Enamel is the hardest outer layer of a tooth. Dentin is the next softer layer beneath the enamel. Beneath the dentin is the pulp which contains nerve and blood vessels. If the tooth is not cleaned well, bacteria accumulate on the tooth surface, producing acid which demineralizes the enamel. This leads to cavity/decay/caries formation. This cavity has to be cleaned and filled by a dentist. If it's not treated, the decay reaches into the dentin, the softer layer. For more details please contact us! 9810560566