Tooth Resorption in the Domestic Cat

Introduction

Tooth resorption in cats (also called feline odontoclastic resorptive lesions or FORL) is often confused with hard tissue defects that are not resorptive in nature, such as caries (tooth decay). Caries, however, is an infectious disease, characterized by demineralization of the inorganic portion and destruction of the organic substance of the tooth secondary to highly-refined sugar fermentation by cariogenic bacteria. Caries is extremely rare in cats and does occur in about 5% of dogs.Tooth resorption in cats (also called feline odontoclastic resorptive lesions or FORL) is often confused with hard tissue defects that are not resorptive in nature, such as caries (tooth decay). Caries, however, is an infectious disease, characterized by demineralization of the inorganic portion and destruction of the organic substance of the tooth secondary to highly-refined sugar fermentation by cariogenic bacteria. Caries is extremely rare in cats and does occur in about 5% of dogs.

Clinical Signs and Diagnosis

Most affected cats will not show distinct clinical signs, as tooth resorption below the gingival margin usually is asymptomatic. Pain may be present if the resorptive process affects the tooth crown and inflamed granulation tissue covers the defect after exposure to oral bacteria. Spontaneous repetitive lower jaw motions (jaw chattering) are sometimes reported while eating, drinking, or grooming. Crown defects may be detected at the gingival margin near the cementoenamel junction by means of a dental explorer. In advanced stages the crown can fracture off, leaving clinical or radiographic evidence of root remnants (sometimes the crown has broken off, and the gingiva has grown over the root remnant, leaving a visible bulge underneath intact gingiva or gingival with a sinus tract). Some cats exhibit abnormal extrusion of their canine teeth, which may be accompanied by thickening of alveolar bone. Dental radiography is essential in diagnosing dentoalveolar ankylosis and root replacement resorption that manifest before clinically apparent lesions occur at the tooth crown.

Histological and Radiographic Features of Tooth Resorption

Tooth resorption is caused by odontoclasts and starts anywhere on the root (not the crown!) surface and not always close to the cementoenamel junction (but often at the root apex or mid root area). Resorption of enamel may occur when root resorption has progressed coronally into crown dentin. The enamel may then become undermined or penetrated by the resorption process. Exposure to oral bacteria results in formation of highly vascular and inflamed granulation tissue. These defects may be painful and bleed easily when probed with a dental instrument. One characteristic feature of inflammatory root resorption is that the alveolar bone adjacent to the tooth defect is also resorbed. In a recent histological study, clinically and radiographically healthy teeth from cats with tooth resorption on other teeth showed hyperemia, edema and degeneration of the periodontal ligament with fiber disorientation, increased osteoid formation along alveolar bone surfaces, increased cementum formation along root surfaces, gradual narrowing of the periodontal space and areas of ankylotic fusion (dentoalveolar anylosis) between the tooth and alveolar bone. These findings suggest that prior to obvious resorption the very early lesion is not inflammatory in nature. Ankylosed roots are at risk to be incorporated into the normal bone remodeling process, resulting in gradual resorption of the root and replacement by bone (replacement resorption). [...]