Page 108 - REMOVABLE ORTHODONTIC APPLIANCES

100 Removable Orthodontic Appliances
Figure 10.18 Activation of an apron
spring. The procedure for a Roberts'
retractor is identical.

the top of the descending vertical arm and the the tooth during insertion. The provision of
spring flexed palatally (Figure 10.18). Vertical extra loops allows for further adjustment of the
adjustment is usually unnecessary but the spring as the tooth moves.
supporting arms may again need bucco-palatal 'Z' springs are useful for proclining individ-
adjustment so that trauma is avoided. ual incisors. Again, the wire is gripped in the
pliers and pulled forward and slightly upward
from the acrylic to activate it (Figure 10.19). By
Springs carrying out lingual flexing the spring in this manner the appliance
movements is self-activating as it is put into the mouth and
Buccal springs (described in Chapter 3) to
move teeth palatally can be adjusted in a simi-
lar manner to that described for buccal canine
springs. A buccal canine spring can itself be
used to push a tooth palatally, perhaps at the
end of retraction. To achieve this, the end of
the spring, which engages the tooth, is bent
through 90 degrees and the spring is adapted so
that this can rest on the buccal face of the

Springs carrying out buccal
movement
Cranked palatal finger springs can be adjusted
in the manner described for palatal finger
springs. 'T' springs are useful for pushing
premolars buccally and can be activated simply
by seizing the cross-piece of the 'T' and pulling
the spring outwards and slightly away from the
fitting surface of the acrylic so that it binds on Figure 10.19 Activation of a palatal 'Z' spring.