

THE TEETH 135 



THE TEETH 



A human tooth is a calcareous structure of extreme hardness, 

 and is divided into an exposed crown, a constricted neck, and one 

 or more concealed roots the latter being inserted into an alveolus, 

 by means of which the whole is very firmly connected with the 

 maxillary bone. 



The central portion presents an elongated cavity (pulp -cham- 

 ber) containing vascular, nervous, and connective tissue elements 

 the pulp. 



The pulp -cavity is surrounded by the dentine, which consti- 

 tutes the major portion of the tooth 



The crown portion of the dentine is provided with a covering 

 of enamel, while the root is invested with an osseous cementum, 

 or crusta petrosa. 



A thin membrane, 1 /* or less in thickness called the membrane 

 of Nasmyth or the cuticula covers the enamel in early life, while 

 the cementum receives a periosteal investiture. The vascular and 

 nervous elements of the pulp obtain admission to the pulp -cavity 

 by a perforation or foramen at the apex of the root. 



The Pulp. The ground -substance, or stroma of the pulp, is a 

 form of primitive connective tissue, gelatinous rather than mark- 

 edly fibrous. It contains elongated capillary loops, multipolar 

 cells, and medullated and non-medullated terminal nerve -fibrils. 



Surrounding the pulp mass, and next to the dentinal wall of 

 the chamber, we find a single layer of elongated cells odontoblasts. 

 These are probably in communication, by means of processes or 

 prolongations, with fibrous elements of the pulp. 



Dentine. The dentinal stroma or matrix is made of fibrous 

 tissue containing calcium salts, and is, next to the enamel, the 

 hardest tissue of the body. The matrix is pierced with the denti- 

 nal canals (extremely minute channels, only 5/* in diameter), 

 which radiate from their beginning, next the pulp -chamber, 

 toward the outer portion of the dentine. These canals branch 

 and anastomose, and are lined with an exceedingly thin den- 

 tinal sheath. 



From the outer extremity of the odontoblasts of the pulp nu- 

 merous prolongations are sent which are probably continued within 

 the dentinal canals as the dentinal fibers. The dentinal canals 

 terminate exteriorly, by very fine lumina, in a system of irregu- 



