The “endodontic system” is the hollow area inside a tooth that is filled with sensitive pulp tissue (blood vessels, nerves, and connective tissue), which allows the teeth to grow, mature and respond to stress. The blood supply and nerves enter the teeth through a collection of small holes in the tips of the roots (‘apical delta’) in dogs and cats.

Endodontic disease refers to damage to the dental pulp, commonly termed pulpitis. Depending on the severity of the insult, the pulpitis may be reversible or irreversible. Reversible pulpitis is usually caused by minor trauma, with the tooth surviving the insult. Irreversible pulpitis is a result of inflammation – the tissues swell, preventing blood from entering the root canal; the result is “death” of the tooth. The most common cause of irreversible pulpitis in veterinary patients is fracture of a tooth, exposing the pulp tissue to bacteria in the oral cavity. When this occurs, the inside of the tooth eventually fills with infected material that trickles through the openings in the tip of the root into the jaw. Since the bacteria have a secure hiding place inside the root canal, the body’s immune system is unable to clear up the infection, even with antibiotic treatment.

Fractured teeth are a very common occurrence in dogs and cats, resulting from external trauma (e.g. when a tooth is hit by a car or other hard object) or chewing on hard objects. The teeth most frequently broken are the canine (fang) teeth in the dog and the cat, and the upper fourth premolar teeth (the carnassial teeth – the large upper teeth in the back of the mouth) in dogs.

Anyone who has experienced endodontic pain in their own mouth can verify that this can be very painful. Unfortunately, our animal patients rarely show obvious signs of discomfort; pets tend to hide their pain, much as a wild animal attempts to avoid being singled out by a predator. The absence of obvious signs of pain encourages owners to be unaware of or ignore the problem, since “it doesn’t seem to bother the pet”. We now know that these animals are affected locally as well as systemically, and that ignoring the problem is not a good option. Many clients who felt confident that their pet was not bothered by a broken tooth relate that their pet acted “years younger” shortly after the endodontic problem had been correctly treated.

Although most fractured/infected teeth are not associated with swelling or drainage, sometimes the infection seeping out of the root tips will cause swelling or drainage through the skin or into the mouth. This most commonly occurs with a fracture of the large upper fourth premolar in dogs, which drains through the skin of the face below the eye. In cats, a draining tract may occasionally be seen below the eye. Although antibiotic treatment may temporally resolve the clinical signs, invariably the problem will reoccur if the offending tooth is not effectively treated.

A radiograph is an essential first step, to evaluate the bone and confirm that the root is intact. There are two options for dealing with a fractured tooth that has exposed the pulp chamber. Ignoring the problem is not a good choice.

One option is root canal therapy. This involves removal of the diseased pulpal tissue. The clean and disinfected root canal is then filled with an inert material to prevent future bacterial contamination. Tooth-colored restorations are then placed to seal the crown against further infection. Results of root canal treatment are excellent when the procedure is performed well.

However, without the right equipment, materials and training, it is easy to perform the procedure poorly. Following completion of a root canal procedure, a radiograph must always be taken to confirm that the canal has been completely filled.

A related procedure used in immature teeth is vital pulp therapy. This may be performed on recently fractured teeth in younger patients (under 18 months of age). This treatment can help keep the tooth alive, allowing it to become stronger subsequently by laying down new dentin internally. Most veterinary dentists rarely perform this procedure in older patients due to the higher risk of failure when compared to root canal therapy. Teeth treated with vital pulp therapy may require root canal treatment if the vital pulp therapy fails.

The only other option for treatment is extraction of the diseased tooth. For the large canine teeth in dogs and cats, and the large chewing (carnassial) teeth in dogs, the extraction procedure can be traumatic and painful due to the size of the roots in our animal patients. The root of the canine tooth is longer and wider than the crown (the part of the tooth you can see above the gums). Extraction of these teeth involves major oral surgery, comparable to removing impacted wisdom teeth in human patients. The patient also loses the function of the tooth, which can be very important in working dogs. Most veterinary dentists try to avoid extraction of fractured but otherwise healthy teeth.

A metal crown may be indicated following root canal treatment, depending on the extent of crown that is missing and the function of the dog.