Page 59 - REMOVABLE ORTHODONTIC APPLIANCES

Class I malocclusions 51
Retention the first premolars may have to be clasped as
Adams' clasps on 6|6; Southend clasp on 1|1. well. This means that once the second premo-
lars have been retracted sufficiently, a second
Anchorage appliance will be required to retract the first
Spring pressure must be kept light. premolars and canines.

Points to note
The buccal springs need to be adjusted care- An appliance to retract premolars
fully to avoid trauma to the cheek. Once a (Figure 7.5)
buccally positioned canine has been retracted Active components
sufficiently the spring can be modified to move Palatal finger springs 54|45.
the canine palatally.
In view of the fact that it is easy to apply Retention
excessive force with these springs a palatal Clasps on 7|7 and 1|1 (or possibly on 4|4).
cantilever spring is preferable where palatal
movement is not required. Baseplate
An anterior bite plane is indicated if the over-
bite is increased or if the occlusion would inter-
Premolars - distal movement fere with the premolar retraction.
Where first permanent molars have been Anchorage
extracted and the premolars are to be retracted, Provided by the other teeth.
a removable appliance with palatal springs is In a moderate class II case extraoral reinforce-
used. Usually, springs to retract first and second ment may be necessary. When retention is poor
premolars are included in the same appliance, this can present difficulties. Two appliances will
but they must not all be activated simultaneously be required: the first with clasps on the upper
or anchorage will be lost. The acylic should be incisors and on the first premolars carrying tubes
trimmed to allow the first premolars to follow for the facebow, and the next appliance with
the second premolars as they are retracted. tubes on the clasps on the second premolars.
Retention of the appliance may be a prob-
lem, particularly if the second permanent Points to note
molars have not erupted fully. Some retention Sometimes there is a tendency for the second
is always required anteriorly - for example a permanent molars to drift mesially in spite of
Southend clasp on the central incisors. If the the clasp. If these teeth are not fully erupted it
second permanent molars offer poor retention, may be helpful to incorporate palatal stops in

Figure 7.5 An upper removable
appliance to create space for 3|3. Palatal
finger springs (0.5 mm) to retract 54|45.
The springs should be boxed and guarded
(not shown). Adams' clasps Til and
double Adams' clasp 1|l (0.7 mm).