THE MOUTH, ORAL OR BUCCAL CAVITY 



1207 



it as far as the neck. This is the root-, or pericemental membrane {periosteum alve- 

 olare}. At the margin of the alveolus the periosteum becomes continuous with 

 the fibrous structure of the gums. 



Surfaces. In consequence of the curve of the dental arch, such terms as anterior, 

 posterior, internal, and external, as applied to the teeth, are misleading and con- 

 fusing. Special terms are therefore applied to the different surfaces of a tooth : 

 That which looks toward the lips and cheek is the labial or buccal surface (Jades 



Right upper. 



FIG. 916. Deciduous teeth of left side. Labial view. 



FIG. 917. Deciduous teeth. Lingual view. 



labialis); that toward the tongue is the lingual surface (fades lingualis); that 

 surface which is directed toward the mesal plane, supposing the teeth were arranged 

 in a straight line outward from the central incisor, is known as the proximal 

 surface, looks toward predecessor; while that directed away from the mesal plane 

 is called the distal surface, looks toward successor. The surface which comes in 

 contact with the teeth of the opposite jaw is the grinding, masticating, or occlusal 

 surface (fades masticator ia). 



FIG. 918. Permanent teeth, right side. (Burchard.) 



The Temporary, Deciduous, or Milk Teeth (denies decidui) (Figs. 916 and 917) 

 are smaller, but resemble in form those of the permanent set. The neck is more 

 marked, owing to the greater degree of convexity of the labial and lingual surfaces 

 of the crown. The last of the two temporary molars is the largest of all the 

 deciduous teeth, and is succeeded by the second bicuspid. The first upper molar 

 has only three cusps two labial, one lingual; the second upper molar has four 

 cusps. The first lower molar has four cusps; the second lower molar has five. 



