Dental caries, or bacterial infections of the teeth, are common in people, uncommon in dogs, and essentially nonexistent in cats. This may be related to the fact that human saliva is more acidic, human teeth contain many pits and fissures, and the human diet is rich in highly refined carbohydrates. The saliva of dogs and cats is more alkaline than that of people, their teeth contain fewer pits and fissures, and their diet is less rich in carbohydrates. Furthermore, cariogenic bacteria are less common in the mouths of dogs and cats than in those of people. The initial lesion of caries is acidic demineralization of the enamel. This is accomplished by cariogenic bacteria that ferment sugar, thus releasing acids onto the tooth surface.
In dogs, caries usually occurs on the occlusal surfaces of molar teeth. It has the appearance of a brown to black cavitated lesion with a soft surface into which a sharp explorer tip can penetrate and “stick.”
The carious tooth structure must be removed using a dental bur until healthy dentin is reached. A radiograph should be taken to determine whether the infection has spread to the pulp, in which case the tooth also requires root canal therapy. The missing tooth structure is then restored using either composite or amalgam.
Dogs that have had dental caries are predisposed to additional lesions; topical treatment with a stannous fluoride product every 2 wk may help prevent future caries in these animals. Because dogs do not expectorate, they swallow any medications used. Therefore, only small amounts should be placed on the occlusal surfaces of the teeth. Fluoride can cause gastritis, and it can be nephrotoxic if significant amounts are ingested.