[Differential diagnosis of resorptive tooth diseases and caries]

Feline Odontoclastic Resorptive Lesions (FORL, previously known as "neck lesions") on cat teeth are compared to caries and differentiated with the use of new methods. Radiological examination reveals typical odontoclastic resorptive processes, which take place at the dental root and at the periodontium. These lesions demonstrate the destruction on the desmodontium and the following ankylosing reaction. The rhodamine B stain which is selective for caries, stains regions which are softened by caries in a dark red way. Fuchsin/Acetic-Light Green stained histological preparations demonstrate the resorptive lacunae, resorptive lagoons and resorptive canals. Giant cells with multiple nuclei and reparative cementum can also be shown with the same stain. Hardness measurements using a Knoop diamond (KHN Knoop hardness number) give information about the degree of hardness of the different tissues. Electron microscopic investigations are performed to show the dentinal tubules and allowing the differentiation between FORL and caries. Since FORL also has been found in wild cats we deduced that alimentation has no effect on the pathogenesis of the disease.