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HISTOEY OF DENTAL SURGERY 379

plied until the blank form of celluloid is plastic, then the flask is gradually
closed.
Dr. J. H. Alexander in 1875 claims to have been first to use steam to soften
celluloid, and Dr. R. F. Hunt makes the same kind of claim as to the use of
dry heat, and also to putting an apparatus on the market to work the material
in dentistry.
Celluloid came rapidly into favor and bid fair to dethrone vulcanite, but
after being worn in the mouth a very few years it loses its beautiful color.
It is not as tough and elastic as vulcanite, wears away, loses its smooth surface,
etc., so it has been abandoned.
The new mode continuous-gum was a vulcanite base faced with celluloid;
using plain teeth it is the nearest approach to porcelain that has been ob-
tained with plastics.
This same style of work can lie made with gold or cast alloy plates, but
these styles of dentures never came into general use.
Zylonite is similar to celluloid but miich better, for dental use, in color and
iranslucency, and does not scale. It is composed of pyroxylin and camphor and
it is claimed to be a chemical combination ; it is prepared in blanks and molded
the same as celluloid and was used considerably, but when the ''rubber
j)atents" expired, both celluloid and zylonite were abandoned.
Dr. Truman (of London, we believe) introduced gutta-percha into the
United States as a base for artificial teeth in 1851, and many experiments were
made with it in combination with sidphur. Combined with half its weight of
sulphur, and the compound then mixed with half its weight of vermillion there
was formed a substance called coralite which hardened under the same condi-
tions as vulcanite, but it became so brittle that its use was abandoned.
Dr. Furlong, of Cleveland, Ohio, recently applied for a patent on h\s
"Plastic Impression Riibber," of which he says : '"It is strong, durable and flex-
ible, will not scale or irritate the month. It takes as accurate an impression as
wax or modeling compound, and is used for re-fitting plates that have loos-
ened owing to the resorption of the gums or process, or for perfectlv fitting
plates that from any cause are a misfit. It is preferred for attaching teeth to
new aluminum plates owing to its wonderful clinging properties."

VnLCANITE.
Charles Goodyear discovered the remarkable effects of sulphur in combi-
nation with caoutchouc, and since 1840 or '43 this has extended its use. In
1844 a patent was granted to him for making soft or flexible rubber. Subse-