How do i have decayed teeth?

Sweet and hygiene: Decay is the result of removal of your calcium of your tooth structure by bacteria also known as a "sugar bug". After consuming carbohydrate or sweets in food, the left overs caught in the tiny space or corner of teeth will allow bacteria to eat and poop on surface of the tooth. The acid of the poop is the main factor to erode the enamel.

Combo: Cavities are caused by a combination of factors: bacteria that is always present in your mouth, poor oral hygiene, consumption of sugary drinks or food. Rec.: see your general dentist for a professional cleaning and prophylaxis. Ask your dentist how you can keep your teeth for the rest of your life?

Bacteria and sugar: Decay is caused by bacteria which are naturally occurring in your mouth. When the bacteria are fed sugar, either simple like sweets or complex like bread or sugar, they produce acid which eats into the tooth.