What is the main reason for tooth decay over time?

Bacteria and sugar: And by sugar i mean any carbohydrate. The bacteria eat carbs and produce acids which take calcium out of the tooth. Some acidic foods such as pop do the same thing. The best defense is flossing, brushing, avoiding pop and othe highly refined sugars, plus regular dental visits.

Bacteria and acid: The bacteria that reside in your moth produce acid as a by product which dissolves the mineral matrix of your teeth. Proper home care and professional hygiene visits will help minimize decay.

Some reasons exist: Tooth decay is a disease of the tooth structure that results from inadequate oral hygiene, poor eating habits and genetic predisposition. Bacteria present in the oral cavity use the sugars in some foods also known as fermentable carbohydrates to produce acids that will dissolve the enamel and dentin causing destruction of tooth structure and subsequent symptoms of discomfort if left untreated.