by Barry B. Burtis D.V.M.
Dental Resorptive Lesions in Cats
February is Pet Dental Health Month. I want to focus on a dental condition in cats that is very prominent and quite specific to them. It is called Feline Odontoclastic Resorptive Lesions (FORL) or dental resorptive lesions. They used to be referred to as caries, then we called them cavities (because a hole develops in an affected tooth), then feline neck lesions (because they develop in the neck of the tooth in cats) and several other names have been used. FORL is one of the current terms used and describes in more detail the nature of the destructive process. Veterinarians now understand better what is happening in affected teeth, but, do not have complete answers to the problem.
It is a very common condition in cats. One or more FOR lesions is found in about 50% of the domestic cat population aged 4 years or more. At the microscopic level this is what happens. The problem begins when plaque bacteria cause inflammation in gum tissues. Chemicals that result cause the cat's body to respond by producing tissue cells called odontoclasts. Odontoclasts begin to resorb or break down parts of the affected tooth. Cells try to respond to this breakdown and repair the defect but they fall behind when there is poor blood supply to the area and eventually the entire tooth can be destroyed.
To recognize the problem it is necessary to look closely at each individual tooth in a cat's mouth. Most cat owners will realize this is not a very easy thing for them to do. Unless the cat is quite cooperative, even a veterinarian giving it a general physical examination, may get only brief glimpses of the teeth. Therefore, often FOR lesions are not diagnosed until the patient is undergoing a dental examination while under sedation or general anesthesia. The lesions start as a small dot of inflamed tissue at the tooth and gum margin. The erosion progresses through the enamel into deeper layers of the tooth where it may spread in any direction. Untreated, it will eventually reach the internal part of the tooth.
FOR lesions are painful. Cats, in most cases, ignore the pain associated with food and water touching these lesions when they eat and drink. It is unusual for a cat to refuse food even when multiple resorptive lesions are present. However, if they are touched directly in a dental examination, even if the cat is sedated or under light general anesthesia, a pain response will be noted.
Veterinarians and veterinary dentists have used various methods to respond to the problem. Dental x-rays are important and helpful in determining how much of a tooth is affected. Glass ionomer fillings have been used to repair affected teeth. Unfortunately, since FORL are not comparable to cavities seen in other animals, fillings proved to be quite unsuccessful as a treatment. At present, if teeth are determined to be significantly affected by the disease, it is probably best to extract them.
There has been an increase in the number of cats who have resorptive lesions since 1969. We do not know the reason for this nor the actual cause of this dental disease. There are two current theories that have been proposed. One suggests it may result from abfraction forces on the tooth associated with eating dry cat food. The other has to do with periodontal disease and how its occurrence will lead to FORL. Wet food leads to more plaque and calculus formation and therefore increases the risk of developing periodontal disease.
Meanwhile, what are cat owners to do? A plaque or calculus reducing dental treat may be beneficial. Cats that have frequent dental cleanings and care by a veterinarian and have their teeth brushed daily or twice a week seem to have fewer resorptive lesions. Ingesting increased levels of magnesium, calcium, phosphorous and potassium may also be helpful. One authority notes that there seem to be fewer resorptive lesions in those cats that floss regularly with mouse tails!