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Cats Don’t Get Cavities? Get the Facts on Tooth Resorption

What cat owners believe is a cavity is something called tooth resorption, which might be linked to vitamin D intake. Here's what you can do.

Lisa Richman  |  Dec 29th 2014


Cats don’t get cavities. Did you know that? I didn’t. What pet owners often mistake for a cavity in a cat is something called tooth resorption. And guess what? No one really knows what causes it. Here’s the story of what my cat went through, and how I learned about this cat health issue.

Being a thrifty cat mom, when I heard in February that our vet offered a discount on dental cleanings, I signed up for three Fridays in a row, one cat per week. I ended up with a month of sheer misery — the cats’ and mine. It was largely spent going from cat to cat, administering post-oral surgery kitty morphine. Allie lost a back molar; Maxwell lost three. Poor Faraday took home the win for Most Teeth Lost, with four. Between three cats, that’s eight teeth.

Seriously, I asked my vet. What’s up with this? Is it something in the water?

Before talking about tooth resorption, it might help to know a little something about cats’ teeth. Imagine a bunch of concentric ovals. The outermost layer above the gums is the enamel. It’s very thin, but it’s the toughest part of the tooth. It also happens to be the hardest substance in the body — human or feline.

The next layer takes up the most room. It’s made from a bone-like material called dentin. Inside is a very soft substance: the pulp of the tooth. A lot goes on here. It’s the rich environment that feeds and nourishes the tooth, and it serves as the tooth’s nerve center. These are the tooth’s security and alarm systems, letting its host know when something’s wrong by sending signals of sensitivity or pain.

What is tooth resorption?

The illustration above is of a healthy tooth. The one below is Faraday’s. A big chunk of his tooth is just … gone. It was reabsorbed into the surrounding tissue. That’s where this condition differs from cavities. A cavity occurs when erosion or decay is present. Resorption is the process where a substance is absorbed back into its surroundings.

In the case of tooth resorption — or TR — the outer layers begin to be eaten away, absorbed into internal layers. In many cases, the roots reabsorb into the surrounding flesh until nothing remains. That was the case with poor Faraday. X-rays showed nothing but soft tissue, a tooth cap resting precariously at the gum line, the base of the tooth exposing all that soft pulp.

The tooth is irreparably damaged, and there is no option but to remove it. Removal can be a dicey process, too, as these teeth are often so compromised that they have become brittle and may shatter during extraction.

As resorption progresses and the nerve center is exposed, a cat can experience a lot of pain. Cats are notorious at hiding pain, so you might have to pay close attention to see this. Look for drooling, a preference for eating on one side of the mouth, or suddenly starting to swallow food whole. If your cat will let you, look at his teeth and see if you notice any red spots on the tooth, or -ÔÇô in Faraday’s case — gaping holes.

We can’t prevent tooth resorption just yet. To do that, we’d need to know its cause. We don’t, although a few studies suggest a culprit: diet. Specifically, the amount of Vitamin D in a cat’s diet.

Cats and vitamin D

I was surprised to learn that cats cannot absorb vitamin D through their skin, much to their chagrin — after all, they so love to sunbathe! That means they need to get their vitamin D from food, so it’s good that pet food manufacturers add it.

Yet a 2006 study found 41 percent of canned cat foods had over 30 times the amount of vitamin D recommended for cats, according to an article in dvm360.com. Since 2003, a few studies have found correlations between excessive vitamin D and cats suffering from tooth resorption. Another study recorded how vitamin D affected dental and gum tissue when large amounts of it were introduced. The changes recorded were very similar to those seen in tooth-resorption-damaged teeth.

But then a report from the Journal of Veterinary Dentistry found the inverse: Out of 64 cats studied, the ones with tooth resorption had much lower vitamin D serum levels than those without. All were fed dry cat food. No canned food was in this study. And it wasn’t dry food that was discovered in 2006 to have excessive levels of vitamin D — it was wet food.

So until a new study is commissioned that investigates tooth resorption in cats fed wet diets, all we have are conflicting studies and a lot of questions.

What should we do?

It’s incontrovertible that high levels of vitamin D pose a health risk to your pet. Low levels of vitamin D are equally dangerous. Most pet food labels list vitamin D as a supplement, but they don’t include the amount it contains. It doesn’t matter, since there’s no definitive decision on how much is good or bad.

Until the vitamin D debate is solved, there are a few things you can do if your cat has been diagnosed with tooth resorption:

  • Take your cat in for dental checkups twice a year instead of just at the annual wellness exam.
  • Some researchers believe that inflammation plays a role, so consider brushing to remove plaque, or rubbing an anti-inflammatory such as Ellagic fatty acid complex on the gums.

I hope veterinary medicine will identify the cause of tooth resorption in the near future, so we can work to prevent it. In the meantime, proactive dental hygiene, scheduling regular exams, and professional cleaning are our best defense.

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