Fig. 48.—Temporary and Permanent Teeth together.
- Temporary teeth:
- A, central incisors;
- B lateral incisors;
- C, canines;
- D, anterior molars;
- E, posterior molars
- Permanent teeth:
- F, central incisors;
- H, lateral incisors;
- K, canines;
- L, first bicuspids;
- M, second biscuspids;
- N, first molars
The plan of a gradual succession of teeth is a beautiful provision of nature, permitting the jaws to increase in size, and preserving the relative position and regularity of the successive teeth.
Fig. 49.—Showing the Principal Organs of the Thorax and Abdomen in situ. (The principal muscles are seen on the left, and superficial veins on the right.)
135. Structure of the Teeth. If we should saw a tooth down through its center we would find in the interior a cavity. This is the pulp cavity, which is filled with the dental pulp, a delicate substance richly supplied with nerves and blood-vessels, which enter the tooth by small openings at the point of the root. The teeth are thus nourished like other parts of the body. The exposure of the delicate pulp to the air, due to the decay of the dentine, gives rise to the pain of toothache.
Surrounding the cavity on all sides is the hard substance known as the dentine, or tooth ivory. Outside the dentine of the root is a substance closely resembling bone, called cement. In fact, it is true bone, but lacks the Haversian canals. The root is held in its socket by a dense fibrous membrane which surrounds the cement as the periosteum does bone.