Feline Odontoclastic Resorptive Lesions

FORLs

Typical Signalment

• There are no sex or breed predispositions
• Becomes more prevalent with increasing age

Description

Feline odontoclastic resorptive lesions (FORLs) are the most commonly seen dental lesions in cats. On examination, there is a loss of dental tissue on the crown or at the neck of the teeth. The crown may be completely resorbed with the remaining root covered with gingiva.

The aetiology and pathogenesis of FORLs has not yet been demonstrated but is almost certainly multifactorial. Possible hypotheses that have been suggested include:

• Diet texture
• Abnormal calcium regulation
• Hypervitaminosis A
• Mechanical stress
• Anatomical abnormalities of the teeth
• Viral infection
• Plaque bacteria and periodontal disease

Diagnosis

Clinical Signs

• Pain on contact
• Anorexia
• Drooling
• Lethargy

Oral Examination

Visual Examination - identification of the lesions or inflammed gingiva that overlies the remaining root.

Probe - lesions that are subgingival may be identified using a dental probe.

Diagnostic Imaging

Radiographic signs of FORLs include:

• Erosion of alveolar bone at the cementoenamel junction
• Root resorption
• Root ankylosis and subsequent periodontal space loss
• Resorption of the dental dental crown

Classifying the Lesions

Classifying the lesions allows a logical treatment regime to be implemented. It can bt based on the severity of the resorptive lesions.

• Stage 1 - Enamel only
• Stage 2 - Enamel and dentine
• Stage 3 - Pulp exposure
• Stage 4 - Extensive structural damage
• Stage 5a - Crown is resorbed but the roots are retained
• Stage 5b - Crown is intact but the root is resorbed

Treatment

There are various treatment options available for the different stages of disease.

• Stage 1-2
  • Scale and polish
  • Fluoride treatment
  • Pit and fissure sealant
• Stage 2
  • Scale and polish
  • Restoration of the tooth using glass ionomer, compomer or composite (High failure rate)
• Stage 2-4
  • Extraction
  • Crown amputation whilst retaining root
• Stage 5a
  • Extraction
  • Root retention
• Stage 5b
  • Crown amputation

References

• Tutt, C., Deeprose, J. and Crossley, D. (2007) BSAVA Manual of Canine and Feline Dentistry (3rd Edition) BSAVA

• Merck & Co (2008) The Merck Veterinary Manual

From Pathology

• Cats
  • Odontoclasts attack external and internal to the tooth.
  • Initially start at the neck/cervical region and extend into tooth root and also enter the root via the apical foramen (stage 3 lesions)
  • 20%+ of cats have them
  • Different from caries – demineralization by bacteria fermenting CHO on the enamel.
  • ORLs – only occur when odontoclasts resorb the tooth/bone
    • continues with remodeling of alveolar bone until ankylosis
    • fixation of periodontal ligament and lamina dura so that the tooth is permanently fixed to the bone.
• Odontoclasts normally only active in young animals to resorb the deciduous teeth to make way for the permanent teeth – so represents abnormal activation in adults.
• Can have inflammatory infiltrates into the resportive lesions