Tooth resorption is common in cats and, because of increased use of intraoral radiology, is clinically emerging in dogs. Recognition and treatment of tooth resorption in dogs is essential. Anatomically, the buccal surfaces of the mandibular premolars are most commonly affected. In some cases, the overlying gingiva appears hyperplastic and inflamed, but in others there is no visible abnormality to indicate pathology.
Tooth resorption can be classified by the extent of lesion progression, radiographic appearance, anatomic location, and cause. For treatment planning, it is important to know if the resorption is internal or external and, if external, whether the lesion has extended to the oral cavity.
Related Article: Feline Tooth Resorption—Extraction of Retained Premolar Root
1. Classification by Extent
Stage 1: Minimal hard tissue (cementum or cementum and enamel) loss.
Stage 2: Moderate hard tissue loss (with loss of dentin not extending into pulp cavity) (See Figures 1A, 1B, and 1C).
Stage 3: Deep hard tissue loss (extending into pulp cavity). Most of the tooth retains integrity.
Stage 4: Extensive hard tissue loss. Most of the tooth loses integrity. In stage 4A (See Figure 1D), the crown and root are equally affected; in stage 4B (See Figure 1E), the crown is more severely affected than the root; in stage 4C (See Figure 1F), the root is more severely affected than the crown.
Stage 5: Remnants of hard tissue are visible only as irregular radiopacities, and gingival covering is complete.
Figure 1A. Clinical appearance of tooth resorption extending into the oral cavity.