Lesson 1: Anatomy of Tooth Color

Dr. Lee to Mary: "Please open wide so I can have a good look at the enamel on your teeth."

Tooth enamel is the hardest substance in body. About 95% of enamel consists of calcium phosphate molecules that pack together forming highly organized apatite crystals. Apatite crystals can be hydroxyapatite, which has an attached oxygen and hydrogen group, or fluorapatite, which has a fluoride ion attached to the calcium phosphate molecule. Fluorapatite forms a stronger crystalline lattice than hydroxyapatite that is more resistant to acid attack.

This tightly packed mass of crystals forms an enamel rod, which is the basic functional unit of enamel. Enamel rods are found in rows, and within each row, the long axis of the enamel rod is perpendicular to the underlying dentin and pulp. The greatest thickness of enamel is at the crown, or biting surface.

Image: Enamel, dentin and pulp of a tooth.

Dr. Lee to Mary: "Your enamel appears thick and well-mineralized. You must be using fluoridated oral hygiene products."

Image: Dentin.

Natural tooth color comes from enamel, which is semi-translucent, and dentin, which ranges from yellowish white to grayish white.

Dr. Lee to Mary: "Flash us a smile again so we can look the thickness of your enamel on different types of teeth."

The thickness of healthy enamel varies by tooth. Enamel is thinnest on incisors (about 2 mm) and thickest on molars (2.5 to 3 mm).

Dentin is also a major contributor to overall tooth color. Genetically determined, dentin color ranges from yellowish white to grayish white.

Dentin is the largest tooth structure. It is calcified with tubules filled with plasma-like fluid, as shown here. As a living tissue, dentin conducts thermal sensitivity and pain from enamel to the nerve root, resulting in hypersensitivity when exposed through decay.