Structure and Function of the Tongue, Teeth and Mouth in Dogs
Disorders of the tongue may occur as isolated conditions, or may be involved with other disorders of the mouth. When the tongue is diseased, the animal may be reluctant to eat, may show abnormal chewing movements, may drool excessively, and have a foul odor or bloody discharge from the mouth.
What Are Some Diseases of the Tongue, Teeth and Mouth?
Glossitis is inflammation of the tongue. It may occur alone, or be associated with a generalized inflammation of the soft tissues of the mouth (stomatitis), inflammation of the gums (gingivitis), or of the lips (cheilitis). Causes of glossitis and stomatitis in the dog include the ingestion of foreign bodies (e.g. needles, fish hooks, tacks), exposure to chemicals and caustic agents, and irritating plants. Infectious diseases, particularly bacteria, the viruses that cause upper respiratory infections (e.g. adenovirus, distemper virus), and fungal agents (e.g. candidiasis, blastomycosis) can cause inflammation and ulceration of the tongue. Glossitis and stomatitis in the dog may also occur as a component of immune-mediated diseases, metabolic diseases, nutritional disorders, poisoning with certain toxins.
Ulcerations can develop on the tongue in association with systemic diseases such as kidney failure and certain cancers of the body. Ulcerations can also occur with a peculiar disease of dogs called eosinophilic granuloma or eosinophilic stomatitis. Collagen degeneration and the infiltration of white blood cells called eosinophils lead to ulceration and growths on the tongue and in other areas of the mouth, especially in the Siberian husky and Cavalier King Charles spaniel. The cause of this disease is not entirely understood.
Tumors or neoplasia may also occur on the tongue. The most tumors of the tongue in dogs are malignant, and include melanomas, squamous cell carcinomas, and fibrosarcoma. Oral papillomatosis is a contagious disease of young dogs caused by the papillomavirus. The virus causes cauliflower-type warts to develop all over the surfaces of the oral cavity. Most of these warts regress over several weeks on their own.
Trauma may also occur to the tongue. Injuries may include burns, lacerations, puncture wounds, and bite wounds.
A number of dental diseases occur in the dog. Such diseases may involve only the tooth, only the gums, or the supporting tissues of the teeth. Signs associated with dental disease include a foul odor to the breath (halitosis), difficulty chewing, pain upon chewing, discoloration of the teeth or gums, discharge or bleeding from the gums or mouth, and deformity of the teeth.
Abnormal numbers of teeth and retained deciduous may occur. Brachycephalic dogs with very short, blunt faces may have fewer teeth and shorter jaws that other dogs. Retained deciduous teeth are baby teeth that fail to fall out on their own. Any baby tooth that persists beyond six months of age is considered abnormal.
Abnormal bite may occur in dogs. If the upper and lower teeth to do line up properly, the condition is called a malocclusion. Sometimes the upper teeth hang out further in the front of the mouth than the bottom teeth, and sometimes the opposite occurs. Abnormal bites may lead to abnormal wearing of the teeth, chronic trauma to gums, and periodontal disease.
Periodontal disease is the development of plaque or tartar on the teeth, with secondary inflammation of the gums (gingivitis) and other supporting structures (periodontitis). Dental plaque is a yellow/gray/green substance that coats the surface of the tooth. It is composed of bacteria, proteins from saliva, and various other substances. Plaque is a major problem for animals because they do not routinely brush their teeth. Untreated plaque leads to infections around the teeth and potentially the loss of affected teeth.
Tooth root abscesses can occur in any tooth, but are usually associated with the premolar or molar teeth. They occur more often in upper teeth, than in lower teeth. They are characterized by the accumulation of pus around the root of the tooth. When upper teeth are involved swelling may occur on the face, just beneath the eye. If the abscess ruptures to the outside, a small draining hole may be seen on the face.
Trauma to the teeth is common in some animals. Some teeth become broken or cracked. Other teeth wear down over years of continuous use. Abrasions may also occur from chewing sharp objects. Clinical signs associated with dental trauma vary, depending upon whether the pulp cavity is exposed. Exposure of the pulp cavity is often painful.
Tumors near the teeth may develop from the supporting or surrounding tissues. An epulis is a benign growth than arises from periodontal tissue. It appears as a pink mass arising from the gums that can go so large as to cover one or more teeth. Ameloblastoma and odontoclastic tumors may also develop near the teeth.
The most common disorders of the mouth include stomatitis and tumors. Disorders of the salivary glands also affect the mouth. Clinical signs associated with these conditions including difficulty eating, reluctance or refusal to eat, halitosis, drooling, bleeding from the mouth, retching or gagging, pawing at the face, rubbing the face, fever and lethargy, and sometimes nasal discharge.
Stomatitis is an inflammation of the oral mucosa (lining of the mouth) and other soft tissues of the mouth. It has many potential causes, including all the causes of glossitis outlined above. Bacterial (e.g. spirochetes), viral (e.g. canine adenovirus, canine distemper virus), and fungal infections may cause stomatitis. Some bacteria that are normal residents of the mouth may take advantage of inflammation in the mouth to create significant infections.
Tumors of the mouth are often malignant in dogs and usually involve the soft tissues of the mouth. Tumors of the bones of the mouth are also possible, but occur less often. Examples include the malignant melanoma, squamous cell carcinoma, fibrosarcoma, and osteosarcoma.
A ranula is a swelling that develops under the tongue from the formation of a cyst of the sublingual salivary gland. The swelling may become large and inflamed, causing the tongue to be pushed upwards or to the side. The dog may have difficulty eating, may drool or exhibit excessive licking, and may act painful when the mouth is opened or manipulated. Cysts may also develop from other salivary glands and impinge upon the structures of the mouth.