Dental Resorptive Lesions

Resorptive lesions are known under many different names: "cervical neck lesions", "feline odontoclastic resorptive lesions (FORLs)", or "feline caries".  These lesions are commonly found in cats, but can also occur rarely in dogs.  

To understand what resorptive lesions are, we need to discuss a few things about normal tooth anatomy. 
  • The part of the tooth that is visible when you look inside the mouth is called the "tooth crown".  The parts below the gumline are called the "tooth roots".  The dashed blue line on the left shows where the gumline lies.  Both cats and dogs possess teeth with single, double, and triple roots. 
  • Within each tooth is a chamber or "root canal" that contains the tooth's blood vessels and nerves.  These vessels and nerves then communicate with the rest of the body.  This connection allows bacteria from a tooth infection to travel to the rest of the body and cause infections in the kidneys, heart, and liver. 
  • The root canal is surrounded by a bony substance called "dentin", which accounts for the bulk of the tooth's structure. 
  • "Enamel" is the hard, white, thin, outer shell of the tooth.   
  • The "periodontal ligaments" is a microscopic layer that holds the tooth roots into the jaw bone. 
A resorptive lesion is basically a hole in the tooth that occurs when normal body cells called "odontoclasts" destroy or "resorb" the tooth surface.  Over time, the hole enlarges to expose the nerves  inside the root canal and cause pain.  Resorptive lesions can grow so large that the crown of the tooth may break off entirely.   

Despite ongoing research, no one has definitely proven what causes resorptive lesions to occur.  Some theories include: improper nutrition, viral infection, autoimmune disorder, genetic predisposition, or periodontal infection. 

Any cat can develop resorptive lesions, but Siamese, Persians, and Abyssinians appear to be more susceptible.  Cats of all ages can develop resorptive lesions, but most pets are diagnosed between the ages of 4 and 6 years. 
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Symptoms of resorptive lesions:
Often these lesions start just below the gumline or are covered with gum tissue or tartar and, therefore, may be difficult to detect without a thorough oral examination. Cats are particularly good at hiding symptoms of discomfort, but you may notice:
  • mouth pain - your cat may avoid you tying to pet around the face or the lower jaw may "chatter" when you press around the gums.
  • excessive drooling
  • trouble eating - your cat may eat smaller meals, prefer to only chew with one side of the mouth, may gulp food instead of chewing and thus be more predisposed to vomiting, drop food out of the mouth, or seem to hesitate before eating.
  • weight loss

Your veterinarian may identify these lesions during a routine checkup if your cat will allow an oral exam or during a dental cleaning under general anesthesia.  A dental probe instrument can be used to identify the lesions or xrays may also be used.  Resorptive lesions are progressive over time, so early identification and extraction of the affected tooth will prevent your cat having pain and infection. 

There is no clear way to prevent resorptive lesions from occurring, but we strongly recommend a dental examination at least once a year.  You should also talk to your veterinarian about methods for tartar prevention to keep other forms of dental disease at bay.