WEARING AWAY OF THE CRO\yyS. 101 



comers are as large at the gums as at tlieir free extremities, and 

 notches re-appear on the superior corner teeth. 



At ticelve years^ all of the teeth are round ; only a trace 

 of the cups remains in the inferior ones. The superior corners 

 are leveled. Both incisive arclies are much narrower and the 

 tongue shows over their borders. The inferior border of the 

 jaw-bone becomes sharp, and a flattening of the sides of the 

 face, over the roots of the superior molars, is seen. The inci- 

 dence of the incisive arches increases, especially if the teeth are 

 unusually long. 



At thirteen years^ the signs of twelve years are more 

 marked. The notch on the superior corner teeth is greater. 

 The cups usually disappear from the inferior incisors at this 

 age, and the superior pinchers become round. 



At fourteen years^ the pinchers become triangular ; the 

 incisive arch is depressed in front and becomes decidedly 

 narrower. 



At fifteen years, the intermediate teeth commence to 

 become triangular. The dental star is round in all the lower 

 teeth and is dark and distinct. The cups of the upper teeth 

 are smaller in size. 



At sixteen years, the intermediate teeth are triangular. 



At seventeen years, all of the lower teeth are triangular, 

 and the dental stars are small and round. The cups of the 

 upper corner teeth have disappeared and those of the others 

 are round. 



After nineteen, the cups have usually all disappeared, the 

 teeth approach a line parallel to the bones of the jaw, which is 

 especially marked in the lower jaw, and the arches are flattened 

 from side to side. The lower teeth may be worn almost to the 

 gums, and deposits of cement around their roots may develop 

 to supply a wearing surface. 



