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1. The Enamel
Enamel is the outer layer of the
exposed tooth. It is a very hard and thin translucent
layer of calcified substance that envelops and protects
the dentin (the main portion of the tooth structure -
see below) of the crown (4) of the tooth.
Enamel is the hardest substance in
our body and is almost entirely composed of calcium
salts. The hardness of enamel is an important property
as the main role of enamel is to protect the softer
underlying dentin of the tooth. Enamel also serves as
the surface for chewing, grinding and crushing of food
and this is another reason for its hardness.
Despite its hardness, it is NOT impervious to decay and
resistant to fracture.
Compared to any other structure in
our body, enamel has the highest concentration of
minerals (90%). The proteins in enamel are not found
elsewhere and they are called enamelins and amelogenins.
The high mineral content (mature enamel has no cells and
is not alive) makes it the hardest component and also
most resistant (but not impervious) to bacterial attack
since there is little organic matter present. A flaw of
enamels hardness though is that it is prone to chipping
and splitting, as it is a brittle substance.
2. The Dentin
Dentin is found right underneath the
enamel layer and is the most abundant dental tissue. The
dentin is the tissue which determines the size and shape
of teeth. Dentin is a bone-like substance that is formed
by odontoblast cells (bone is formed by osteoblasts),
which make up most of the structure of the tooth. 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 (3). 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.
3. The Pulp Chamber
The pulp chamber is the soft area
within the center of the tooth. The tooth's nerve lies
within root canals, which lie within the roots or "legs"
of the tooth. The root canals travel from the tip of the
tooth's root into the pulp chamber, which also contains
blood vessels and connective tissue that nourish the
tooth.
A tooth's nerve is not vitally
important to a tooth's health and function after the
tooth has emerged through the gums. Its only function is
sensory conduction, in order to provide the sensation of
hot or cold. The presence or absence of a nerve will not
affect the day-to-day functioning of the tooth.
4. Crown
The crown is the actual exposed part
of the tooth that is visible in the mouth. This is
the anatomical term in reference to the human tooth.
To confuse things even more, a crown is also the "cap"
that is sometimes placed on a tooth.
5. Root
The root portion of the tooth is the
part that is not visible (in a healthy tooth). It
is the portion of the tooth that sits in the bone and
anchors the tooth to it. Within the root travel
the root canals, which carry the nerves and blood
vessels to and from the pulp chamber.
6. Gums (Gingiva)
The gingiva is the
fibrous investing tissue, covered by epithelium which
immediately surrounds a tooth and is contiguous with its
periodontal ligament (9) and with the mucosal tissues of
the mouth. The gingiva can often become
inflamed (from excessive plaque and calculus) and this
condition is called
Gingivitis.
7.
Alveolar Bone
Alveolar bone can best be described
as a layer of compact bone that forms the socket of the
roots and surrounds the roots of all teeth. Often
this alveolar bone shrinks down the root of a tooth, so
that the tooth lost some attachment. This
condition is called
Periodontitis.
8. Root Canal
The root canal is the canal that runs
through the center of any root, carrying the nerves and
blood vessels to and from the pulp chamber and
connecting them to the big nerve and vessel canal inside
the jaw bone. Again this is an anatomical term, as
opposed to the "root canal procedure", which is a
procedure, where the nerve and blood vessels are removed
from the canal (more about this topic in the
Endodontics section).
9. Peridontal Ligament
The periodontal
ligament is a thin, fibrous
ligament that connects the tooth to the bony
socket. Normally, teeth do not
contact the bone directly;
a tooth is suspended in its socket by the fibers
of the ligament. This arrangement
allows each tooth limited
individual movement. The fibers act as shock
absorbers to cushion the force of the
chewing impact of mastication. |
