Forl in Cats

May 2005
Dr Gerhard Steenkamp

A 5 year-old DSH cat is presented to you for a routine scale and polish. While performing the procedure you notice the following lesions on the left lower canine (304) and the first mandibular premolar tooth on the same side (307).

A What diagnostic procedures would you perform in order to make a diagnosis
of these lesions?

B What is the pathogenesis of feline odontoclastic resorptive lesions (FORL)?

C Discuss treatment options for these 2 teeth

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A In order to accurately access each individual tooth, one should probe around the tooth to see if there is any increased probing depth, which would indicate periodontal disease around these teeth. Secondly an explorer should be used to assess the surface area of these teeth to rule out surface area defects such as resorption, fractures or caries. Lastly a radiograph should be taken to assess the root integrity of these teeth (See accompanying radiograph)

B Lesions usually start at the gingival margin of a tooth (hence the previous name ‘neck lesions’), but they can start anywhere on the crown or root (external) or in the pulp chamber (internal). At first the enamel has a rough feel to it as it is being destroyed. At this time it is often covered by a small amount of hyperplastic gingiva. The lesions are caused by multinucleated cells resembling osteoclasts. These cells eat away at the tooth substance. A cavity caused by ORL has walls of hard tooth substance (compare caries). As the cavity gets deeper it eventually penetrates the pulp. Unlike other traumatic or infective conditions, ORL seldomly kills the pulpal tissue. It would rather give rise to pulp hyperplasia and continuously painful pulp. Research aimed at understanding the aetiology of FORL’s is ongoing but no causative factor has yet been determined. FORL has also been described in wild cats as well as dogs and man. In none of these species however does FORL’s occur in the same incidence as domestic cats.

C Much have been tried over the last 10 years. Filling is not a viable option as the cause can not be removed (like caries). Extraction, at the moment, is the only treatment option with good predictability. Extraction is often impossible as ankylosis between alveolar bone and root makes it impossible to remove the tooth in one piece. Crown amputation has also proved very good results. It is however imperative that the clinician make absolutely sure there is no infection of the endodontic system concurrent with FORL’s. As these cases with pulp necrosis WILL result in periapical abscesses if the crowns are only amputated. After amputation all visible root material, intentionally left behind, should be covered with a gingival- or gingivo-mucosal flap.

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