A Cavity or dental caries develops when a tooth or part of the tooth gets infected with bacteria and breaks down.It develops a hole that can grow bigger and deeper as it progresses.

Inside mouth ,various bacteria are present. When you eat sticky or sugary foods, these bacteria change some of the sugars in foods to acids.Now the bacteria which are present in oral cavity join with these acids and form plaque.The plaque acids stick on the tooth substances and attack the outermost layer of the tooth called enamel. The acids then continue to attack the inside parts of the tooth. This is what leads to TOOTHACHE!!