Gingivitis is the earliest stage of gum disease caused by a buildup of plaque and bacteria on the teeth. It causes red, swollen gums that bleed easily when brushing. Symptoms include bad breath and gum tenderness or pain when chewing. Gingivitis is usually diagnosed during a dental exam where the dentist evaluates the gums and checks for signs of infection and inflammation. Treatment involves improved oral hygiene through proper brushing and flossing to remove plaque and bacteria from the teeth and gums. Left untreated, gingivitis can advance to a more serious form of gum disease called periodontitis.