Biomedical Engineering Reference
In-Depth Information
A normal tooth can be divided into three parts: the crown, the neck and the root. The crown
is the part of the tooth that is visible above the gum (gingiva). The neck is the region of the
tooth that is at the gum line, between the root and the crown. The root is the region of the
tooth that is below the gum. Some teeth have only one root, for example, incisors and canine
(eye) teeth, whereas molars and premolars have 4 roots per tooth.
The crown of each tooth has a coating of enamel, which protects the underlying dentine.
Enamel is the hardest substance in the human body, harder even than bone. It gains its
hardness from tightly packed rows of calcium and phosphorus crystals within a protein
matrix structure. Once the enamel has been formed during tooth development, there is
little turnover of its minerals during life. Mature enamel is not considered to be a 'living'
tissue.
The major component of the inside of the tooth is dentine. This substance is slightly softer
than enamel, with a structure more like bone. It is elastic and compressible in contrast to the
brittle nature of enamel. Dentine is sensitive. It contains tiny tubules throughout its
structure that connect with the central nerve of the tooth within the pulp. Dentine is a 'live'
tissue.
Fig. 3. Internal structure of a normal tooth.
