ON GUTTA-PERCHA AS A PERMANENT STOPPING. 153 



sides witliout disturbing the tooth by the exercise 

 of pressure, &c., while its being so light, and a non- 

 conductor, would probably render it more tolerable 

 to the tooth than a metallic stopping would be. 



In cases where it is exposed to mastication, it 

 will probably become countersunk or moulded into 

 a hollow on the surface after a time, but I have 

 never found it in these cases forced away from the 

 sides, showing that it must adhere well to the edges 

 and walls of the cavity. This adhesion to the tooth 

 is a point which I was at first very doubtful about, 

 and I did not anticipate that it would take place so 

 completely as I have found it to do. Theoretically 

 speaking, there should be no limit to its durability 

 where it is not exposed to mastication, and where 

 it is, it may be readily added to from time to time, 

 should it become hollow. 



In my experiments with gutta-percha I had 

 another object in view besides the stopping cement ; 

 I wished to obtain a material for artificial gum, and 

 particularly for the purpose of coating over bone 

 pieces to protect them from the chemical action of 

 the mouth ; in this case it is perhaps more essential 

 even than in that of the stopping, to get rid of the 

 natural colour of the gutta-percha, or otherwise the 

 delicate tint of the gum could by no possibility be 

 imparted to it ; but now, by a little of this silica, the 

 colour may be made as pale as we please ; and as it 

 is light, and so little of it required to produce the 



