[Dental pamphlets] [No. 13]

INISTRUCTIONS.
1. Grinding and carranging.-This is done in the same manner as for rubber work. Gum or plain teeth may be used, as desired.
Finish up the wax carefully, and do not make it too thick and bulky
in any part, particularly ona the roof of the mouth. Put plenty of
wax over the pins, to allow for finishing. Do not expect a good fit
without a good impression.
2. Investing.-Have your plaster as thick as possible, and use
care to avoid bubbles. Part the flasks at the upper edge of the wax
in all cases, except where there is a coniderable undercut to the " nose" of the
cast, in which case do not trim so close
Qi to the upper edge of the wax. In such
cases too, cut off the heels of the cast
well, before flasking, so that it will
stand in the position indicated in the
S annexed cut. The pressure will thus
be brought into a direct line with the
plaster, and danger of fracture be avoided. After opening and re11moving the wax (which should be done thoroughly), the cast and
matrix should he well rubbed with powdered soap stone (obtainable
at any shoe store), which will keep the plaster from adhering to the
plate. The model may be covered with tin foil for the same purpose. Cut a groove or gutter for the surplus, around the outside of
the flask, not less than one-quarter of an inch from the model, and
entirely in the half of the flask containing the model; otherwise thin
edges of plaster are liable to break off, during the molding process,
and mix with the celluloid, or make a porous spot in the plate for
want of "back pressure." Do not cut cross gates connecting the
gutter with the mold, or if any, have themn not over one-sixteenth of