고양이 치아 흡수성 병변(FORLs) 증상과 원인, 진단·치료와 관리 포인트 총정리

Feline Odontoclastic Resorptive Lesions (FORLs): Symptoms, Causes, Diagnosis, Treatment, and Management Essentials

Oral HealthDiseasesMeongsiljang Veterinary Advisory Board

Feline odontoclastic resorptive lesions (FORLs) are a dental condition in which the enamel and dentin of the teeth gradually break down. Because they can cause pain, early detection is essential.

What are Feline Odontoclastic Resorptive Lesions (FORLs)?

The inside of a cat's mouth showing tooth resorption lesions

Feline odontoclastic resorptive lesions (FORLs, formerly known as feline odontoclastic resorptive lesions) are non-carious diseases in which the hard tissues that make up the teeth (cementum, dentin, and enamel) are gradually destroyed and absorbed by odontoclasts. Resorption usually begins on the surface of the tooth root, particularly in the cementum, but can occur anywhere on the tooth. Although FORLs can cause pain, cats often do not show obvious signs, making early detection difficult. - Characteristics of FORLs: Abnormal resorption starts in the cementum on the surface of the tooth root, with little to no visible changes in the early stages. - Stages of lesion progression: According to the American Veterinary Dental College (AVDC), lesions are classified into stages 1 through 4, with deeper loss of hard tissue leading to increased pain and tooth damage. - Consequences of tooth damage: Teeth may become loose, or the root may be absorbed, causing the tooth to break or disappear. - Importance of early detection: It is important to have your cat examined by a veterinarian for early diagnosis before the pain becomes severe.

What are the main causes of FORLs?

The exact cause of FORLs remains unknown, but several contributing factors have been proposed. - Excess dietary vitamin D: Chronic overconsumption of vitamin D has been suggested as a potential cause of resorptive tooth lesions. - Hard food and pressure damage: One theory suggests that pressure damage (abfraction) from chewing dry kibble may be linked to these lesions. - Oral inflammation: Type 1 lesions are relatively often associated with chronic oral inflammation, such as gingivitis, periodontitis, and stomatitis. - Age-related correlation: The likelihood of developing Type 2 lesions increases with age, making early management especially important for older cats. However, no theory has yet established a clear causal relationship, and FORLs are known to be unrelated to retroviral infections.

An anatomical illustration showing the process of tooth resorption in cats

What are the main symptoms of FORLs?

Feline tooth resorption lesions often show few symptoms in the early stages, but gradually exhibit the following signs:

Worsening bad breath: Bacterial growth in the mouth occurs due to dental lesions.

Reluctance to eat: Pain when opening the mouth or chewing.

Increased frequency of licking: Repetitive licking behavior to relieve pain.

Opening or shaking the mouth: Often seen when pain arises from tooth resorption.

Swallowing food without chewing: Avoiding chewing due to pain.

These behaviors make early detection challenging.

When to Visit the Vet Immediately

If your cat stops eating, starts licking its lips much more frequently, or develops a strong bad breath, consult your veterinarian right away. As pain worsens, treatment becomes more difficult.

How are FORLs diagnosed?

Because FORLs are often not visible on the surface, specialized testing is required for an accurate diagnosis. - Dental X-rays: These allow for a detailed assessment of the tooth roots and surrounding bone. They are essential for evaluating the extent of root resorption and identifying changes in the periodontal ligament and dental tissues. - Oral probe (dental explorer) examination: A fine-tipped probe is used to directly detect resorptive defects on the tooth surface. Even if teeth appear healthy externally, radiographic or histological changes may be present. - Comprehensive oral examination under anesthesia: The veterinarian comprehensively evaluates the location, size, and progression of lesions in conjunction with X-ray findings. - Regular check-ups recommended: As the risk increases with age, it is advisable to undergo regular oral examinations, including dental X-rays. Early detection aids in pain management and treatment.

Dental X-ray showing feline tooth resorption lesions

What are the treatment options for FORLs?

Treatment for FORLs depends on the severity of the lesions. In most cases, the key is extracting the affected tooth to eliminate the source of pain.

Tooth extraction: The diseased tooth is removed to eliminate the cause of pain.

Crown amputation: If the tooth root has already undergone resorption or ankylosis (fusion to the bone), making complete extraction difficult, and there are no radiographic signs of periapical or root canal lesions, only the crown may be removed while leaving the resorbing root in place.

Pain management: Pain is appropriately managed before and after the procedure.

Oral care: Strict oral hygiene is maintained after the procedure.

The treatment plan is determined by the veterinarian based on radiographic evaluation. With appropriate treatment, pain decreases and the pet’s ability to eat improves.

A cat undergoing a tooth extraction procedure

Home Care Guidelines

Consistent care is essential even after treatment. Please be sure to follow these guidelines:

Oral Hygiene: Establish a daily habit of brushing your pet’s teeth. Using a toothbrush and toothpaste specifically designed for pets is recommended.

Dietary Management: Switch to soft or wet food to reduce strain on the teeth.

Regular Check-ups: Schedule oral examinations every six months.

Monitoring for Pain Signals: Closely observe for signs such as excessive lip-licking or reluctance to eat.

Communication with Your Veterinarian: Maintain regular contact with your vet to monitor your pet’s condition and ensure ongoing care.

Preventing Recurrence and Breed Considerations

FORLs often affect multiple permanent teeth, as lesions in one tooth are frequently accompanied by similar issues in other teeth within the same mouth. While there is no definitive evidence that certain breeds are more prone to this condition, the risk is known to increase with age. Therefore, regular, comprehensive oral examinations for early detection and management are essential to ensure no new lesions are missed, even after treating a single tooth.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Are FORLs a common condition in cats?

Yes, it's a common dental disease in older cats, and depending on the study group and diagnostic methods, it can be found in about 25% to 75% of cats.

Do FORLs cause pain?

Yes, tooth resorption can cause severe pain. Since cats are good at hiding discomfort, it’s important to watch for changes in their behavior.

Is it safe to have my pet’s teeth extracted?

Yes, tooth extraction is an effective way to eliminate the source of pain. Cats can eat and live normally even with some missing teeth. In cases where the tooth root is ankylosed or resorbed, only the crown may be removed.

Can it be prevented?

While there’s no proven preventive method yet, regular dental check-ups and at-home teeth care can help catch issues early.

Can FORLs spread to other teeth?

Yes, because the condition typically affects multiple permanent teeth, if one tooth develops a lesion, there’s a high likelihood that others will too. Comprehensive oral health care is essential.

Top Recommended Products and Selection Criteria for Preventing Tartar and Plaque in Dogs

Top 5 Recommended Pet Tartar Control Products for 2026

Top Recommended Products for Managing Canine Oral Fungal Infections and Selection Criteria

A Complete Guide to Frequent and Urgent Urination in Dogs: Symptoms, Causes, Diagnosis, Treatment, and Management

Neurogenic Bladder in Dogs: Symptoms, Causes, Diagnosis, Treatment, and Management Essentials

High Blood Pressure and Proteinuria in Dogs: Symptoms, Causes, Diagnosis, Treatment, and Management Essentials

Canine Hydronephrosis: Symptoms, Causes, Diagnosis, Treatment, and Management Essentials

Hematuria in Dogs: Symptoms, Causes, Diagnosis, Treatment, and Care Essentials

Dog Stranguria: Symptoms, Causes, Diagnosis, Treatment, and Care Essentials

Cystine Urolithiasis in Dogs: Symptoms, Causes, Diagnosis, Treatment, and Management Essentials

References

[1] Bellows J. Feline Dentistry – Oral Assessment, Treatment, and Preventative Care. 1st ed. Ames: Wiley-Blackwell; 2010.

[2] Thatcher CD, Hand MS, Remillard RL. Small animal clinical nutrition: an iterative process. In: Hand MS, Thatcher CD, Remillard RL, eds. Small Animal Clinical Nutrition. 5th ed. Topeka: Mark; 2010.

[3] Anderson JG, Harvey CE, Flax B. Clinical and radiographic evaluation of external odontoclastic resorptive lesions in cats (abstract). J Vet Intern Med. 1993;7:134.