Management of feline odontoclastic resorptive lesions (FORL)

Feline odontoclastic resorptive lesion (FORL) is frequently detected in cats,¹ and is often underdiagnosed or confused with tooth fractures or caries.² FORL has an incidence of over 60% in patients with at least one affected tooth, and this percentage increases with age.¹

Studies carried out to date have been unable to discover the aetiology.²

Pathophysiology

Initially, the lesion takes the form of small perforations on the surface of the tooth, just below the gum line. As it progresses, the holes grow larger and become painful, until the crown breaks and exposes the roots inside the bone.³

This disease courses with destruction of dental tissue by osteoclast activation in the neck, root and/or dental crown. A high degree of tooth destruction can be observed in advanced cases.²

Clinical signs

Although cats with FORL may have halitosis, dysphagia, ptyalism, anorexia, dehydration, weight loss, lethargy and malaise, most do not manifest any characteristic clinical signs. Sneezing, excessive tongue movement or head shaking have also been observed.⁴

Diagnosis

Lesions manifest as dental destruction (external or internal resorption), particularly in the vicinity of the cemento–enamel junction and its apical regions. Hence, dental X-rays are essential for a detailed and proper study of the disease.¹

X-rays are necessary to determine if the resorptive defect has penetrated the pulp or to detect any periapical lucencies, which is important for the subsequent restoration treatment.⁴

The macroscopic exam can reveal various findings, as dental resorption at the neck of the tooth can often be detected with a probe, as can the formation of granulation tissue on the gums covering dental defects.¹

Pain is often clearly evident when exploring teeth with resorption lesions using a dental probe, even under general anaesthesia; hence the importance of the proper diagnosis and treatment of FORL.¹

Treatment

The ultimate aim of any treatment is to provide the cat with a healthy, pain-free mouth.⁴

The traditional approach is to apply fluoride to phase 1 lesions, restoration in phase 2 lesions, and extraction in phase 3 and beyond. Although it is frequently recommended, fluoride treatment has never actually been proven to prevent or slow resorptive lesions in cats.⁴

However, restoration is not performed on a regular basis because of its low long-term success rate. This high treatment failure rate is down to the delicate nature of feline teeth, poor preparation of the cavity, incorrect classification of lesions and, above all, the technical complexity of treating lesions in the cervical third of the root and gingival third of the crown.⁴

The progressive nature of FORLs combined with a lack of knowledge regarding the aetiology means that the most acceptable treatment at the moment is tooth extraction. It may hard to extract affected teeth because they become brittle and break easily, and removing the root is more complicated once the crown has fractured.⁴

In summary, we can conclude that:⁴

- Approximately one third of domestic cats may develop FORL at some point in their lifetime and the risk increases with age.

- The aetiology remains unknown.

- Tooth extraction is the current standard of treatment.

References:

1. Collados-Soto J. (2008). En Atlas visual de patologías dentales y orales en pequeños animales y exóticos;2-14. Servet.

2. Collados-Soto J. (2008). Patologías dentales. En Atlas visual de patologías dentales y orales en pequeños animales y exóticos;344-383. Servet.

3. Johnston N. San Román F. García P. Sánchez M. (1998) in San Román F (ed.)  Atlas de odontología en pequeños animales. Chap 15, p 269. Editores Médicos SA.

4. Reiter A.M., Mendoza KA. (2002). Feline odontoclastic resorptive lesions an unsolved enigma in veterinary dentistry. The Veterinary Clinics of North America. Small animal practice, 32(4), 791–837.