Page 67 - REMOVABLE ORTHODONTIC APPLIANCES

Class I malocclusions 59
and will, because this tooth is commonly must handle it with care. A lingual bar rather
outstanding, assist in moving it into line. than acrylic in the incisor region may be
stronger and more comfortable for the patient.
The appliance will have to be trimmed lingual
Examples of design: retraction of to the canines and so the baseplate should be
lower canines made thicker in these areas (Figure 7.16).

Distal movement of lower canines is required Anchorage
where there is anterior crowding. Space is This is provided by the clasped teeth and by the
usually provided by extraction of first premo- teeth and alveolar process that are contacted by
lars. Provided that the extractions are carried the appliance. It is very difficult to supplement
out in the developing dentition, preferably anchorage in the lower arch when removable
before the canines have reached the occlusal appliances are used. This makes it all the more
level, they will usually drop back into the line of important that light forces are used to retract
the arch, allowing spontaneous alignment of the canines.
the incisors. Occasionally, this may not occur,
particularly when the occlusion prevents the Points to note
canine from improving and active retraction If there is occlusal interference with the retrac-
with a removable appliance will be necessary. tion of the canines, an upper appliance with an
anterior bite plane is the most convenient way
of clearing the occlusion. If upper arch treat-
An appliance to retract lower canines ment is not required, thin molar capping may
(Figure 7.14)
be included in the lower appliance and may add
Active component to its stability and comfort.
A buccal spring in 0.7 mm wire.

Retention Distal movement of lower molars
Clasps on 6l6. Some operators also use a labial
bow but this adds little to retention and may Where early loss of deciduous teeth has
interfere with spontaneous alignment of the allowed a first permanent molar to drift
incisors during canine retraction. forwards, encroaching on space for the second
premolar, it may be necessary to move the first
Baseplate molar distally. This should be done only in an
The baseplate must be thin enough for comfort otherwise uncrowded arch. The tooth move-
but thick enough for strength. A lower remov- ment should be completed, if at all possible,
able appliance is always weak and the patient before the lower second permanent molar has

Figure 7.16 The acrylic lingual to lower right
canine is too thin. Note how the acrylic is
correctly made thicker on the left.