FORLs, or Feline Odontoclastic Resorptive Lesions, are one of the commonest causes of dental pain in cats – some studies suggest as many as 60% of cats are affected. However, these are not well understood, so in this blog, we’re going to explore this strange and unpleasant condition.

What is a FORL?

These lesions, also known as Neck Lesions, Feline Cavities, and Root Resorptions, are progressive lesions that attack the tooth near the line of the gum. The gum tissues become inflamed and then start to break down the outer layer of the tooth, the hard enamel. We call these Class 1 lesions. If unstopped, the damage progresses, eating through the softer dentine (Class 2) and into the sensitive pulp cavity around the nerve (Class 3). Eventually, the tooth is so weakened that it snaps off, leaving the root behind in its socket (Class 4).

What causes them?

Unfortunately, the cause is not yet known. Some researchers have suggested that an excess of vitamin D in the diet may be a factor, but this is not a widely held opinion. However, infection with a range of viruses, and chronic diseases such as kidney or liver failure are known to be risk factors. As a result, the current “best theory” is that the FORLs are an abnormal response of the cat’s immune system – an inflammatory reaction that results in an exaggerated reaction of the cells at the gum line, and as a side effect, damage to the teeth.

Additionally, regular dental care (especially tooth brushing) does seem to give some protection against the lesions. This is presumably by reducing the numbers of bacteria present and thus reducing the stimulation of the immune system.

In any case, older cats are at higher risk – FORLs are relatively uncommon in cats under 4 years of age, and the average age is a little under 10 years old.

What are the symptoms?

The most common symptom is discomfort when eating. The worse the lesion becomes, the more painful it is. Although some cats may show obvious signs of pain, in most cases, the condition is characterised by slow eating, eating with the head tilted or only chewing on one side, reluctance to eat, and pain or aggression when the affected side of the head is touched. That said, cats are very tough and stoical creatures, and in many cases the only sign of even multiple severe lesions is a cat who suddenly stops chewing, or develops a preference for soft or wet food.

How are they diagnosed?

While FORLs may become clearly visible during routine dental surgery, unfortunately all too often it’s because an apparently healthy tooth has snapped off while being examined. This is because the lesion is down below the gum line. The most sensitive way to diagnose a FORL is with radiographs, using a specialised dental X-ray system to allow us to locate and diagnose the lesions before going to surgery, minimising the risk of damage to the delicate tooth roots.

What is the treatment?

Early Class 1 FORLs may be manageable with dental polishing followed by careful and regular tooth brushing. While this does not prevent progression of the lesion, it may slow it down. If there is a diagnosed underlying condition, such as kidney disease, or calicivirus infections, then treating that may, again slow down the progress.

Most of the more severe lesions usually require tooth extractions, sadly. It is vitally important to remove the roots, as otherwise the lesions (and the pain and distress they cause) will continue underneath the healed over gum.

If your cat has any signs of dental problems – please contact us immediately! We are fully equipped to offer sophisticated dental diagnosis and surgery, and will be more than able to help your cat.