Plaque is an invisible, sticky film composed mainly of bacteria. Plaque forms on your teeth when starches and sugars in food interact with bacteria normally found in your mouth. Brushing your teeth removes plaque. But plaque re-forms quickly, usually within 24 hours. Plaque that stays on your teeth longer than two or three days can harden under your gumline into tartar (calculus). Tartar makes plaque more difficult to remove and acts as a reservoir for bacteria. What's more, you usually can't get rid of tartar by brushing and flossing — you need a professional dental cleaning to remove it. The longer that plaque and tartar remain on your teeth, the more they irritate the gingiva, the part of your gum around the base of your teeth. In time, your gums become swollen and bleed easily. If not corrected, it could result in the loss of teeth or serious health problems.