THE INCISORS. 601 



alveolar partitions. These partitions then become absorbed in such a manner 

 that at a given moment the two teeth are found to lie in contact (Fig. 275). 



There results, in ordinary cases, from the relation which is established 

 between the posterior face of the deciduous tooth and the crown of the replacing 

 tooth, a direct compression of the one upon the other, the effect of which is a 



FIG. 275. Longitudinal section of the jaws showing the relative situation of milk and perma- 

 nent incisors. 



flattening and atrophy of the root of the first dentition. The permanent teeth, 

 nevertheless, are sometimes placed at the level of the others, without compress- 

 ing or pushing from their sockets, but simply remain situated behind them. 



B. Incisors of the Second Dentition. 



These teeth, known under the name permanent or adult incisors, incisors of 

 replacement, number the same as the preceding, which they succeed. There are, 

 therefore, in each jaw two pincers, two intermediates, and two corners. 



They are distinguished particularly from the milk incisors in that they are 



