Tooth Anatomy “part 1”

download videos of tooth anatomy.

Download tooth anatomy PDF with less details.

 Crown:

    the top part of the tooth, and the only part you can normally see. The shape of the crown determines the tooth's function. For example, front teeth are sharp and chisel-shaped for cutting, while molars have flat surfaces for grinding.

Root:

    the part of the tooth that is embedded in bone. The root makes up about two-thirds of the tooth and holds the tooth in place.

Enamel

the outermost layer of the tooth. Enamel is the hardest, most mineralized tissue in the body.yet it can be damaged by decay if teeth are not cared for properly.

Enamel is the substance that covers the crown of the tooth.  It is very hard and quite resistant to mechanical and chemical attack.  Its purpose, of course, is to protect the tooth from the dangers posed to the teeth by the oral environment.   In general, it is vulnerable only to acid attack from excess sugar decay, generalized trauma such as a blow from a hard object, and serious bruxing with associated attrition. It is white, but somewhat translucent and allows the color of the underlying dentin to shine through to a certain extent which is why teeth look yellow. In the diagram to the left, the enamel is represented by the top layer on the tooth.  Here it looks a bit like a neat haircut.  The reason it is drawn that way is because the enamel is made up of microscopic enamel rods all of which run about parallel to each other and which project  perpendicularly from the surface of the underlying dentin.  When you are looking at a tooth in the mouth, you are seeing millions of these little enamel rods packed side by side, but you are seeing them end-on, as in the illustration on the right which is a reasonable representation of their cross section.They are packed together a bit like an Escher drawing.

Dentin

the layer of the tooth under the enamel. If decay is able to progress its way through the enamel, it next attacks the dentin . where millions of tiny tubes lead directly to the dental pulp.

Dentin is the hard, yellow bone-like material that underlies the enamel and surrounds the entire nerve.  It composes the bulk of the tooth, and is sensitive to touch and other stimuli.  In the image at the top of this page, the illustration shows thousands of tiny little lines that run approximately parallel to each other and perpendicular to the surface of the nerve space.  These lines represent tiny tubes that run parallel to one another throughout the structure of the dentin.  These are called dentinal tubules, and they originate from the inner surface of the nerve space and travel perpendicularly from their point of origin to the surface of the tooth terminating at the undersurface of the enamel, or the surface of the root itself in areas where it is not covered with enamel.

The tubules contain tiny projections of cells that line the inside of the nerve space.  These cells are called odontoblasts, and they are actually the covering layer of the nerve itself.  The projections of the odontoblasts into the dentinal tubules are not nerves.  However, the odontoblasts connect with nerve axons in the dental pulp (nerve).   Exposed dentin is sensitive to touch, air and other stimuli because these stimuli cause movement of the fluid in the odontoblast projections inside the tubules.  This movement of fluid can be sensed by nerve endings in the dental pulp which anastomose (connect) with the odontoblasts.  The image on the right above is an electron micrograph of actual dentinal tubules seen end-on.

pulp:

the soft tissue found in the center of all teeth, where the nerve tissue and blood vessels are. If tooth decay reaches the pulp, you usually feel pain.

hat the lay public calls the nerve of a tooth is called the dental pulp by dentists.  It is a complex organ composed of connective tissue, blood vessels, and nerve axons.  It is pink and soft, and looks just like the lining of the mouth when it is removed during root canal procedures.  Its original purpose during development is the formation the teeth themselves.  In other words, the nerve of a tooth is a "generative" organ.  The nerve starts out as a clump of specialized cells, and as we begin to grow, it slowly takes the shape of a tooth.  The cells on the outside of the pulp begin to form the various hard structures , enamel and dentin, that we associate with the tooth itself.  The tooth is formed from the outside toward the inside, with the dental pulp slowly replacing itself with tooth structure.  While we are still young, the nerves in our teeth are relatively large, but they slowly shrink becoming more and more narrow throughout our lives.   Once the tooth is fully formed, the nerve slows its formative functions, but it keeps building dentin in a process called dentinogenesis.  During this slow growth phase of its life, the nerve serves mostly to keep the teeth hydrated and allows the dentin to retain a certain amount of elasticity.  Thus, living dentin acts something like a shock absorber, preventing the teeth from fracturing.   Whenever a nerve in a tooth dies, the tooth looses this shock absorber effect and is more prone to fracture.  This is the reason that a tooth that has been endodentically treated  needs to be protected with a crown.