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Oral Pathology - Level 2

From the Jaws of Defeat

Learn about three common oral diseases in dogs, their symptoms, causes and treatment methods.
By Eve Adamson

You feed your dog, groom him, train him and take him to the veterinarian, but if you aren’t also looking into his mouth every day, you are neglecting an important part of his health. However, unless you know what to look for, you may miss the obvious signs of dental disease, as well as the optimal window for treatment.

Sink your teeth into this lesson on three common oral diseases in dogs and you’ll know exactly what to look for. “Brushing your dog’s teeth and examining his mouth every day is the best way to prevent dental disease and to catch problems early, when they are still treatable,” says Dale Kressin, D.V.M., FAVD, a Diplomate of the American Veterinary Dental College and a veterinary dentist at Animal Dentistry and Oral Surgery Specialists LLC.

Periodontal Disease

What is it?
Periodontal disease is the most common disease in pets, according to Kressin. It affects the supporting structures of the teeth, called the periodontium, which include four separate components:

  • Gingiva (gums)
  • Periodontal ligaments, which are the shock absorbers for the teeth
  • Alveolar bone, which forms the socket that holds the teeth
  • Cementum, or covering of the teeth

Periodontal disease affects any or all of these structures and occurs in four stages. Stage 1, gingivitis, is characterized by inflammation of gum tissue, but no actual damage to the supporting structures. “Stage 1 is totally reversible,” Kressin says. Stages 2, 3, and 4, called periodontitis, are characterized by progressive, irreversible damage to the periodontium.

Stage 2 is defined by up to 25-percent loss of tooth attachment to the supporting structures. Stage 3 involves 25- to 50-percent loss of tooth attachment. Stage 4 indicates 50 percent or more loss of tooth attachment. The degree of severity must be determined through oral examination, oral probing under anesthesia and dental X-ray. “An accurate diagnosis of periodontal disease and its stage or severity is essential prior to treatment, as the stage of the disease determines the appropriate treatment,” Kressin says.

Periodontal disease is caused by the destructive presence of plaque bacteria in the mouth. Whether or not a particular dog will develop periodontal disease may be related to the dog’s age, diet, mouth size, tooth shape, jaw shape, immune status, general health, genetic predisposition, breed, chewing habits, natural bacterial flora of the mouth and, most significantly, lack of good oral hygiene. Without good oral hygiene, which systematically removes bacteria from the teeth, the bacteria can cause infection.

Plaque bacteria are actually a composite of glycoproteins from saliva and extra-cellular substances such as polysaccharides that adhere to the tooth. When plaque bacteria remain on the teeth for extended periods, it causes infection to the periodontium, instigating periodontal disease. Plaque bacteria begin to form in the mouth within hours after its removal, so daily brushing is the best way to prevent periodontal disease, according to Kressin.


  • Redness and inflammation of the gums.
  • Plaque and calculus (tartar) on the teeth.
  • Bad breath (“dog breath” is not normal and often a sign of periodontal disease, Kressin says).
  • Bleeding gums, especially during brushing or upon oral exam with a dental probe.
  • Receding gums, exposed tooth roots.
  • Sores in the mouth.
  • Discharge from gums or from between teeth.
  • Loose teeth or tooth loss.
  • Signs of pain including refusal to eat, dropping food, or signs that a dog is not chewing on one side, such as an accumulation of tartar and debris on the side of the mouth the dog isn’t using.

Treatment for Stage 1 periodontal disease (gingivitis) is a professional veterinary dental cleaning under anesthesia along with regular brushing at home. Small dogs tend to require at least yearly cleanings. Some larger dogs can get by with cleanings every other year. For more advanced periodontal disease (periodontitis) in which tissue and/or bone destruction has already occurred, treatment may involve varying degrees of oral reconstructive surgery with or without tooth extraction. 

Endodontic Disease

What is it?
Endodontic disease is an infection of the tooth pulp, or the inside of the tooth. When the tooth pulp is initially exposed to bacteria, inflammation develops, then infection and, finally, death of the tooth. Even when the tooth dies, endodontic disease can be dangerous for pets. “The bacteria remains in the tooth and from there it can travel out to the surrounding tooth structure, causing periodontal disease, and can even go into the bloodstream, causing systemic health problems that could affect major organ systems,” Kressin says. 

The most common cause of endodontic disease is tooth fracture. When a tooth breaks, the pulp is exposed and bacteria from the mouth can enter into the pulp. Even a chipped or abraded tooth (for example, in a dog that chews on rocks and wears away the tooth enamel) can lead to endodontic disease. “The tissue immediately below the enamel is called the dentin,” Kressin says. “The dentin has little tubules that connect with the pulp. If the enamel chips away, exposing the dentin, bacteria can enter the tooth through these tubules.” A less common cause of endodontic disease is advanced periodontitis. “Advanced periodontal disease can cause such severe destruction of the supporting structures of the tooth that infection can get down to the bottom of the tooth and into the apex, causing endodontic disease,” Kressin says. A cavity that penetrates the tooth enamel can also lead to endodontic disease. 


  • Broken or chipped tooth, especially when the pulp is exposed. Any tooth chip or fracture puts a dog at risk for endodontic disease and requires veterinary attention.
  • Discolored tooth (may be pink, purple, tan, brown or black).
  • Signs of pain, including refusal to eat.
  • Swelling or discharge around a tooth.
  • Pets may show no sign of endodontic disease until the tooth dies and begins to discolor.

Depending on the severity of the infection, treatment may involve extraction of the tooth, root canal therapy, or in the case of a broken tooth, a pulpotomy and direct pulp capping, involving removal of the exposed (and potentially infected) pulp and capping to seal the tooth and prevent further infection. Antibiotics are often necessary in addition to surgery, to get the infection under control.

Oral Tumor

What is it?
About 6 percent of tumors in pet dogs occur in the mouth, and about half of those tumors are malignant, or cancerous. Oral tumors may be small or large, obvious or obscured behind teeth, and typically appear as fleshy masses that may be pink, brown, blue, black or a combination of colors. Not all oral lumps are tumors, and not all tumors are cancerous. The most common type of cancerous or malignant oral tumor is oral melanoma, but there are many other types, such as fibrosarcomas and squamous cell carcinomas. 

A veterinarian should examine any oral lump, and if cancer is suspected, the lump should be biopsied to determine whether it is malignant, and if so, what type of cancer it is. A dental X-ray is essential in diagnosing any oral lump, to determine how much it may have spread to surrounding structures including bone. Because oral tumors tend to spread to the chest, a chest X-ray also may be needed. Some veterinarians also examine the tumor with advanced imaging, such as a CAT scan, for a more useful three-dimensional image that can aid in an accurate diagnosis. 

Lumps in the mouth are not always tumors. They can be caused by tooth root infections, abscesses related to trauma or periodontal disease, complications from oral surgery, cysts, or cancerous tumors. Oral cysts may be caused by embedded teeth. The cause of oral tumors is unknown, although some may have a genetic component. 


  • Fleshy masses or lumps in or around the teeth, gums, mouth or face. 
  • Facial swelling or deformity (although facial swelling is usually caused by something else, such as an infection).
  • Signs of pain, including refusal to eat, although many oral tumors are not painful.

If it is possible to remove an oral tumor (it has not spread too extensively and the pet is healthy enough to endure the surgery), a veterinary oncologist will probably recommend this treatment, with or without radiation and/or chemotherapy, as appropriate for the type of tumor. The tumor and surrounding tissue must be removed so no cancer cells remain, so the sooner an oral tumor is diagnosed, and the smaller it is, the easier it is to remove successfully. If a malignant oral tumor has metastasized (spread to other areas of the body), the tumor may still be operable. The veterinarian, often in conjunction with a veterinary oncologist, should offer options and prognosis so the dog’s owner can decide whether surgery is worthwhile. When benign (non-cancerous) tumors become uncomfortable for the pet, they may also be surgically removed. 

Eve Adamson has been writing about dogs and dog health for 14 years. She is a DOG FANCY contributing editor and the author of over 50 books, including “The Simple Guide to a Healthy Dog,” “Pets Gone Green,” and “Chowhound,” a dog treat cookbook.

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Give us your opinion Give us your opinion on Oral Pathology 201 Course

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Melissa   cheectowag, NY

6/24/2011 2:04:49 PM

I have found that the use of doggy "mouthwash" available in pet supply stores also helps. A few drops in the water really helps to keep the placque off. I had a 15 years old husky that had no doggy breath and only had 1 dental cleaning during her life. She dies with all her teeth accept 1 which has to be extracted after she cracked it on a rock.

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Gianna   Linden, NJ

6/7/2011 11:38:44 AM

This is very good information. My miniature Dachshund has very bad breath. She won't let me brush her teeth, but now after reading this I plan on taking her to the vet and somehow brushing her teeth. I love all the dog college courses, you can learn so much about caring for your dog!

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Kimmi   Sterling, OH

2/23/2011 6:43:46 PM

Very interesting!

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Mozart/Care   Ballston Spa, NY

2/19/2011 2:28:19 PM

Very informative!

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