You might be in the early stages of gum disease (gingivitis) or in the more advanced stage (periodontists). A buildup of plaque, a sticky bacteria, below the gum line causes it. Left untreated, periodontists can cause bone loss, and your teeth might shift or become loose. That can make it harder to chew and even speak. To avoid gum disease, brush and floss daily, and see your dentist for regular cleanings.