FORL lesions

FORL or resorptive lesions of teeth in cats are currently known under many names: in articles and proceedings, they have been referred to as cervical line lesions (CLL), cervical neck lesions (CNL), cervical line erosions, cervical line resorptions, subgingival resorptive lesions, osteoclastic resorptive lesions, feline dental resorptive (FDR) buccal cervical root resorptions, etc.

Our patient: "Seker” a spayed female Persian cat, 7 years old had heavy plaque and calculus accumulation (Fig.1), but what is worse was only visible after removing the calculus by means of ultrasound (Fig.2). The teeth on the right mandibular dental arcade had multiple FORL lesions of different stages (class 3 and 4 FORL lesions) clearly visible on the X-ray (Fig.3).

Clinical Signs

FORL lesions are common in domestic felines and periodontal disease is commonly found in association with such lesions. Lesions are often covered with hyperplastic or hyperemic gingiva and/or or calculus. The lesions are described as originating at the cervical or cemento-enamel junction of the tooth just below the gum line.

Radiographic examination in some individuals has demonstrated that lesions are present further apically on the root structure even without obvious cervical pathology. Lesions identified in early stages are located in the cervical area and occasionally found with a dental explorer during routine dental prophylaxis.

Clinical signs vary greatly according to the stage of lesion development, there may be slight to severe gingival inflammation, the gum tissue is hypertrophic and hyperemic, and this may progress to gum recession.

In principle, we differentiate between 5 classes (stages) of FORL lesions.

Class 1 lesion means that the surface of the enamel is superficially decalcified and the destruction is limited to the enamel which is either rough or shows a noticeable indentation already.

Class 2 the neck lesion has reached the dentin but not yet the pulp chamber. Class 2 is the final stage that might may be still successfully treated by a restoration filling. 

Class 3 the lesion has already reached the pulp. After removing the granulation tissue, which fills the cavity, a bleeding from the exposed pulp will be seen. 

With destructions of class 4, however, the neck lesion has gone beyond the pulp chamber. The crown is supported by only a very small enamel edge at the opposite wall.

In the most advanced stage of class 5, the crown is broken. Sharp remnants of the root can be felt with the carefully examining fingertip. These extremely sharp points often cause a chronic, granulomatous inflammation which will heal only after all root remnants have been removed. The treatment of choice for lesions beyond class 2 is extraction.

Some of the believed causes of FORL are:

* incorrect Ca/P ratio and / or excess intake of Vitamin D

* dry food and acid spray technique

* the importance of special strains of bacteria

* chronic inflammation

However the aetiology of  FORL remains a mystery and a clear aethiopathogenesis is still to be solved.

DDr. Camil Stoian PhD, Mag. Helene Widmann