THE TEETH. 99 



Persons who select artificial teeth of greater whiteness 

 than is ever seen in nature will perhaps be surprised to learn 

 at what cost of trouble and ingenuity varying tints are 

 imparted by the manufacturer of artificial teeth to naturally 

 white materials. Yellow tints are given by titanium; blue 

 by platinum; bright blue by cobalt; bluish yellow by tita- 

 nium and platinum mingled. It would be altogether too tech- 

 nical to particularise here the exact composition of mineral 

 teeth. The best general exposition will consist in the state- 

 ment that they are made-up of a material holding felspar, 

 borax, clay, occasionally flint-glass though that is not advis- 

 able and silica. They are moulded either in plaster-of-paris, 

 porous stone, or metal ; the last being preferable. They are 

 next burned in a furnace like any ordinary porcelain. Some- 

 times whole blocks of this latter material are moulded, gums 

 included ; but whether blocks or single teeth, the process of 

 enamelling is necessary. It closely resembles the enamelling 

 or glazing of porcelain, especially real porcelain, of which New 

 Sevres is typical, and it is conducted in the same manner as 

 the glazing of porcelain, but more delicately. If the very 

 whitest natural tooth be carefully examined, three distinct 

 shades of tint at least will be noticed upon it. First there is 

 the tint belonging to the general body of the tooth; then that 

 of the crown, or bearing-edge, or surface ; lastly, of the part 

 running into the gum. All these three tints must be imi- 

 tated and indicated by the true dental artist. Occasionally 

 entire blocks several teeth, gums and all are made in one 

 piece of this porcelain or enamel material. In this case, be- 

 sides the three tints appertaining to the teeth proper, the 

 roseate aspect of the gum must be represented. To accom- 

 plish this the colouring-matter used is gold ; to which also are 

 due the lovely red tints we admire so much in certain pieces 

 of Bohemian glass. 



On the whole, block-teeth are not to be recommended, 

 whatever the material of them may be. Far more efficient 



