Periodontal Disease, or gum disease as it's commonly known, is a disease that affects the structures around the teeth. The widely accepted cause of this disease is thought to be from bacteria.
Periodontal disease is caused by the bacteria within dental plaque. This plaque, left untreated, then begins to affect the structures surrounding the teeth, which includes your gums.
The first thing one can do in preventing Periodontal Disease is practicing good oral hygiene. This includes daily brushing and flossing.
It is extremely important to note, however, that if you already have the onset of this disease then you will need to schedule a visit with a periodontal specialist near you to learn about your treatment options.