Tooth decay destroys a tooth’s outer surface from acid-forming bacteria produced by food containing carbohydrates (sugars and starches). Tooth Decay Prevention: Brush your teeth twice a day with fluoride toothpaste. Preferably, brush after each meal and before bedtime to help prevent bacteria from staying on your teeth for a certain length. Consider these helpful tips: Floss your teeth daily to prevent tooth decay and gum disease. Check with your dentist about using supplemental fluoride, which strengthens your teeth and helps prevent tooth decay. Consider dental sealants; sealants are placed on the top of the molars to protect the teeth from decay. Use mouthwashes with fluoride. Many kill 50% or more of the bacteria that cause tooth decay. Chewing gum with the ingredient Xylitol © may also kill some of the bacteria that cause tooth decay.