Pet dental disease starts out as a bacterial film called plaque. The bacteria attaches to the teeth. When the bacteria die they can be calcified by calcium in saliva. This forms a hard, rough substance called tartar or calculus, which allows more plaque to accumulate. Initially, plaque is soft and brushing or chewing hard food and toys can dislodge it. If left to spread, plaque can lead to gingivitis, an inflammation of the gums, causing them to become red and swollen and to bleed easily. As plaque and calculus develop below the gum line, professional cleaning will be needed to help manage it. If the plaque and tartar buildup continues unchecked, infection can form around the root of the tooth.
In the final stages of periodontal disease, the tissues surrounding the tooth are destroyed, the bony socket holding the tooth in erodes, and the tooth becomes loose. This is a very painful process for your four-legged friend, but these problems can be averted before they start with proper dental care.