According to the American Veterinary Dental College (AVDC), periodontal disease is an infection caused by bacteria located on the teeth and in the tissues surrounding the teeth (periodontium). A thin, sticky film of carbohydrates, fats and proteins, called “pellicle,” coats the teeth. Oral bacteria enter this mixture to form dental plaque. Salivary calcium and other minerals further transform the plaque into a hardened substance called calculus. Teeth brushing can remove plaque, however, not calculus. Plaque continues to accumulate and the bacteria infect the peridontium. Periodontitis is the infection of the periodontium, and the process is referred to as periodontal disease.