IRREGULARITIES OF THE TEETH. 24*7 



The molares of the child, on the contrary, are considerably 

 larger than the bicuspids which succeed them, and resem- 

 ble, very nearly, the permanent molares. 



" The roots of these teeth the molares of the child are 

 similar in number to those of the adult molares, but they 

 are flatter and thinner in proportion more hollowed on 

 their inner surfaces, and diverge from the neck at a more 

 abrupt angle, forming a sort of arch." 



DIFFERENCES BETWEEN THE TEETH AND BONE. 



Six points of difference exist between teeth and bone. 



1. Every tooth has its larger portion naked and exposed 

 to the air ; while bone, on the contrary, is surrounded at 

 every point by periosteum or cartilage, 



2. The structure of a tooth is more compact, has not so 

 much of the animal, but more of the mineral ingredient 

 than bone. Is also less vascular and not so highly organized. 



3. The cavity of a tooth contains a pulp, instead of the 

 medulla of bone, 



4. The diseases of teeth and their power of recovery 

 differ from bone. 



5. Their development and growth differ from bone. 

 Teeth develop themselves from the surface to the centre ; 

 bone, on the contrary, from the centre to the circumference. 

 Teeth commence by a mucous papilla or bulb, enclosed in 

 a sac, which is at first the , depressed mucous membrane, 

 forming a follicle ; and have three stages of growth, the pa- 

 pillary, follicular, and saccular, while the three stages of 

 bone are the mucous, cartilaginous, and osseous. 



6. The duration of teeth is less than that of bone, and 

 once during life they are completely renewed, entirely dis- 

 placed by a new and wholly different set, a thing unknown 

 to bone. 



IRREGULARITIES OF THE TEETH. 



Any deviation from the natural condition of the teeth, 

 whether in the time of their appearance, their number, posi- 

 tion, form, size, or intimate structure, may in the most com- 

 prehensive sense of the term, be considered an irregularity, 



