THE TEETH. 



m 



THE TEETH. 



The human subject is provided with two sets of Teeth, which make their 

 appearance at different periods of life. The first set appear in childhood, and 

 are called the temporary, deciduous, or milk teeth. The second set, which also 

 appear at an early period, continue until old age, and are named permanent. 



Fig. 385. The Permanent Teeth. External Yiew. 



Inciiort 



Wisdom toath 



Fantf 



Neck 



Crown, 



-r Jaw* 



Malar 



Canine 



The temporary teeth are twenty in number ; four incisors, two canine, and 

 four molars, in each jaw. 



The permanent teeth are thirty-two in number ; four incisors, two central 

 and two lateral, two canine, four bicuspids, and six molars, in each jaw. 



General characters. Each tooth consists of three portions; the crown or body, 

 projecting above the gum; the root, or fang, entirely concealed within the alve- 

 olus ; and the neck, the constricted portion between the other two. 



The roots of the teeth are firmly implanted within the alveoli ; these depres- 

 sions are lined with periosteum, which is reflected on to the tooth at the point 

 of the fang, and covers it as far as the neck. At the margin of the alveolus, 

 the periosteum becomes continuous with the fibrous structure of the gums. 



PERMANENT TEETH. 



The Incisors, or cutting teeth, are so named from their presenting a sharp, 

 cutting edge, adapted for cutting the food. They are eight in number, and 

 form the four front teeth in each jaw- 



The crown is directed vertically, is wedge-like in form, being bevelled at the 

 expense of its posterior surface, so as to terminate in a sharp, horizontal cut- 

 ting edge, which, before being subject to attrition, presents three small promi- 

 nent points. It is convex, smooth, and highly polished in front ; slightly 

 concave behind, where it is frequently marked by slight longitudinal furrows. 



The neck is constricted. 



The fang is long, single, conical, transversely flattened, thicker before than 

 behind, and slightly grooved on each side in the longitudinal direction. 



The incisors of the upper jaw are altogether larger and stronger than those 



