Tooth Resorption in Cats

By Malcolm Weir, DVM, MSc, MPH; Lorraine Hiscox DVM FAVD Dip. AVDC; Jan Bellows, DVM, Dipl. AVDC, ABVP

What is tooth resorption?

Tooth resorption is a process by which the dentin (a hard tissue that lies beneath the enamel of the tooth) erodes and eventually becomes irreversibly destroyed. Over time, all areas of an affected tooth may become involved. In the past, tooth resorption was referred to as feline oral resorptive lesions (FORLs), feline odontoclastic resorptions, cavities, caries, cervical neck lesions, external or internal root resorptions, and cervical line erosions.

The most affected teeth are the premolars of the lower jaws (specifically the third premolars). In one study, 53% of cats had an obvious tooth resorption lesion and where no obvious lesion was noted clinically, X-rays (radiographs) revealed one almost 50% of the time.

What causes tooth resorption?

The exact cause of tooth resorption is unknown. Diet is believed to play a role. Other factors theorized to predispose a cat to resorption include frequent vomiting, periodontal disease, and mineral excesses or deficiencies in food or water. Tooth resorption in cats refers to a specific and painful condition.

Are there different types of tooth resorption?

X-ray of a cat's jaw that shows a tooth undergoing resorption. Part of the root is disintegrating.Tooth resorption in cats is divided into specific types based on the X-ray (radiographic) appearance of the root. X-rays of a normal tooth show the root with a characteristic density and a thin, dark outline around the root that separates it from the bone. The dark outline represents the periodontal ligament, a normal anatomic feature that attaches the root to the bone.

With type 1 tooth resorption, there is destruction of the crown but, radiographically, the root retains a normal appearance with an easily visible periodontal ligament.

With type 2 tooth resorption, radiographically the root appears to be disintegrating and is not distinct from bone. This is referred to as replacement resorption.

Teeth can also be classified as being type 3 tooth resorption, meaning they show features of both type 1 and type 2.

While the cause for tooth resorption remains unknown, type 1 tooth resorption has been linked to periodontal disease. Whatever the underlying cause, the result is loss of the outer hard tissue of the tooth (enamel, cementum, and dentin). Both types of lesions can affect the crown of the tooth as well as the root. Lesions that affect the tooth crown are very painful and require treatment.

How do I know if my cat has tooth resorption?

A cat's tooth showing the subtle signs of tooth resorption that may be seen on a physical exam.Once the sensitive dentin is exposed, tooth resorption is painful and manifests as muscular spasms or trembling of the jaw whenever the lesion is touched.

If your cat has tooth resorption, she may show increased salivation, oral bleeding, or difficulty eating. In many cases, without radiographic and clinical screening in an anesthetized cat, tooth resorption will go undetected, and the cat will be in pain in silence. Annual, thorough examinations with X-rays are recommended for maintenance of oral health and early detection of disease.

How is tooth resorption treated?

Treatment is guided by the radiographic appearance of the tooth resorption. With type 1 tooth resorption, both the crown and root need to be extracted. With type 2 tooth resorption, a technique known as crown amputation with intentional root retention is appropriate. Your veterinarian will obtain X-rays of the teeth to assess the type of resorption.

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