Feline Odontoclastic Resorptive Lesions (FORLs)

Sometimes called Feline Oral Resorptive Lesions, FORLs are erosions of tooth enamel along the gum-line similar to cavities. Other names that have fallen out of favor include feline cavities, neck lesions, and cervical line lesions. Unlike cavities caused by saccharolytic bacteria, FORLs may occur before the presence of periodontal disease affecting the teeth and gums. The cause of FORLs is not completely understood, but the involvement of odontoclasts is seen microscopically. Odontoclasts are the cells normally responsible for absorbing deciduous (baby) teeth roots to allow adult teeth to erupt. It is speculated that these cells are triggered by an autoimmune response to dissolve adult tooth enamel. FORLs can be very painful as the protective enamel is eroded away, exposing the sensitive dentin and pulp beneath the tooth’s outer layers. They can cause drooling, anorexia, gradual weight loss, broken teeth or tooth loss, and secondary gum disease.

FORLs may be difficult to diagnose during a routine exam. This is one reason that prophylactic dental cleanings are vital to prevent advanced disease. If a cat is symptomatic, an exam – and as necessary, a dental cleaning – should be performed under anesthesia.

FORLs affect especially the lower premolars, but any tooth can be involved. There are 4 stages of progression to classify their severity. In the earliest stage, or stage I, the FORL is a small defect in the enamel that has not exposed the sensitive dentin underneath. When discovered at this stage, the tooth may be ultrasonically cleaned and thoroughly polished. Fluoride treatments can help to strengthen the enamel and slow the process of erosion to some degree.

Stage II lesions reach the dentin, and are usually painful. Symptoms may help determine the course of treatment to pursue with these teeth. If the cat exhibits signs of discomfort or has changed its eating habits, tooth extraction is probably warranted. Fluoride restorative products may help to desensitize the affected teeth, but data on long-term efficacy is inconclusive.

In Stage III FORLs, the defect has entered the pulp chamber as seen on oral radiography (X-rays), and extraction is eminent. Cats with Stage III lesions will often wince when touched around the face, and some cats may begin hiding or become aggressive. Their eating habits have, by this point, changed – sometimes realized in retrospect.

Stage IV FORLs are characterized by tooth fracture and advanced inflammatory changes in the gum tissue. Often, the crown of the tooth is missing, and gum tissue will attempt to cover the exposed root portion. This will usually become an infected, ulcerated, painful lesion that bleeds easily when probed. Tooth extraction or surgical exploration for residual root fragments is the only treatment option available at this point.

In cases that involve active inflammation, antibiotics are prescribed. And of course, pain should never go untreated. Analgesic drugs may be needed before and for a period after surgical treatment of FORLs.

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