Page 48 - REMOVABLE ORTHODONTIC APPLIANCES

40 Removable Orthodontic Appliances
Intraoral anchorage
Intramaxillary anchorage is provided from
within a single arch. This is the usual form of
anchorage utihzed in removable appliance
treatment (Figure 6.1). Intrermaxillary anchor-
age, in which one arch provides anchorage for
tooth movement in the other (Figure 6.2), is
commonly employed during functional and
fixed appliance treatment. It cannot be used
with removable appliances alone because the
elastics will tend to displace the appliances. It is
possible to use a removable appliance in one
arch (usually the lower) to provide a point of
attachment for intermaxillary elastic traction to
a fixed appliance in the opposing arch. This
would only be indicated when no active move-
Figure 6.2 In this illustration the opposing arch is
ment is needed in the lower arch.
used for anchorage. Elastics are stretched between
the upper fixed appliance and a lower removable
appliance. For this to be effective, the retention of the
Intramaxillary anchorage lower appliance must be good. Note the modification
of the molar Adams' clasp to provide a hook for the
elastic. This is an example of intermaxillary
This is provided mainly by the clasped teeth or anchorage.
those that are held in position by a short labial
bow. The baseplate, however, by its close adap-
tation to the palate and to the teeth that are not
to be moved, offers appreciable further anchor- Intermaxillary anchorage
age.
In a few situations, anchorage may be A removable appliance can be used in conjunc-
described as reciprocal (Figure 6.3). This occurs tion with a single arch fixed appliance to
when two evenly balanced groups of teeth are provide a source of anchorage from the oppos-
used to provide the anchorage for each other. ing arch. This is most common in a class II
An example would be the bilateral expansion occlusion with a well-aligned lower arch. A
of the upper arch, or closure of median lower removable appliance is required and
diastema. hooks must be incorporated in the molar clasps

Figure 6.3 An example of reciprocal
anchorage where an upper arch is being
expanded. (Note that the short 'U' loop labial
bow will require adjustment to permit
expansion to take place.)