FORL - Feline odontoclastic resorptive lesions
One of the most common dental disease in cats…

What is feline odontoclastic resorptive lesion disease?

It is one of the more common and most painful oral abnormalities seen in cats. It has been known to contribute to complications including chronic pain, chronic inflammation, behavior disorders, renal disease, gastritis, and hepatic lipidosis in cats. The feline odontoclastic resorptive lesion (FORL) is a hidden disease that is being recognized more and more in veterinary medicine due to the increase in knowledge and education about veterinary dentistry.

FORLs are aggressive, progressive and painfully destructive lesions that start in the bone surrounding the roots of cat’s teeth. Cells known as osteoclasts change in their activity, size and number it is thought due to lack of oxygen in the microenvironment. Once their behavior changes they eat through the cementum, dentin and tooth root structure replacing it with a disorganized and painful form of new bone. 

Once started, FORLs painfully progress through the root into the pulp chamber and up through the crown of the tooth until the remains of the tooth disintegrate. Because we are not sure what causes this disease it remains unpredictable and we are unable to prevent or protect cats from its destruction. Of the 20-70% of cats that are affected by this disease we have not found any common factors such as gender, age, sex, diet, or breed. A cat may have one or more teeth affected by the disease. Each tooth has its own defense mechanism and it is not clear why some cats have only a few lesions, and some cats end up with all their teeth affected by this disease. 

Approximately 20-70% of all cats worldwide are affected with this painful disease. Diagnosis of FORLs is only accomplished with regular veterinary professional oral examinations including x-rays of tooth roots and underlying periodontal bone. 

Clinical evidence of a FORL is usually noted when the lesions progress up into the cervical neck of the tooth or into the crown. At this point red granulation (protective or scar) tissue tries to fill the hole in the tooth creating the focal red-hot points in the gingiva of affected teeth.

Severely progressive lesions can have large sections of inflamed gingival tissue “growing” over and into the fractured crown and root. Long before this point, patients are experiencing severe pointed oral pain from exposure of the tooth root to air, liquids (water when drinking), acids in foods, and abrasion from grooming. 

Affected cats can have changes in appetite, eating patterns, grooming patterns, behavior changes such as antisocial activities but most will show minimal changes due to the animal reluctance too exhibit chronic pain.

What causes feline odontoclastic resorptive lesions?

The exact cause is unknown, but research shows a correlation between hypoxia and the resultant metabolic acidosis that causes precursors in cats to up-regulate normal osteoclast (bone eating cells) into a larger, more aggressive, and more prolific form. Biopsies of FORL lesions have shown these up-regulated osteoclasts in the area of destruction. 

Whatever the underlying cause, the process is irreversible, painful, results in chronic pain and ultimate loss of tooth structure from replacement resorption.  A study from UCDAVIS veterinary teaching hospital found an average of 4.9 lesions per mouth on affected felines.

How do I know if my cat has a feline odontoclastic resorptive lesion?

The best way to determine if your cat has FORL disease is with full mouth dental radiographs of each tooth and the surrounding bone. It is important to regularly screen your cat’s mouth for the disease as it can be a hidden cause of chronic pain and inflammation that disrupt your pet’s immune system. As the resorptive lesion erodes the root and extends into the sensitive pulp of the tooth, the cat begins to experience unrelenting tooth pain. Involuntary muscular spasms or trembling of the jaw occurs whenever liquids, pressure, or food touches the exposed nerves of the lesions.

Cats with FORLs may eat less food more frequently due to the pain encountered from eating. You as the owner may think that your cat is eating more because they make more frequent trips to the food or water bowl. In the stage of the disease where the crowns are being destroyed and the lesions have broken through into the mouth your cat may show increased salivation, oral bleeding, difficulty or reluctance to eat, cry out in pain when eating or drinking and become antisocial or demonstrate aggressive behavior towards other animals or family members.   

It is important to have your cat’s teeth regularly examined by your veterinarian and to have regular digital dental x-rays of teeth. Remember the process starts in the underlying bone interface with the tooth root and detection of the early stages of this disease can only be done with stages with dental x-rays.

How are feline odontoclastic resorptive lesions treated?

Once diagnosed, treatment of resorptive lesions is designed to relieve pain. Until the underlying process that causes this disease is understood veterinarians are unable to prevent or even predict this devastating disease. 

Once a lesion is confirmed with x-ray and examination under anesthesia, local pain/nerve blocks should be placed and the affected tooth surgically extracted, bone graft material placed in the extraction site, and the gingiva gently closed. Postoperative pain medications administered with oral antibiotics for 10-14 days.  

Cats are supported with soft food for two weeks while they heal and then can return to normal diet, oral play, and treats. Owners report that postoperative cats are significantly more active, playful and loving.

The extraction of teeth that have been altered by the FORL disease is difficult.  It is recommended that the cats with FORL’s found on general oral exam and x-ray be referred for confirmation of the disease, screening for early lesions, and treatment by a veterinarian that has the experience and training in the extraction of these teeth as well as safe advanced anesthesia techniques so that the time under anesthesia is minimized. Lesions that are missed in the early stages will progress and have to be extracted in the future.

The key to successfully managing this disease is early detection, early referral.

Dr. Brown has successfully treated over 6000 oral cases. She is extremely experienced at the diagnosis and extraction of FORL affected teeth. She offers a full oral exam, digital x-ray screening under anesthesia.  The average time under anesthesia for an oral screening is approximately 5 minutes. After which she will review the x-rays with you and make a plan to treat any disease that is found. Please call and set up an oral exam and digital x-ray screening for your feline patient today.  

Dr. Mary L Brown, DVM
Park Cities Center for Veterinary Dentistry
4230 West Lovers Lane
Dallas, TX 75209

214.864.7564
Fax- 214.352.5522
Website - www.pcvdos.com

Article provided by: Dr. Mary L Brown, DVM