Plaque is essentially the start of gum disease problems. Plaque is a build-up from bacteria in the mouth and particles from the foods you eat every day.
Once sugars are introduced to plaque, it turns into a tooth eating acid that sits just above the gum line. If regular oral care isn't standard, the acid will start eating at the teeth producing cavities and the plaque will cause gum disease.
Plaque that is allowed to sit for a prolonged period of time can cause cavities, gingivitis, and other problems in your mouth. If it's left longer than that, serious dental procedures may be required to restore your decaying smile.