Feline odontoclastic resorptive lesion

  Feline odontoclastic resorptive lesions (FORLs) is a disease in cats characterized by resorption of the tooth by odontoclasts, a cell similar to an osteoclast. A FORL is also known as a neck lesion, cervical neck lesion, cervical line erosion, feline caries, or feline cavity. It is one of the most common disease of domestic cats, affecting up to two-thirds.^[1] FORLs have been seen more recently in the history of feline medicine due to the advancing ages of cats^[2], but 800 year old cat skeletons have shown evidence of this disease.^[3] Purebred cats, especially Siamese and Persians, may be more susceptible.^[4]

  FORLs appear as erosions of the surface of the tooth at the gingival border. They are often covered with calculus or gingival tissue. It is a progressive disease, usually starting with loss of cementum and dentin and leading to penetration of the pulp cavity. Resorption continues up the dentinal tubules into the tooth crown. The enamel is also resorbed or undermined to the point of tooth fracture. Resorbed cementum and dentin is replaced with bone-like tissue.

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Symptoms

  Symptoms of FORLs include mouth pain (caused by dentin exposure), especially while chewing, anorexia, dehydration, weight loss, and tooth fracture. The lower third premolar is the most commonly affected tooth.^[2]

Cause

The definitive cause of FORLs is unknown, but histologically destruction of the cementum and other mineralized tissue of the tooth root by odontoclasts is seen. It occurs secondary to the loss of the protective covering of the root (the periodontal ligaments) and possibly to a stimulus such as periodontal disease and the release of cytokines, leading to odontoclast migration.^[5] However, FORLs can develop in the absence of inflammation.^[2] The natural inhibition to root resorption provided by the lining of the root may be altered by increased amounts of Vitamin D, in cats supplied by their diet.^[3]

Treatment

Treatment for FORLs is limited to tooth extraction to create a mouth free of pain. Amputation of the tooth crown without root removal has also been advocated in cases free of periodontal disease because the roots often completely resorb.^[6] However, X-rays are recommended prior to this treatment to document root resorption and lack of the periodontal ligament.^[7]

Tooth restoration is not recommended because resorption of the tooth will continue underneath the restoration. Use of alendronate has been studied to prevent FORLs and decrease progression of existing lesions.

Differential diagnosis: dental caries

True dental caries are uncommon among companion animals.^[8] Although rarely seen in cats, the incidence of caries in dogs has been estimated at approximately 5%.^[9] The term feline cavities is commonly used to refer to FORLs, however, sacchrolytic acid-producing bacteria are not involved in this condition.

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