Page 157 - My FlipBook

CORRECTION OF DENTAL IRREGULARITIES. 145

attached. The screw-ljar is prcn'ided with a nut, which,
after the crowns have been securely set witli cement, is
turned up on the bar until moderate pressure is exerted.
This nut is then given two or three turns, three or four
times a week, according to the case in hand. The apphance
in position is shown in Fig. 103.
When it is desirable to expand the low^er maxilla, con-
tinuous crowns are made as has been directed, but to each
of these an open cylinder is soldered to the lingual surface.
Fig. 103.

This is done by fitting and soldering a gold tube over a piece
of piano-wire of the same size as the wire which is to exer-
cise the traction. After this is done, the gold tube is cut
in its long axis, by which we get the open cylinders. The
posterior ends of these tubes are closed so as to receive the
ends of the traction wdre when in position. When the
crowms are secured in position wnth cement, a piece of piano-
wire, previously shaped from the cast or die, is sprung into
the open tubes. To exercise the necessary traction, the
wire must be slightly spread before placing it in the mouth.