Guest post by Dr. Karen Becker

When a kitty has oral disease, it generally has one of four causes:

  • Periodontal (gum) disease
  • Oral cancer (especially squamous cell carcinoma)
  • Feline stomatitis (an autoimmune disorder that causes painful inflammation of the mouth, throat or pharynx)
  • Tooth resorption

Tooth resorption is also referred to as cervical line lesions, resorptive lesions, feline odontoclastic resorptive lesions (FORLs), and (inaccurately) cavities. Of the four major feline oral diseases, tooth resorption is the most common. Estimates are the condition affects between about 30 to 40 percent of healthy adult cats, and from 60 to 80 percent of kitties who visit the vet for treatment of dental disease.

Feline tooth resorption was documented as early as the 1920’s, but it has increased significantly in domestic cats since the 1960’s. This timing would seem to point to the involvement of feeding, vaccination and /or neutering practices in the development of the disease. Purebred kitties, especially Persians and Siamese, may be more prone to the condition than other cats.

Tooth Resorption

Resorption is the process by which a structure loses substance and is eventually remodeled. Tooth resorption is the gradual destruction of a tooth or teeth caused by cells called odontoclasts. Tooth resorption usually starts on the outside of a tooth at the gum line. The condition is most common in premolars in the lower jaw, but can occur in any tooth.

If the resorption is obvious, it often looks as though gum tissue is growing over or into the tooth. It can also appear there is a hole in the tooth, which is why the condition is sometimes referred to as a cavity. In fact, cavities are extremely rare in companion animals, especially cats. Less visible resorptions can be found using magnification devices and lighting once the cat is anesthetized and immobile. But tooth resorption under the gum line must be diagnosed via dental x-rays.

Tooth resorption is a progressive disease which typically first erodes the cementum, or surface layer of the root, and the dentin, which is the hard tissue just below the enamel of the tooth. It then moves into the center of the tooth and the pulp, which is comprised of living connective tissue and cells. The resorption process continues into the fluid-filled dentinal tubules, tiny channels that spread outward through the dentin to the cementum. Finally, the enamel is resorbed, which can cause the tooth to fracture and/or remodel into a lump on the gum line. Resorbed cementum and dentin is replaced with hard, bone-like tissue.


As you might guess, feline tooth resorption is a painful condition. However, many cats show no obvious signs of pain unless and until a lesion is actually touched. Sometimes an affected cat will drool, have bleeding from the mouth, or difficulty eating. Occasionally there can also be vomiting of unchewed food, behavior changes and bad breath. But it is most often up to an observant pet owner or a veterinarian to diagnose tooth resorption in a kitty.

Stages of Tooth Resorption

There are five stages of tooth resorption. These are:

  • Stage 1 – Mild dental hard tissue loss, either cementum alone or cementum and enamel. In this stage of the disease, a defect in the tooth’s enamel is all that is usually noted. There is little to no sensitivity because the resorption has not yet reached the dentin.
  • Stage 2 – Moderate dental hard tissue loss including cementum or cementum and enamel, and loss of dentin that has not yet reached the pulp cavity.
  • Stage 3 – Deep dental hard tissue loss including cementum or cementum and enamel, and loss of dentin that extends to the pulp chamber. At this third stage of disease, most of the tooth is still viable.
  • Stage 4 – Extensive dental hard tissue loss and most of the tooth has lost its integrity. A significant amount of the tooth’s hard structure has been destroyed. Stage 4 has three sub-categories: 4a (crown and root of tooth are equally affected), 4b (crown is more severely affected than the root), and 4c (root is more severely affected than the crown).
  • Stage 5 – Only remnants of the tooth remain, covered by gum tissue. The majority of the tooth has been resorbed, leaving only a raised area on the gum.

Treatment of Feline Tooth Resorption

Extraction of a tooth undergoing resorption is the only treatment for the condition (unless the resorption has reached stage 5 and no inflammation is present). Extraction can be a tricky procedure to perform because affected teeth are usually quite fragile and often fracture and splinter during removal. X-rays should be taken to visualize fractured tooth fragments. The entire tooth and all fragments must be removed to prevent infection or other problems. Many kitties with tooth resorption also have feline stomatitis. In these pets, it is extremely important to remove all remnants of the tooth structure to prevent further immune system stimulation and painful oral inflammation.

Not every veterinary practice is equipped to deal with tooth resorptions. Dental x-ray and adequate surgical magnification equipment is necessary, as is proper training. If your pet is diagnosed with tooth resorption, you should insure your vet’s office is properly equipped and staffed to treat the disease. If not, you should request a referral to a specialist.


The exact cause of feline tooth resorption is still a mystery. And once a tooth resorption has been identified in your cat’s mouth, unfortunately, it’s very common for additional teeth to suffer the same fate. If your kitty has been diagnosed with tooth resorption, I recommend twice yearly dental checkups to screen for additional lesions. I also recommend you do regular at-home wellness exams, paying special attention to your cat’s teeth and gums.

A study published several years ago in the Journal of the American Veterinary Medical Association on the prevalence and risk factors for feline tooth resorption reported the following results:

Compared with cats without oral lesions, cats with oral lesions were more likely to be older, female, taking medications, drinking city (vs well) water, and playing less often with toys. In addition, cats without oral lesions were more likely to have owners who cleaned their teeth daily or twice a week and to be fed diets with higher magnesium, calcium, phosphorus, and potassium contents.

Clearly, the potential for tooth resorption is another excellent reason to develop the habit of brushing your cat’s teeth.

For more information and instruction on how to clean those tiny choppers, you can view my getting started video. You can also take a look at this in-depth video, which includes a 4-week training program.

Feeding your kitty balanced, raw, species-appropriate nutrition is another way to help prevent dental disease. When your cat gnaws on raw meat, it acts as both a toothbrush and floss. Homemade meals also give you control over the nutrients your pet is getting.

Cats can’t produce vitamin D in the skin, so diet is their only source of it. Since there are no upper limits on the amount of vitamins pet food manufacturers can include in their formulas, there are excessive amounts of vitamin D and vitamin D metabolites in some commercial cat food formulas. In recent years, at least one study has shown cats with tooth resorption have a significantly higher serum concentration of 25-hydroxyvitamin D (25OHD) than cats without lesions. Studies on laboratory animals show that excess dietary vitamin D and vitamin D metabolites cause changes to dental and gum tissue that in many ways resemble the changes seen in cats with tooth resorption. Kitties with tooth resorption also had significantly lower urine specific gravity, which is a marker for a number of disorders including hyperthyroidism, diabetes and kidney disease. Studies have shown excessive amounts of vitamin D and its metabolites are associated with soft tissue mineralization and renal disease.

This article was republished with permission. Dr. Becker is the resident proactive and integrative  wellness veterinarian of You can learn holistic ways  of preventing illness in your pets by subscribing to,  an online resource for animal lovers. For more pet care tips, subscribe for  FREE to Mercola  Healthy Pet Newsletter.

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11 Comments on Tooth Resorption: A Painfully Common Dental Disease in Cats

  1. If a cat has feline tooth resorption, can humans contract the disease or develop cavities as a result from the cat?
    Thank you

  2. This is very interesting and I wonder if anyone has explored it deeper to determine the role of Vitamin D in cat health and renal issues.

    Might you have other posts or studies on this correlation?

  3. This is great information. My cat, Ansgar, has lost 6 teeth to resorption – most recently 2 upper canines and 2 upper premolars just a few weeks ago. With his history, I’m concerned that he’ll lose more teeth to resorption – and he’s only 8 years old.

  4. I only feed my cats raw food and freeze dried treats. After their 1st dental cleanings last year, I started brushing their teeth daily. Just went for my yearly exam and my one cat has these lesions beginning on all four canines! I hope someone figures out what causes these lesions. Soooo frustrating…..

  5. Thank you for posting this! So many people think tooth resorption is “cavities” – and it’s not. I think the most important take-away is that its origins are a mystery. It’s not something that a vet can prevent. Or fix. Because of that, it’s especially important to feed a good diet *and* clean their teeth!

    Also, most people don’t realize that for the first day or so plaque is relatively easy to remove from the teeth – it’s only after about 72 hours that it becomes hardened into tartar and becomes impossible to remove via brushing.

    (Can you tell I’m passionate about this? Perhaps it’s because Maxwell has stomatitis/gingivitis and the beginning indication of a resorptive lesion on a back molar. Perhaps it’s also on my mind so heavily because, as I type this, he’s anesthetized and getting them cleaned/extracted!)

    • That’s an excellent point about plaque hardening after 72 hours – yet another reason to brush every day. I hope Maxwell did well during his dental today and is recovering quickly.

  6. That is a very interesting post about this disease of the teeth. We have had a lot of Stomatitis here with all the cats here. So far they are all doing all right. Never heard of this before. Thanks for the info. Take care.

    • Feline resorptive lesions are actually far more common than stomatitis. I’m sorry you had to deal with so much stomatitis, Marg – that’s a very frustrating condition, for cats and the humans who care for them. Look for a post on stomatitis next week!

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