Dentin is not only a major part of your teeth but makes up the entirety of elephant ivory. Found under the enamel it is key in support the harder outer service and protection of the sensitive pulp at the centre. Being under the semi-transparent enamel, dentin plays an important role in determining the colour of your teeth. Dentin is made of microscopic tubes of dentinal fluids containing many minerals, primarily calcium. The dentin is both more pliable and more permeable than the surrounding enamel. As your Bristol dentist will tell you, this gives your teeth the advantage of flexibility but the greater risk of tooth decay. Tooth sensitivity is often caused by the exposure of the dentin through the loss of the enamel. The dentin has three levels: primary, secondary and tertiary. The majority of dentin is primary and found in between the enamel and pulp chamber. Primary dentin is a mixture of mantle dentin, at the closest point to the enamel and newly formed predentin which is not fully mineralised. After root formation is complete (once it is a functional tooth), secondary dentin is produced incrementally around the pulp chamber and gradually shrinks the pulp chamber of teeth. Tertiary dentin only appears through the occurrence of cavities and other external stimulus. The severity and duration of external damage determines the formation and structure of tertiary dentin.