Tooth Root Abscess in Cats

By Lorraine Hiscox DVM FAVD Dip. AVDC; Jan Bellows, DVM, Dipl. AVDC, ABVP

Abscessed root of a lower canine toothWhat is a tooth root abscess?

A tooth root abscess is a severe infection that develops around the root of a tooth usually occurring as a result of bacteria entering through a broken or traumatized tooth.

When does a tooth root abscess develop?

A tooth root abscess develops when bacteria enter the exposed root canal of the tooth.

The crown of a health tooth is covered by enamel. Enamel is essentially impervious, preventing bacteria from entering into the tooth. Beneath the enamel is a different dental hard tissue known as dentin. Dentin contains approximately 300-400,000 small openings (tubules) that communicate with the center of the tooth. In the center of the tooth is the pulp cavity which contains the soft tissue (blood vessels, nerves, and lymphatic tissue). The tissue in the pulp cavity is collectively referred to as the pulp. The pulp nurtures the normal tooth.

If the protective tooth enamel is chipped, thereby exposing the underlying dentin or the tooth is fractured more deeply exposing the pulp, bacteria can gain access to the center of the tooth. In cats, this most often occurs when the tooth breaks and exposes the tissues that lay beneath the enamel. A tooth root abscess may also develop in association with periodontal disease which is an infection of the tissues surrounding the tooth.

"If the protective tooth enamel is chipped exposing the pulp, bacteria can gain access to the center of the tooth."

Once infected with bacteria, the pulp tissue becomes inflamed (pulpitis) and eventually the tooth dies (pulp necrosis). Inflammatory products produced by the bacteria and dying pulp tissue leak out of the bottom of the root (root apex) and infection now contaminates the bone surrounding the root resulting in apical periodontitis. A persistent infection can result in an abscess (an accumulation of pus) that may leak directly into the oral cavity or may leak out onto the skin (beneath the chin if the affected root is in the lower jaw or onto the face if the affected root is that of an upper tooth). Pulpitis, apical periodontitis, and tooth root abscesses can be very painful.

A tooth root abscess may also occur secondary to periodontal disease. In this scenario, the infection does not travel down to the bone through the center of the tooth, but rather tracks along the outside of the tooth through the supportive tissues that surround the root.

 Slab fracture of the left upper fourth

What is the most common location for a tooth root abscess in cats?

Any tooth can fracture; however, the large upper and lower canine teeth, followed by the upper fourth premolars, are the most commonly fractured teeth. As a result, it is these teeth that are most likely to develop a tooth root abscess. The maxillary (upper) fourth premolars in conjunction with the lower (mandibular) first molars are known as the carnassial teeth. When it is one of these teeth that become infected, it is referred to as a carnassial tooth abscess.

When a tooth fractures, exposing the interior soft tissue (the pulp), the ensuing infection is severe and painful.

What is a slab fracture?

A slab fracture develops when a tooth breaks in such a way as to result in a loss of a “slab” of tooth structure. It occurs when the cat bites down on a hard object at just the right angle and with just the right force to break off a flake or slab of the tooth. This exposes the underlying sensitive dentin and sometimes even deeper, exposing the pulp cavity of the tooth where the nerve resides. The slab that breaks off may be a small chip or a large piece of the tooth.

Are there any obvious symptoms when a cat has a tooth root abscess?

Although humans know that abscessed teeth are very painful, cats with a tooth root abscess may not show any obvious outward signs of pain. Instead, your cat may be reluctant to chew on her toys or she might pull away when her head is touched. An observant owner may notice that their cat is only eating or chewing on one side of her mouth, or that she drops her food when chewing on the affected side.

"Your cat may be reluctant to chew on her toys or she might pull away when her head is touched."

Some cats will also have bad breath while others may paw at the affected side of their face or rub their face along the ground. Cat owners may assume their cat simply has an itch, but it could be the sign of an abscessed tooth.

If the abscessed tooth is the upper fourth premolar the outward signs are often mistaken for some other problem such as an eye infection or a puncture wound. This is because these tooth roots lie just below the eye, and when they become abscessed the infection quickly spreads to the surrounding tissues. The tissue below the eye will usually become swollen and inflamed just before the abscess ruptures. If you look inside the cat's mouth, there may be a swelling and redness on the oral soft tissue around the affected tooth.

How is a tooth root abscess diagnosed?

In some cases, such as when there is an obvious slab fracture or damage to a tooth that is accompanied by the presence of a discharge, the diagnosis of a tooth root abscess is simple and straightforward. However, intraoral dental radiographs (dental X-rays) are required to definitively diagnose a tooth root abscess. Your veterinarian may refer you to a veterinary dental specialist who can confirm the tooth root infection and to determine if other teeth are involved.

What is the treatment for a tooth root abscess?

A tooth root abscess is a very painful condition and needs to be treated as soon as possible. Antibiotics will be prescribed to control the infection and either an anti-inflammatory and/or pain relief medication will be prescribed as well. Although this medical treatment will deal with the symptoms, it will not treat the underlying tooth injury.

"A tooth root abscess is a very painful condition and needs to be treated as soon as possible."

There are only two options for treatment of the abscessed tooth. One option is a root canal treatment, (standard endodontic therapy) which can preserve the structure of the tooth. The other option is extraction.

The success of root canal therapy is dependent on the state of the surrounding tissues and the condition of the affected tooth. It is necessary that the tooth root in question be assessed clinically and via radiographs to determine if it is a good candidate for root canal treatment. The extent of trauma to the crown of the tooth, pre-existing infection (bone destruction around the root), along with the overall periodontal health of the tooth will impact whether a recommendation is made for root canal treatment or extraction. Root canal therapy should be rechecked with intraoral radiographs (requiring a brief general anesthetic) 3-6 months after the initial treatment and annually for the next couple of years.

Some general practitioners are comfortable performing a root canal treatment, but many veterinarians will refer these complex cases to a veterinary dental specialist (

     Fractured lower canine with nerve exposure    Root canal therapy to save the tooth

 Restored saved toothIf the abscessed tooth has extensive bone loss around its socket, or if there is significant damage to the crown of the tooth, your veterinarian may recommend extraction as the best treatment. Your veterinarian is in the best position to recommend the appropriate option for your cat, depending on the severity of the abscess and the degree of damage to the tooth and surrounding structures.

If the abscessed tooth is extracted, your veterinarian may prescribe antibiotics for a short period of time. Pain medication. will also be prescribed. Your cat may or may not require a change in diet during the post-operative recovery period. Once the gum tissue has healed, most cats can resume their regular diet and activity level.

All cats should have a dental examination performed by their veterinarian at least every six months. For a cat that has previously developed a tooth root abscess, your veterinarian may recommend more frequent dental examinations.

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