If left untreated, resorptive lesions progress through five separate stages:
- Stage 1 — During the early stages the lesions only affect the tooth enamel and may go unnoticed because they have not begun to cause pain for the cat.
- Stage 2 — This involvs both enamel and dentin. Cats experience some discomfort, but it is often mild enough that a cat’s behavior may not be noticeably different
- Stage 3 — In this stage, the tooth’s pulp cavity is exposed and there is often intense pain. However, most cats will do all they can to mask pain, so the symptoms that owners do notice may not be all that dramatic.
- Stage 4 — During this stage, most of the tooth has been destroyed by the resorptive lesion.
- Stage 5 — Finally, the gums grow over the small amount of dental tissue that remains.