What is tooth decay? Tooth decay is a preventable disease caused by a combination of plaque, sugar consumption and poor oral hygiene. The bacteria living in plaque turn the sugar in the food and drinks we consume into acid. This acid damages the enamel layer of our teeth creating a cavity with repeated acid attacks. The more often we consume sugar, the more frequently our teeth will be under attack. Stages of tooth decay Decay in its very early stages can be reversed. Earl