Human teeth are formed in the following way. In the early embryo the skin along the future line of the jaw-bones thickens and is known as the dental lamina. The edge of this extends into the tissues of the jaw and forms bud-like thickenings at intervals along the jaw. There are, at first, ten of these thickenings in each jaw. They are the "buds" of the first set of teeth.
The dental lamina later extends beyond the last deciduous tooth bud and slowly forms the buds of the permanent molars. When the embryo is about three months old the dental lamina forms further tooth buds on the inside of the developing milk teeth. These are the buds of the permanent teeth. They develop in the same way as the milk teeth but much more slowly.
The epithelial tissues of the tooth buds grow inward and form a bell-shaped structure in which a group of cells shows up densely and is termed the enamel knot. Under this knot, cells of the connective tissue become dense, forming the beginnings of the tooth body, the tooth papilla.
The cells of the papilla grow and multiply and push up under the enamel knot, forming a simple tooth-shaped structure. The cells of the enamel knot get larger and begin to produce enamel while some cells of the papilla start to release dentine. For the laying down of good hard material and its impregnation with calcium and other minerals, salts and vitamins – especially vitamin D – are needed in the blood. The hard layers are first deposited at about 20 weeks old by which time the bone of the jaws has started to form as a cup surrounding the developing teeth. More enamel and dentine are produced until the crown of the tooth is complete. The time required depends on upon the type of tooth but when the crown is complete the tooth erupts (i.e. breaks through the gum surface) by growth of the root. The latter continues to grow for a while until it is completely enveloped in the jawbone which has grown up around it. Cement is produced by the tissues of the papilla when the root begins to grow. When the root is fully formed the opening of the pulp cavity closes so that very little nutrient transfer can occur. Growth then ceases although the tissues still receive enough nourishment to stay alive.
The permanent teeth continue to develop slowly under the milk teeth. When the crown of the permanent tooth is fully formed, its root begins to grow. This causes an increase in pressure on the base of the milk tooth. The result is that the periodontal membrane and the cement and even part of the milk tooth root are broken down by enzymes and by special scavenging cells, called macrophages, which absorb the material in the manner of a feeding amoeba. When the cement and the membrane have gone there is no firm attachment of the tooth to the jaw – the tooth in fact becomes loose and eventually falls out, leaving a clear path for the permanent tooth which now rapidly grows up through the gum to take its place in the adult tooth row. When it has reached full size and is firmly embedded in its socket, the tooth ceases to grow because the opening of the pulp cavity closes just as in the milk teeth.
The gum is a mass of dense, fibrous tissue attached to the jaw bones. It is continuous with the periodontal membrane of the tooth socket which it supplies with food and oxygen via its rich blood supply.
Wisdom teeth generally grow in around 18, but some people get them later. They are permanent teeth, so if they grow in without complications, you don't lose them, unless it is to decay. But, many people have to have them pulled out because they are impacted. That means they are growing in sideways or growing into other teeth (or will). Often, wisdom teeth are shorter than other teeth because they don't develop as well, so they may need removed for that reason, also. If you get your teeth pulled, be sure to go to a Biologic dentist so you don't get a cavitation.
Structure Of A Tooth click here and below are the descriptions of the pic: http://i14.tinypic.com/29ehe8y.gif
A. tooth crown
B. neck of a tooth
C. root of a tooth
f. Pulp Chamber
g. Gingival Crevice or Sulcus
i. Gum attachment to tooth (1)
j. Periodontal fibres (2)
k. Cementum (3)
l. Bone/alveolus (4)
m. 1+2+3+4= Periodontium
n. Root canal
· 1 decade ago