Page 31 - REMOVABLE ORTHODONTIC APPLIANCES

Active components 23
tubing. It is more than twice as flexible as the Soldered auxiliary spring
standard retractor, because the shorter free
length of wire is more than compensated for by It is possible to solder a spring to the bridge of
the reduction in diameter. The tubing imparts the Adams' clasp on a first molar (0.6 mm. wire
excellent vertical stability. Although not as or 0.7 mm wire). Two versions are available.
flexible as a palatal finger spring, the The spring can be used to tuck an outstanding
supported buccal refractor has good mechani- canine or premolar into line during the final
cal properties and is easy to use, provided that stages of treatment (Figure 3.18).
care has been taken to follow the design
details.
Advantages
The spring does not cross the embrasure and so
Adjustment does not compete with other wirework. (As a
An activation of 2 mm (about one-quarter of general principle it is sensible to avoid taking
the canine width) is appropriate. It is most two wires through a single embrasure.) The
important not to bend the wire where it spring can be added easily to an existing appli-
emerges from the tubing, otherwise it may frac- ance and, if necessary, may be cranked to
ture at this site of stress concentration. The correct an outstanding canine through the loop
adjustment should be made as described for the of the labial bow on a retainer. The length - and
self-supporting buccal retractor. hence the flexibility of the spring - can be
controlled by the choice of an appropriate wire
size and where necessary by bringing the wire
from the distal end of the bridge of the clasp
Reverse loop buccal retractor
and recurving it forwards (Figure 3.18). (This
This buccal retractor is favoured by some, may be particularly useful when a second
particularly where the sulcus is shallow, as in premolar has to be moved palatally.)
the lower arch (Figure 3.17). Its flexibility
depends on the height of the vertical loop,
which should be as long as possible. The main
problem with this spring is that it is stiff in the
horizontal plane yet very unstable vertically.
For this reason, in the upper arch, we prefer
one of the other buccal retractors.

Figure 3.18 A soldered auxiliary spring (0.7 mm
wire), (a) To move a canine palatally. (b) A re-curved
spring to move a premolar palatally.
Figure 3.17 A reverse loop buccal canine retractor,
0.7 mm wire.
Disadvantages
A certain level of expertise with solder is
Adjustment
required if the spring is to be attached satisfac-
The spring should be activated by not more torily without annealing the wire of the clasp.
than 1 mm. This is most readily done by cutting When the clasp is adjusted the spring position
off 1 mm of wire from the free end and re-form- is also affected and may require compensatory
ing it to engage the mesial surface of the tooth. adjustment. It is also difficult to add this spring
Alternatively, it can be activated by opening to a clasp that is already carrying a soldered
the loop by 1 mm. tube for the application of a facebow.