Tooth whitening the human eye and brain. Teeth are composed of a surface enamel layer, which is whiter and semitransparent, and an underlying dentin layer, which is darker and less transparent. These are calcified, hard tissues comparable to bone. The natural shade of teeth is best considered as such; an off-white, bone-color rather than pure white. Public opinion of what is normal tooth shade tends to be distorted. Portrayals of cosmetically enhanced teeth are common in the media. In one report, the most common tooth shade in the general population ranged from A1 to A3 on the VITA classical A1-D4 shade guide.
Human tooth development (0.1–0.2 μm in diameter). The odontoblasts begin to move toward the center of the tooth, forming an extension called the odontoblast process. Thus, dentin formation proceeds toward the inside of the tooth. The odontoblast process causes the secretion of hydroxyapatite crystals and mineralization of the matrix. This area of mineralization is known as mantle dentin and is a layer usually about 150 μm thick. Whereas mantle dentin forms from the preexisting ground substance of the dental papilla, primary dentin forms through a different process. Odontoblasts increase in size, eliminating the availability of any extracellular resources to contribute to an organic