Look for anything that appears abnormal. The first sign of periodontal disease is redness of the gums. No matter how minor it seems, if this is present, the disease is present. The pet needs veterinary care in order to treat the disease and avoid all the problems associated with it. (See above, Is dental disease really a big deal?) If periodontal disease is not treated early, advanced signs of the disease include swelling of the gums, calculus on the teeth, receding gums, and mobile teeth. Any of these is a sign of advanced periodontal disease, and immediate medical attention is required.
Other things to watch for include swelling or masses, broken or worn teeth, and discoloration of the teeth. Any of these things should also be brought to the attention of a veterinarian right away.