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Ask a Vet: What Causes a Dog’s Tooth to Suddenly Turn Purple?

Teeth turn purple most frequently due to blunt-force trauma, and affected dogs need immediate treatment to prevent infection and bone loss.

Dr. Eric Barchas  |  Aug 25th 2015


If your dog, like mine, enjoys fetching and retrieving, I have a recommendation: Buy a Chuckit. What a genius invention — there is no need to get your hand slimy with dog drool, and the device allows for superhuman throwing distances. Heck, with a Chuckit you don’t even need to bend over to pick up the ball. When used in appropriate circumstances, a Chuckit is a very good thing indeed.  (Note: I have never received a penny of money from the makers of the Chuckit.)

Dr. Eric Barchas. (Photo by Liz Acosta)

Dr. Eric Barchas. (Photo by Liz Acosta)

When it comes to fetch, there is another invention that is purely a bad idea. Although it allows for even longer distances than a Chuckit, disasters are common when it is used. I am referring to the baseball bat.

The riskiness of swinging a baseball bat when playing fetch seems obvious to me, but maybe that’s because I’m the one who has to deal with the fallout. Here’s how it plays out: The owner usually has a long history of using a baseball bat to drive the fetch ball across the field. Things always have gone fine. But a time inevitably comes when the dog simply can’t control himself and feels an insuperable desire to grab the ball just before the bat strikes it. The owner then clocks his dog in the face with the bat.

Sometimes the damage done to the dog is obvious. I have seen many fractured (broken) teeth result from baseball bat fetch accidents. Most people know to seek veterinary attention when there’s a bloody sharp stump where a tooth used to be.

But sometimes the dog appears to have escaped without injury. There is no blood and the dog shakes off the pain and wants to keep fetching.

Dog with healthy teeth by Shutterstock.

Dog with healthy teeth by Shutterstock.

And then, later, one of the dog’s teeth changes color — it suddenly becomes purple. The tooth is just bruised, right? No big deal, right?

Wrong.

Teeth suddenly turn purple most frequently as a result of concussive (also known as blunt force) trauma. Baseball bat fetch accidents are common causes of this, but any strong blow to a tooth can result in concussive trauma.

Teeth consist of live cells with blood and nerves (called the pulp) surrounded by a hard shell. When a tooth suffers concussive trauma, blood and inflammatory cells flow into the pulp in an abnormal fashion. This leads to swelling. Under normal circumstances, swelling needn’t be very dangerous. Swelling in a muscle or joint may be painful, but usually the tissue can recover.

Unfortunately, teeth are different. The hard shell restricts the pulp’s ability to expand as it swells. Instead, pressure builds up. That pressure kills the pulp. After the pulp dies, blood cells break down and turn the tooth purple (although sometimes it starts off pink, then turns purple).

Dog with rotten teeth by Shutterstock.

Dog with rotten teeth by Shutterstock.

In other words, a suddenly discolored tooth usually is in fact a dead tooth. This is especially true in mature individuals (young dogs may rarely have pulp tissues that can survive the swelling).

What is the harm of having a dead tooth in the mouth? Infection is a major risk. The oral cavity is loaded with bacteria, and in healthy teeth the blood flowing through the pulp helps prevent the interior structures from becoming infected. In a dead tooth, the pulp is a sitting duck.

Once bacteria find their way into the pulp, the infection will spread toward the base of the tooth and then into the bone. The result can be bone loss, severe pain, and a dental abscess.

In certain rare instances, young dogs’ teeth may recover from concussive trauma. However, these instances are the exception rather than the rule. In general, and almost always in mature dogs, suddenly discolored teeth need treatment. It is best to treat them before the dog suffers significant consequences from devitalization of the tooth.

There are two treatments for devitalized teeth: They may be extracted (pulled) or a root canal can be performed. Almost any vet can perform an extraction (although pulling a young, recently devitalized tooth from a large dog’s mouth will cause most of us to work up a sweat). Root canals generally require a specialist in veterinary dentistry.

Root canals in dogs are similar to root canals in people, with one exception: Veterinary dentists have the decency to use general anesthesia. Once the dog is anesthetized, a hole is drilled through the hard structures of the tooth so that the dead pulp material can be cleaned out. The hollow pulp area is then filled with a synthetic material that fills the space and prevents infection, and the hole is sealed.

As I said, root canals usually are performed by specialists. And that’s not a bad thing, especially in young dogs who have some slight chance of their teeth recovering from concussive trauma. A specialist in dentistry will be able to confirm the need for treatment in such young dogs.

Read more from Dr. Barchas:

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