Your tooth does not develop cavities just overnight. It can take months, or even years, for the decay process to form cavities. The tooth goes through demineralization and remineralisation cycle all day long. Situations like heavy dental plaque, intake of sugary or sticky food, frequent snacking, etc. can cause the demineralisation process to exceed remineralisation. When demineralisation gets the upper hand, the enamel or cementum progressively breaks down producing cavities or holes in the tooth.