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154 MECHANICAL DENTISTRY AND METALLURGY.
time considerably straightened. After which it was re-
tained by the retainer shown in Fig. 114.
Rotation by Spring Bar.—Where the mesial angles pro-
trude double rotation can be accomplished by the very
simple and effectual method.
Upon each of the teeth to be rotated place bands with
tubes soldered to their labial faces near the distal angles.
One tube is set vertically and the other horizontally. A
short piece of piano or German silver wire, bent to a right
angle at one end, is inserted in these tubes, and rotation is
effected by the elasticity of the wire (Fig. 115). Once in
position, the teeth are retained by inserting- in the tubes a
suitably shaped piece of non-elastic gold wire.

Fig. 115. Fig. 116.

Another Method of effecting double rotation, recom-
mended by Dr. Angle, is shown in Fig. 116. This is a
combination appliance, consisting of bands with spurs sol-
dered to their mesio-labial angles to engage a wire ligature,
as shown in the illustration. After the bands have been
securely cemented in position a piece of rubber is stretched
between them, and the wire ligature is applied and tightly
drawn and the ends twisted together. By the occasional
renewal of this wire a powerful force is exerted which will
readily turn the teeth. After the teeth have been brought
to the desired position a temporary retention is effected by
the application of a fresh ligature and dispensing with the
rubber.
Lack of Anterior Occlusion.—This form of irregularity
is fortunately rare, as it is one of the least amenable to treat-