include the setal hyphae (tiny hairlike hyphae) between sheets of decomposing wood and also buff-colored mycelium on the outside of the roots.

The foamy bark canker is a disease affecting oak trees in California caused by the fungus "Geosmithia pallida" and spread by the Western oak bark beetle ("Pseudopityopthorus pubipennis"). This disease is only seen through the symbiosis of the bark beetles and the fungal pathogen. The bark beetles target oak trees and bore holes through the peridermal tissues, making tunnels within the phloem. The fungal spores are brought into these tunnels by the beetles and begin to colonize the damaged cells inside the tunnels. Symptoms of the developing fungus include wet discoloration seeping from the beetle entry holes as the fungus begins to consume phloem and likely other tissues. If bark is removed, necrosis of the phloem can be observed surrounding the entry hole(s). As the disease progresses, a reddish sap and foamy liquid oozes from entry holes, thus giving the disease the name Foamy bark canker. Eventually after the disease has progressed, the tree dies. This disease is important because of its detrimental effects on oak trees and its ability to spread to several new Californian counties in just a couple years.

Cyclaneusma (needle cast) is a fungal disease that is a part of the phylum, Ascomycota. It infects plants that are of pine classification. After infection by "Cyclaneusma", most pines do not display symptoms until 10 months after the initial infection. Symptoms include needles developing yellow spots, horizontal brown bands around the needles, swelling of needles, and off-white fruiting bodies formed on infected needles. Because "Cyclaneusma" is an ascomycete it produces two spore types, an asexual (conidiomata) and sexual (ascomycota) spore. Controlling "Cyclaneusma" has presented a challenge as the disease can survive on both living and dead needles during the winter months. Effective management methods include planting new pines in non-shaded, well drainable soil as well as spraying fungicide. "Cyclaneusma" Needle Cast is an important fungal disease because it directly impacts the commercial value of decorative pines as well as lumber.

STK typically occurs in the buccal sulcus (inside the cheek) or the labial sulcus (between the lips and the teeth) and corresponds to the site where the tobacco is held in the mouth. It is painless.

The appearance of the lesion is variable depending upon the type of tobacco used, and the frequency and duration of use. It takes about 1-5 years of smokeless tobacco use for the lesion to appear. Early lesions may appear as thin, translucent and granular or wrinkled mucosa. The later lesion may appear thicker, more opaquely white and hyperkeratotic with fissures and folds. Oral snuff causes more pronounced changes in the oral mucosa than tobacco chewing. Snuff dipping is associated more with verrucous keratosis.

As well as the white changes of the oral mucosa, there may be gingival recession (receding gums) and staining of tooth roots in the area where the tobacco is held.

Hosts associated with "Geosmithia pallida" include a number of tree species, including oak and other hardwoods, pine and spruce trees, depending on the beetle vector. In this case, the western oak bark beetles target live oak trees of western United States. Beetles tend to attack stressed trees that are already weakened from drought or injury. Symptoms causing branch dieback and tree death also include a cinnamon-colored gum seeping from multiple beetle entry holes on the bole, followed by a prolific, cream-colored foamy liquid. These symptoms, as well as signs (entry holes, larvae, beetles) of bark beetles, are key factors in diagnosis. Necrosis of xylem and phloem tissues underneath bark can be observed.

Common Symptoms:

- Wet discoloration on bark

- Phloem necrosis

- Beetle entry holes

- Reddish sap oozing from entry holes

- Foamy liquid from entry holes

A tree nut allergy is a hypersensitivity to dietary substances from tree nuts and edible tree seeds causing an overreaction of the immune system which may lead to severe physical symptoms. Tree nuts include, but are not limited to, almonds, Brazil nuts, cashews, chestnuts, filberts/hazelnuts, macadamia nuts, pecans, pistachios, pine nuts, shea nuts and walnuts.

Tree nut allergies are distinct from peanut allergy, as peanuts are legumes, whereas a tree nut is a hard-shelled nut.

True hyposalivation may give the following signs and symptoms:

- Dental caries (xerostomia related caries) – Without the anticariogenic actions of saliva, tooth decay is a common feature and may progress much more aggressively than it would otherwise ("rampant caries"). It may affect tooth surfaces that are normally spared, e.g., cervical caries and root surface caries. This is often seen in patients who have had radiotherapy involving the major salivary glands, termed radiation-induced caries.

- Acid erosion. Saliva acts as a buffer and helps to prevent demineralization of teeth.

- Oral candidiasis – A loss of the antimicrobial actions of saliva may also lead to opportunistic infection with "Candida" species.

- Ascending (suppurative) sialadenitis – an infection of the major salivary glands (usually the parotid gland) that may be recurrent. It is associated with hyposalivation, as bacteria are able to enter the ductal system against the diminished flow of saliva. There may be swollen salivary glands even without acute infection, possibly caused by autoimmune involvement.

- Dysgeusia – altered taste sensation (e.g., a metallic taste) and dysosmia, altered sense of smell.

- Intraoral halitosis – possibly due to increased activity of halitogenic biofilm on the posterior dorsal tongue (although dysgeusia may cause a complaint of nongenuine halitosis in the absence of hyposalivation).

- Oral dysesthesia – a burning or tingling sensation in the mouth.

- Saliva that appears thick or ropey.

- Mucosa that appears dry.

- A lack of saliva pooling in the floor of the mouth during examination.

- Dysphagia – difficulty swallowing and chewing, especially when eating dry foods. Food may stick to the tissues during eating.

- The tongue may stick to the palate, causing a clicking noise during speech, or the lips may stick together.

- Gloves or a dental mirror may stick to the tissues.

- Fissured tongue with atrophy of the filiform papillae and a lobulated, erythematous appearance of the tongue.

- Saliva cannot be "milked" (expressed) from the parotid duct.

- Difficulty wearing dentures, e.g., when swallowing or speaking. There may be generalized mucosal soreness and ulceration of the areas covered by the denture.

- Mouth soreness and oral mucositis.

- Lipstick or food may stick to the teeth.

- A need to sip drinks frequently while talking or eating.

- Dry, sore, and cracked lips and angles of mouth.

- Thirst.

However, sometimes the clinical findings do not correlate with the symptoms experienced. E.g., a person with signs of hyposalivation may not complain of xerostomia. Conversely a person who reports experiencing xerostomia may not show signs of reduced salivary secretions (subjective xerostomia). In the latter scenario, there are often other oral symptoms suggestive of oral dysesthesia ("burning mouth syndrome"). Some symptoms outside the mouth may occur together with xerostomia.

These include:

- Xerophthalmia (dry eyes).

- Inability to cry.

- Blurred vision.

- Photophobia (light intolerance).

- Dryness of other mucosae, e.g., nasal, laryngeal, and/or genital.

- Burning sensation.

- Itching or grittiness.

- Dysphonia (voice changes).

There may also be other systemic signs and symptoms if there is an underlying cause such as Sjögren's syndrome, for example, joint pain due to associated rheumatoid arthritis.

There are many types of smokeless tobacco. Chewing tobacco is shredded, air-cured tobacco with flavoring. Dipping tobacco ("moist snuff") is air or fire-cured, finely cut tobacco. Dry snuff is ground or pulverised tobacco leaves. In the Indian subcontinent, the Middle-East and South-East Asia, tobacco may be combined in a quid or paan with other ingredients such as betel leaf, Areca nut and slaked lime. Use of Areca nut is associated with oral submucous fibrosis. An appearance termed Betel chewer's mucosa describes morsicatio buccarum with red-staining of mucosa due to betel quid ingredients. In Scandinavian countries, snus, a variant of dry snuff, is sometimes used. In the United States of America, the most common form of smokeless tobacco is dipping tobacco, although chewing tobacco is sometimes used by outdoor workers and dry snuff is common among females in the Southern states. The overall prevalence of smokeless tobacco use in the USA is about 4.5%, but this is higher in Mid-Western and Southern states.

Xerostomia, also known as dry mouth and dry mouth syndrome, is dryness in the mouth, which may be associated with a change in the composition of saliva, or reduced salivary flow, or have no identifiable cause.

This symptom is very common and is often seen as a side effect of many types of medication. It is more common in older people (mostly because this group tend to take several medications) and in persons who breathe through their mouths (mouthbreathing). Dehydration, radiotherapy involving the salivary glands, and several diseases can cause hyposalivation or a change in saliva consistency and hence a complaint of xerostomia. Sometimes there is no identifiable cause, and there may be a psychogenic reason for the complaint.

Methamphetamine (meth), a psychologically addictive drug that produces a sharp increase in energy and possible euphoria, can have negative health effects that include serious dental problems. , it is the most discussed illegal drug in dental literature. The most notable effect of long-term use of methamphetamine on dental health is the development of caries (tooth decay); the teeth of some drug users appear to be dark and in the process of disintegrating. Caries often occur in the cervical regions of teeth, where the tooth surface narrows at the junction of the crown and the root. It is usually found on the buccal (cheek) side of the teeth and on tooth surfaces that are adjacent to incisors and canines; eventually, the coronal tooth area, near the crown, can be affected by the decay and erosion. The dental caries of meth mouth often progress slowly, perhaps because their advancement is hindered by intermittent hygienic practices. The decay can lead to tooth fractures and severe pain. In some cases, teeth are permanently damaged and must be removed. Along with malnutrition and weight loss, the dental effects of methamphetamine use contribute to the appearance of premature aging seen in some users. The effects of meth mouth are similar to those of Sjögren's syndrome, an autoimmune disease that causes a lack of saliva, which results in tooth decay.

Methamphetamine users sometimes experience soreness in the joint of the jaw and dental attrition (tooth wear), owing to bruxism (grinding of the teeth) caused by the drug. This bruxism can occur continuously. Chronic use of the drug might also cause trismus, the inability to open the jaw. Long-term users often experience xerostomia (dry mouth).

The Newton classification divides denture-related stomatitis into three types based on severity. Type one may represent an early stage of the condition, whilst type two is the most common and type three is uncommon.

- Type 1 - Localized inflammation or pinpoint hyperemia

- Type 2 - More diffuse erythema (redness) involving part or all of the mucosa which is covered by the denture

- Type 3 - Inflammatory nodular/papillary hyperplasia usually on the central hard palate and the alveolar ridge

A superior mouth is a mouth that opens upward, with the lower jaw more anterior than the upper jaw. This is an effect typically seen in fish. Some humans are born with this defect, often making their face resemble a shark's. This usually means that the fish feeds from the surface of the body of water in which it dwells.

By definition, BMS has no signs. Sometimes affected persons will attribute the symptoms to sores in the mouth, but these are in fact normal anatomic structures (e.g. lingual papillae, varices). Symptoms of BMS are variable, but the typical clinical picture is given below, considered according to the Socrates pain assessment method (see table). If clinical signs are visible, then another explanation for the burning sensation may be present. Erythema (redness) and edema (swelling) of papillae on the tip of the tongue may be a sign that the tongue is being habitually pressed against the teeth. The number and size of filiform papillae may be reduced. If the tongue is very red and smooth, then there is likely a local or systemic cause (e.g. eythematous candidiasis, anemia).

Despite the alternative name for this condition, "denture sore mouth", it is usually painless and asymptomatic. The appearance of the involved mucosa is erythematous (red) and edematous (swollen), sometimes

with petechial hemorrhage (pin-points of bleeding). This usually occurs beneath an upper denture. Sometimes angular cheilitis can coexist, which is inflammation of the corners of the mouth, also often associated with "Candida albicans". Stomatitis rarely develops under a lower denture. The affected mucosa is often sharply defined, in the shape of the covering denture.

Meth mouth is severe tooth decay and tooth loss, as well as tooth fracture, acid erosion, and other oral problems, potentially symptomatic of extended use of the drug methamphetamine. The condition is thought to be caused by a combination of side effects of the drug (clenching and grinding of teeth, dry mouth) and lifestyle factors (infrequent oral hygiene, frequent consumption of sugary drinks, as well as neglecting regular dental cleanings and preventative care), which may be present in long term users. However, the legitimacy of meth mouth as a unique condition has been questioned because of the similar effects of some other drugs on teeth. Images of diseased mouths are often used in anti-drug campaigns.

The condition is difficult to treat, and may involve fillings, fluoride to fight tooth decay and drugs that increase saliva for dry mouth, as well as oral hygiene instruction. It can be medically dangerous for active methamphetamine users because of the cardiac problems that can result from the interaction of local anesthetic with the drug.

Burning mouth syndrome (BMS) is a burning sensation in the mouth with no underlying dental or medical cause. No related signs of disease are found in the mouth. People with burning mouth syndrome may also have a dry mouth sensation where no cause can be found such as reduced salivary flow, tingling in the mouth, or an altered taste or smell.

A burning sensation in the mouth can be a symptom of another disease when local or systemic factors are found to be implicated, and this is not considered to be burning mouth syndrome, which is a syndrome of medically unexplained symptoms. The International Association for the Study of Pain defines burning mouth syndrome as "a distinctive nosological entity characterized by unremitting oral burning or similar pain in the absence of detectable mucosal changes", and "burning pain in the tongue or other oral mucous membranes", and the International Headache Society defines it as "an intra-oral burning sensation for which no medical or dental cause can be found".

Due to insufficient evidence it is unclear if effective treatments exist.

Angular cheilitis is a fairly non specific term which describes the presence of an inflammatory lesion in a particular anatomic site (i.e. the corner of the mouth). As there are different possible causes and contributing factors from one person to the next, the appearance of the lesion is somewhat variable. The lesions are more commonly symmetrically present on both sides of the mouth, but sometimes only one side may be affected. In some cases, the lesion may be confined to the mucosa of the lips, and in other cases the lesion may extend past the vermilion border (the edge where the lining on the lips becomes the skin on the face) onto the facial skin. Initially, the corners of the mouth develop a gray-white thickening and adjacent erythema (redness). Later, the usual appearance is a roughly triangular area of erythema, edema (swelling) and breakdown of skin at either corner of the mouth. The mucosa of the lip may become fissured (cracked), crusted, ulcerated or atrophied. There is not usually any bleeding. Where the skin is involved, there may be radiating rhagades (linear fissures) from the corner of the mouth. Infrequently, the dermatitis (which may resemble eczema) can extend from the corner of the mouth to the skin of the cheek or chin. If "Staphylococcus aureus" is involved, the lesion may show golden yellow crusts. In chronic angular cheilitis, there may be suppuration (pus formation), exfoliation (scaling) and formation of granulation tissue.

Sometimes contributing factors can be readily seen, such as loss of lower face height from poorly made or worn dentures, which results in mandibular overclosure ("collapse of jaws"). If there is a nutritional deficiency underlying the condition, various other signs and symptoms such as glossitis (swollen tongue) may be present. In people with angular cheilitis who wear dentures, often there may be erythematous mucosa underneath the denture (normally the upper denture), an appearance consistent with denture-related stomatitis. Typically the lesions give symptoms of soreness, pain, pruritus (itching) or burning or a raw feeling.

People with tree nut allergy are seldom allergic to just one type of nut, and are therefore usually advised to avoid all tree nuts, even though an individual may not be allergic to the nuts of all species of trees.

Someone allergic to walnuts or pecans may not have an allergy to cashews or pistachios, because the two groups are only distantly related and do not necessarily share related allergenic proteins. The severity of the allergy varies from person to person, and exposure can increase sensitization. For those with a milder form of the allergy, a reaction which makes the throat feel like cotton may occur. Subjects allergic to tree nut can experience asthma, skin rashes, itchy throat, swollen eyes. The most severe reaction can lead to anaphylaxis and sensitive subjects may need to carry with them at all times disposable adrenaline injectors prescribed by their GP. Less severe reaction can be dealt with by assuming antihistamines tablet. The raw nut protein usually causes a more severe reaction than the oil, and extra roasting or processing can reduce the allergic reaction. Those diagnosed with anaphylaxis will have a more immediate mast cell reaction and be required to avoid all exposure to any allergen-containing products or byproducts, regardless of processing, as they are prone to even greater sensitivity. An allergy test or food challenge may be performed at an allergy clinic to determine the exact allergens. New immunotherapy treatments are being developed for tree nut allergy.

This allergy tends to be lifelong; recent studies have shown that only about 9% of children outgrow their tree nut allergy.

Hazelnut has been used as a model tree nut in the study of tree nut allergies.

Angular cheilitis (AC), is inflammation of one or both corners of the mouth. Often the corners are red with skin breakdown and crusting. It can also be itchy or painful. The condition can last for days to years. Angular cheilitis is a type of cheilitis (inflammation of the lips).

Angular cheilitis can be caused by infection, irritation, or allergies. Infections include by fungi such as "Candida albicans" and bacteria such as "Staph. aureus". Irritants include poorly fitting dentures, licking the lips or drooling, mouth breathing resulting in a dry mouth, sun exposure, overclosure of the mouth, smoking, and minor trauma. Allergies may include to substances like toothpaste, makeup, and food. Often a number of factors are involved. Other factors may include poor nutrition or poor immune function. Diagnosis may be helped by testing for infections and patch testing for allergies.

Treatment for angular cheilitis is typically based on the underlying causes along with the use of a barrier cream. Frequently an antifungal and antibacterial cream is also tried. Angular cheilitis is a fairly common problem, with estimates that it affects 0.7% of the population. It occurs most often in the 30s to 60s, although is also relatively common in children. In the developing world, iron and vitamin deficiencies are a common cause.

Medications given for halogenoderma may include topical and systemic corticosteroids, diuretics, and cyclosporine.

Halogenodermas are skin eruptions that result after exposure to halogen-containing drugs or substances. This may last several weeks after drug use is discontinued. This is because of the slow elimination rate of iodides and bromides. Fluoroderma is a particular type of halogenoderma which is caused by fluoride. Fluoride is present in oral hygiene products such as toothpastes and mouth washes, hence this type of acne is seen mostly around the mouth and jawline. Acute fluoroderma has been observed in patients exposed to anaesthetics containing fluoride such as sevoflurane.

Dental plaque is a biofilm or mass of bacteria that grows on surfaces within the mouth. It is a sticky colorless deposit at first, but when it forms tartar, it is often brown or pale yellow. It is commonly found between the teeth, on the front of teeth, behind teeth, on chewing surfaces, along the gumline, or below the gumline cervical margins. Dental plaque is also known as microbial plaque, oral biofilm, dental biofilm, dental plaque biofilm or bacterial plaque biofilm.

Progression and build-up of dental plaque can give rise to tooth decay – the localised destruction of the tissues of the tooth by acid produced from the bacterial degradation of fermentable sugar – and periodontal problems such as gingivitis and periodontitis; hence it is important to disrupt the mass of bacteria and remove it. Plaque control and removal can be achieved with correct daily or twice-daily tooth brushing and use of interdental aids such as dental floss and interdental brushes.

Oral hygiene is important as dental biofilms may become acidic causing demineralization of the teeth (also known as dental caries) or harden into dental calculus (also known as tartar). Calculus cannot be removed through tooth brushing or with interdental aids, but only through professional cleaning.

Needle cast diseases in general are somewhat difficult to diagnose simply because their symptoms are similar to low pH, poor nutrition, fertilizer or chemical burn, and even root rots. Correct diagnosis requires microscopic examination of the size and shape of the fungal producing ascospores. Unfortunately these fungal spores are produced quite infrequently; after the disease infects needles, it will not produce symptoms or additional spores until the following year. In addition, "Cyclaneusma" may not be the only fungus present on the diseased needles. Saprophytic fungi live on dead tissue and may therefore continue to worsen the infection on needles after they have fallen. Saprophytes will also be present if the needles were killed by fertilizer burn or root rots. Due to these obstacles, it is important to examine the spores directly after infection (while spores are being produced) in order to ensure that "Cyclaneusma" is indeed the pine’s cause of death.

Brachygnathism or colloquially Parrot Mouth, is the uneven alignment of the upper and lower teeth in horses. In serious cases, the upper teeth protrude beyond the lower teeth. Problem with parrot mouth occur if the molars at the back of the mouth are also uneven, resulting in large hooks forming on the upper molars and the rear of the lower back molars. Horses with parrot mouth often require dental treatment at least every six months to remove the hooks and maintain alignment.

The equivalent conditions in humans are termed retrognathism or prognathism depending on whether the lower jaw is too far back or too far forward respectively.