Dentin is the most abundant dental tissue determines the size and shape of teeth. Dentin is a bone-like substance that is formed by odontoblast cell which make up most of the structure the tooth. Dentin is found just under the enamel in the crown and under the cementum in the root. The unique structure and composition of dentin allows it to function as the substructure for rigid enamel tissue thereby providing teeth with the ability to flex and absorb tremendous functional loads without fracturing.
Normal dentin is composed of millions of tubules and its structure is unusual in that the number and size of its tubules changes as you move from the periphery toward the pulp chamber. Near the pulp the tubules are very close together and the water content of this deep dentin is high. Near the enamel the tubules are far apart occupying less than 1% of the surface area. The dynamics of dentin are just beginning to be understood. Dentin also gives the tooth its color and so to change the color of the tooth the color of the dentin must be changed.