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* This is the Veterinary Version. *

Disorders of the Mouth in Dogs

By Dana G. Allen, DVM, MSc, DACVIM, Professor and Chair, Department of Clinical Studies, Ontario Veterinary College, University of Guelph ; Lisa E. Moore, DVM, DACVIM ; Carlton L. Gyles, DVM, PhD, Professor Emeritus, Department of Pathobiology, Ontario Veterinary College, University of Guelph ; Sharon Patton, MS, PhD, Professor of Parasitology, Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee ; Andrew S. Peregrine, BVMS, PhD, DVM, DEVPC, DACVM, Associate Professor, Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada ; Thomas W. Swerczek, DVM, PhD, Professor, Department of Veterinary Science, University of Kentucky ; Ben H. Colmery, DVM, DAVDC ; James G. Fox, DVM, MS, DACLAM, Professor and Director, Division of Comparative Medicine, Massachusetts Institute of Technology ; H. Carolien Rutgers, DVM, MS, DACVIM, DECVIM-CA, DSAM, MRCVS, Senior Lecturer, The Royal Veterinary College, University of London ; Jörg M. Steiner, DrMedVet, PhD, DACVIM, DECVIM-CA, AGAF, Associate Professor and Director, Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A & M University ; Sofie Muylle, DVM, PhD, Faculty of Veterinary Medicine, Department of Morphology, Ghent University ; Walter Ingwersen, DVM, DVSc, DACVIM, Specialist, Companion Animals, Boehringer Ingelheim (Canada) Ltd, Vetmedica ; Stanley I. Rubin, DVM, MS, DACVIM, Clinical Professor, Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois at Urbana-Champaign ; Sharon Campbell, DVM, MS, DACVIM, Manager, Pharmacovigilance Regulatory Affairs, Veterinary Medicine Research and Development, Pfizer Inc.

Also see professional content regarding mouth disorders.

The primary function of the mouth is to obtain and introduce food into the digestive tract. Some of its additional functions include communication and social interaction, grooming, protection, and heat regulation (particularly in dogs). Picking up food, chewing, and swallowing require a complex interaction of the muscles of the jaw, the teeth, the tongue, and the upper throat. When any of these functions becomes compromised through disease or trauma, malnutrition and dehydration may result. A complete oral examination should be a part of your animal’s physical examination, because oral diseases are most effectively treated with early diagnosis. Otherwise, many will remain hidden in the mouth and progress to an advanced stage.

Oral Inflammatory and Ulcerative Diseases

Gum disease (see Dental Disorders of Dogs : Gum Disease), is the most common oral problem in small animals. Other causes for oral inflammatory conditions include immune system disease, chemical agents, infections, trauma, metabolic disease, developmental abnormalities, burns, radiation treatment, and cancer. Infections that have been associated with oral inflammation include canine distemper virus and leptospirosis. Traumatic mouth inflammation may be seen after an animal tries to eat sharp plant material (such as plant awns) or fiberglass insulation. The houseplant Dieffenbachia may cause oral inflammation and sores if chewed. Chronic kidney failure can cause inflammation and sores in the mouth.

Signs vary with the cause and extent of inflammation. Loss of appetite may be seen. Bad breath and drooling are common with mouth inflammation, tongue inflammation, and sore throat. The saliva may be tinged with blood. The animal may paw at its mouth and, due to pain, resent or resist any attempt to examine its mouth. Lymph nodes in the region may be enlarged.

Chronic Ulcerative Stomatitis

Chronic ulcerative stomatitis involves inflammation of the mucous membranes of the mouth. Signs include severe gum inflammation, receding gums in several sites, and large sores on the mouth surface near the surfaces of large teeth. The problem commonly affects Greyhounds, but it has also been seen in Maltese, Miniature Schnauzers, Labrador Retrievers, and other breeds. The characteristic feature is the contact ulcer or sore that develops where the lip contacts the tooth surface, most commonly on the inner surface of the upper lip next to the upper canine teeth. These abnormalities have also been termed “kissing ulcers” because they are found where the lips “kiss” the teeth.

The cause of this disease is an immune system dysfunction that results in an excessive inflammatory response to dental plaque. For this reason, thorough plaque control through professional cleaning and excellent home oral hygiene (including tooth brushing) may resolve the problem. Supplemental antibacterial measures, such as topical chlorhexidine rinses or gels, may be prescribed by your veterinarian. In severe cases, topical anti-inflammatory preparations may provide comfort. Discomfort caused by the ulcers can make it difficult to brush your pet’s teeth and give oral medications. If discomfort is severe and you are unable to brush the teeth, extraction of the adjacent teeth may be necessary to remove the contact surfaces on which plaque accumulates. Although extraction may aid in control of the sores, it may not completely cure the problem, as plaque grows on all surfaces in the mouth and animals can continue to develop sores.

Lip Disorders

Lip fold dermatitis is a chronic skin inflammation that occurs in breeds with drooping upper lips and lower lip folds (such as spaniels, English Bulldogs, and Saint Bernards). These lips often accumulate moisture, causing inflammation to develop. The condition may be worsened when poor oral hygiene results in high salivary bacterial counts. The lower lip folds can become very bad-smelling, inflamed, uncomfortable, and swollen.

Treatment of lip fold dermatitis includes clipping the hair, cleaning the folds 1 to 2 times a day with benzoyl peroxide or a mild skin cleanser, and keeping the area dry. Your veterinarian may prescribe a daily application of a topical diaper rash cream. Surgical correction of deep lip folds is a more long-lasting remedy for severe cases.

Lip wounds, resulting from fights or chewing on sharp objects, are common and vary widely in severity. Thorns, grass awns, plant burrs, and fishhooks may embed in the lips and cause severe irritation or wounds. Irritants such as plastic or plant material may produce inflammation of the lips. Lip infections may develop. Wounds of the lips should be cleaned and sutured by your veterinarian, if necessary.

Direct extension of severe gum disease or inflammation inside the mouth can produce inflammation of the lips (cheilitis). Licking areas of bacterial dermatitis or infected wounds may spread the infection to the lips and lip folds. Inflammation of the lips also can be associated with parasitic infections, autoimmune skin diseases, and tumors.

Inflammation of the lips and lip folds can be short- or longterm. Animals may paw, scratch, or rub at their mouth or lip; have a foul odor on the breath; and occasionally salivate excessively or refuse to eat. With chronic infection of the lip margins or folds, the hair in these areas is discolored, moist, and matted with a thick, yellowish or brown, foul-smelling discharge overlying red skin that may have open sores. Sometimes the infection extends to another area of the body; this is easily diagnosed because of the lip inflammation that accompanies it.

Inflammation of the lips that is unrelated to lip folds usually resolves with minimal cleansing, appropriate antibiotics (if a bacterial infection is present), and specific treatment of the cause. Treatment of periodontal disease or mouth inflammation is necessary to prevent recurrence.

Infectious cheilitis that has spread from a location away from the mouth usually improves with treatment of the primary spot, but treatment of the lip area also is necessary. With severe infection, care includes clipping the hair from the infected area. The area will then be gently cleaned and dried. Antibiotics may be prescribed if the infection is severe or spreads to other locations.

Fungal Stomatitis

Fungal stomatitis is caused by overgrowth of the fungus Candida albicans. It is an uncommon cause of oral inflammation in dogs. The main sign is the appearance of creamy white flat areas (plaques) on the tongue or mucous membranes. It is usually thought to be associated with other oral diseases, longterm antibiotic treatment, or a suppressed immune system. In most cases, both the underlying disease and the fungal infection itself will be treated. Follow your veterinarian’s recommendations about diet carefully to support your pet’s recovery. Your veterinarian will also recommend a treatment program to control the fungus causing the problem. This is a critical phase of the treatment because the outlook is poor if the underlying disease cannot be adequately treated or controlled.

Trenchmouth

This relatively uncommon disease of dogs is characterized by severe inflammation of the gums (gingivitis), ulceration, and death of the tissue lining the mouth. The cause of this disease is unknown, but it has been suggested that normal mouth bacteria and other microorganisms may cause this disease after some predisposing factor either increases their levels or decreases the mouth’s resistance to infection. Other potential factors are stress, excess use of corticosteroids, and poor nutrition.

The disease first appears as reddening and swelling of the gum edges, which are painful, bleed easily, and may lead to receding gums. Extension to other areas of the inner mouth is common. In severe cases, this results in sores and exposed bone. Bad breath is severe, and the animal may be unwilling to eat due to pain. Excessive drooling may be present, and the saliva may be tinged with blood. The disease is diagnosed by excluding other possible causes.

Treatment generally consists of treatment for gum disease, professional cleaning of wounds, oral hygiene, antibiotics, and oral antiseptics.

Inflammation of the Tongue

Inflammation of the tongue is called glossitis. It may be due to infection, irritation, wounds, disease, or other causes such as electrical burns or insect stings. A thread, string, or other foreign object may get caught under the tongue. Glossitis can also occur in long-haired dogs that use the mouth and tongue in an attempt to remove plant burrs from their coats.

Drooling and a reluctance to eat are common signs, but the cause may go undiscovered unless the mouth is carefully examined. Gum disease may result in reddening, swelling, and occasionally sores on the edge of the tongue. There may be no inflammation of the upper surface of the tongue, but the lower surface may be painful, irritated, and cut by the foreign body. Porcupine quills, plant material, and other foreign materials may become embedded so deeply that they cannot be easily detected. Insect stings can cause sudden swelling of the tongue. Some animals have a tongue with a deep central groove, which often becomes filled with hairs that act as an irritant. In chronic cases of inflammation, a thick, brown, foul-smelling discharge (occasionally with bleeding) may be present. Frequently, the animal is reluctant to allow examination of its mouth.

Glossitis is treated by the veterinarian removing any foreign objects and any broken or diseased teeth. Infection may be treated with an appropriate antibiotic. Cleaning of the wounds and use of antiseptic mouthwashes are beneficial in some cases. A soft diet and intravenous fluids may be necessary. If the animal is weak and unable to eat well for a prolonged period, tube feeding may also be required. Sudden glossitis due to insect stings may require emergency treatment. If the glossitis is caused by another condition, the primary disease will also be treated. The tongue heals rapidly after irritation and infection have been eliminated.

Soft Tissue Trauma

Injuries to the cheeks or mouth are common in dogs, but usually respond well to treatment.

Cheek Biting

A wound along the side of the cheek may be caused by self-trauma when the tissue becomes trapped between the teeth during chewing. Surgical removal of the excess tissue prevents further injury.

Mouth Burns

Thermal (heat), chemical, or electrical burns involving the mouth are common in dogs. Your veterinarian will look for any injuries to other body systems. The injuries may be mild, with only temporary discomfort, or may be very destructive with loss of tissue and scar formation, followed by deformity or tissue loss. In some cases, these other injuries can be life-threatening. Sometimes puppies will be burned by chewing on an electrical cord. These animals often have a scar across the back of the tongue, outlining the path of the electrical cord. One or both lip corners may have a scar or wound, and the adjacent teeth may be discolored and eventually require a root canal treatment.

A dog with a burn to the mouth may hesitate to eat or drink, drool, or resent handling of its mouth or face. If tissue destruction is noticeable, sores and mouth inflammation may develop. Such wounds can easily become infected. If you observed the burn yourself, provide the details to your veterinarian. If the animal is seen by a veterinarian shortly after receiving a chemical burn to the mouth, he or she may be able to neutralize the chemical and/or flush it out with water. More commonly, the dog is seen by the veterinarian too long after exposure for neutralization to be effective.

If the animal has only a reddened mouth lining without tissue damage, it may require no treatment other than a soft or liquid diet until the soreness has healed. If tissue damage is extensive, the veterinarian may rinse the tissues with a chlor-hexidine solution and perform some cleansing to remove dead tissue and debris. Antibiotics may be prescribed to reduce the chance of infection.

Viral Warts and Papillomas

Viral warts are noncancerous growths caused by a virus. The mouth lining and corners of the lip are most frequently affected, but the roof and back of the mouth can also be involved. Viral warts are most common in young dogs and often appear suddenly, with rapid growth and spread. Signs are seen when the growths interfere with picking up food, chewing, or swallowing. Occasionally, if the growths are numerous, the dog may bite them when chewing, causing them to bleed and become infected. The warts may disappear spontaneously within a few weeks, and removal is generally not necessary. If necessary, a veterinarian can remove the warts surgically.

Papillomas look very much like viral warts, but they tend to grow more slowly and are less likely to be found in groups. They normally do not spread, and can be cured by surgical removal.

Oral Tumors

Tumors in the mouth and upper throat may be either benign (not cancerous) or malignant (cancerous).

Benign Tumors

The most common benign oral tumors in dogs are epulides. They may be seen in dogs of any age but are seen most frequently in dogs 6 years of age or older.

Epulides are firm masses involving the tissue of the gums. They arise from the ligament of the involved tooth. These masses generally occur alone, although multiple masses may be present. They can become quite extensive.

There are 2 general categories of epulides: peripheral odontogenic fibromas and canine peripheral ameloblastoma. Peripheral odontogenic fibromas may develop centers within the mass(es) that harden and turn into bone-like tissue. Canine peripheral ameloblastomas are benign but grow quickly. They routinely invade nearby tissues including bone. Because of their aggressive nature, these epulides should be surgically removed. Radiation treatment may help to minimize disfigurement if there are large tumors.

Due to the varied nature of epulides and other oral tumors, your veterinarian will want to biopsy the tumors prior to surgery. The results of the biopsy will guide the veterinarian in planning the surgery and any other required treatment.

A gingival fibroma is a benign growth on the gums that usually originates near the gum line. The growth is relatively insensitive and tough and is the color of the normal gum or more pale. The growth may become large enough to completely cover the surfaces of several teeth. Breeds with flat faces (brachycephalic breeds) may be more likely to develop this condition than other breeds. Gingival fibroma is most common in older dogs and usually causes no signs of illness. Hair, food, and debris may collect between the growth and the teeth and cause irritation and bad breath. Surgical removal is the most satisfactory treatment. After surgery, your pet may be prescribed a daily oral rinse to be used until the site is healed.

Malignant Tumors

In dogs, the most common types of malignant tumors are malignant melanoma, squamous cell carcinoma, and fibrosarcoma. The gums are affected most frequently. Signs vary depending on the location and extent of the tumor. Bad breath, reluctance to eat, and excessive drooling are common. If the back of the mouth and throat are involved, swallowing may be difficult. The tumors frequently ulcerate and bleed. The face may become swollen as the tumor enlarges and invades surrounding tissue. Lymph nodes near the tumor often become swollen before the tumor itself can be seen.

A tissue biopsy is usually required to confirm the diagnosis. If your veterinarian suspects that the tumor has spread, nearby lymph nodes and the lungs may be evaluated as well.

The treatment and outlook depend on the specific kind of tumor and whether it has spread. Malignant melanomas are highly invasive and spread readily; consequently, the outlook is guarded to poor. Surgical removal of the tumor can extend survival and may cure the condition; however, recurrence is common. Squamous cell carcinomas that do not involve the tonsils have a low rate of spread, and the outlook is good with aggressive surgery, radiation treatment, or both. Squamous cell carcinomas affecting the tonsils spread rapidly and have a poor outlook. Fibrosarcomas have a guarded outlook, and recurrence of tumor growth after surgery is common.

Salivary Disorders

Saliva moistens the mouth and helps begin the digestion of food. As with any other part of the body, there can be medical problems involving the glands that produce the saliva.

Excessive Salivation (Ptyalism or Sialosis)

Excessive salivation has 2 main causes: either the animal is producing too much saliva (a condition called ptyalism or sialosis), or the animal cannot effectively swallow the saliva that is produced. In either situation, the animal drools. There are a number of underlying causes for this condition (seeBox). The most serious of these is rabies, so your veterinarian will attempt to exclude that first. The underlying cause may be within or near the mouth, or it can be a sign of a more general condition. Whatever the cause, it will have to be determined and treated to control the condition. Short-term moist inflammation of the lips and face may develop if the skin is not kept as dry as possible. Cleansing with an antiseptic solution may be recommended.

Salivary Mucocele

In a salivary mucocele, saliva accumulates under the skin after damage to the salivary duct or gland. This is the most common salivary gland disorder of dogs. While any of the salivary glands may be affected, those under the tongue and in the jaw are involved most commonly. Usually, the cause is not determined.

The signs depend on the site of saliva accumulation. The first sign noticed may be a nonpainful, slowly enlarging mass, frequently in the neck. A mucocele under the tongue may not be seen until it is traumatized and bleeds. A pharyngeal (throat) mucocele may obstruct the airways and result in difficulty breathing. Pain or fever may occur if the mucocele becomes infected. A veterinarian can distinguish the mucocele from abscesses, tumors, and other types of cysts by using a needle to draw a sample of fluid from inside the mucocele.

Surgery is often recommended to remove the damaged salivary gland and duct. Mucoceles in the neck or under the tongue can be managed with periodic drainage if surgery is not an option. Complete gland and duct removal is often recommended for mucoceles in the throat to avoid the possibility of future life-threatening airway obstruction. Your veterinarian will consider your pet’s specific condition when making a treatment recommendation.

Salivary Fistula

Fistulas are abnormal paths or openings between 2 organs in the body or from an organ inside the body to the body surface. Fistulas involving the salivary glands in dogs and cats are rare. When they do occur, the cause may be an injury to the salivary glands in the lower jaw, the cheeks or face, or under the tongue. Other causes include bite wounds, abscess drainage, or the opening of a closed surgical incision.

Your veterinarian will want to be sure to correctly identify the fistula before recommending treatment. Draining sinuses should be eliminated as a source of the problem. If a fistula is the problem, surgery is often required. Tying off the involved salivary duct usually resolves the problem, although the associated gland may need to be removed.

Salivary Gland Tumors

Salivary gland tumors are rare in dogs. Most are seen in dogs that are more than 10 years old. Poodles and spaniel breeds may be predisposed. Most salivary gland tumors are malignant, with carcinomas and adenocarcinomas the most common. Spread to nearby lymph nodes and the lungs is common. Tumors removed by surgery alone tend to recur, so radiation treatment, with or without surgery, is often recommended.

Inflammation of the Salivary Glands

Inflammation of the salivary glands is rarely a problem in dogs. When it is found, it is frequently an incidental finding in addition to another disease or condition. Salivary gland infections may be caused by trauma (often from bites or other penetrating wounds) or from generalized infections such as rabies, distemper, and the virus that causes mumps in humans.

Signs of inflamed salivary glands include fever, depression, and painful, swollen salivary glands. Occasionally, an abscessed gland discharges pus into the surrounding tissue or the mouth. Rupture through the skin may cause a salivary fistula to form.

Mild inflammation may require no treatment. Recovery is often rapid and complete. If there are abscesses, these are normally drained and antibiotics given. If recovery is not complete within a few days, or if the infection recurs, your veterinarian will want to do laboratory tests on a tissue sample and a biopsy. Occasionally, surgical removal of the infected salivary gland is required.

Dry Mouth (Xerostomia)

Xerostomia is a decreased secretion of saliva that causes a dry mouth. It can cause significant discomfort and difficulty with eating. Historically, this condition is uncommon in dogs and cats, but is very common in humans who have damaged salivary glands following radiation treatment for tumors of the head and neck. As radiation treatment is used more commonly in veterinary medicine, this condition may become more frequent in pets. Decreased salivary secretion may also result from use of certain drugs, extreme dehydration, fever, anesthesia, or disease of the salivary gland. Finding and treating the underlying cause is important in controlling xerostomia. Specially formulated mouthwashes can often help relieve the discomfort that results from this condition. Fluids may be administered to correct dehydration, if present. If the condition is immune related, appropriate immunosuppressive treatment may be prescribed.

For More Information

Also see professional content regarding mouth disorders.

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* This is the Veterinary Version. *