Page 76 - REMOVABLE ORTHODONTIC APPLIANCES

68 Removable Orthodontic Appliances
Treatment methods is best made in 0.5 mm stainless steel wire. First
molar clasps are required for retention,
As has already been slated, the two main together with a clasp on the incisors. Overbite
avenues of treatment are hkely to involve reduction is produced by a flat anterior bite
either premolar extractions or second molar plate, which is just sufficiently deep to contact
extractions. Premolar extraction cases consti- the lower incisors evenly (Figure 8.7). Where
tute by far the larger group and will be extraoral support is required, tubes should be
described first. added to the molar clasps to accept the face-
bow.
Where an upper canine is crowded buccally a
Premolar extraction cases standard palatal finger spring is unsuitable. In
such cases a supported buccal canine retractor
The upper canines require retraction into a in 0.5 mm wire is recommended - although this
class I relationship with the lowers when the is, in many ways, less satisfactory. Overbite
latter are in an uncrowded position. Any neces- reduction and extraoral support may be
sary overbite reduction can be achieved at the achieved as described above.
same time with an anterior bite plane. A second
appliance is then required to reduce the over-
jet, while maintaining overbite reduction with 2. Overjet reduction
an anterior bite plane and holding the canines Once the canines have been retracted into class
in their new position. I with the lowers and the overbite has been
reduced, overjet reduction can commence,
using a Roberts' retractor. The appliance
Appliance design
should incorporate stops mesial to the canines
Appliances are required for the three distinct (to prevent their forward relapse) and an ante-
stages and will be described below. rior bite plate sufficiently thick to maintain the
existing overbite reduction. In order to permit
overjet reduction the acrylic must be hollowed
1. Canine retraction and overbite
reduction out on the palatal aspect of the fitting surface.
This should be carried out progressively during
The ideal spring for canine retraction is the overjet reduction (Figure 8.8). Towards the end
palatal finger spring, boxed and guarded. This of this process the canine stops can be removed

Figure 8.7 (a) An appliance with palatal canine retractors (0.5 mm) and a double Adams' clasp on 1|1
{0.7 mm), (b) The upper bite plane should only extend sufficiently posteriorly just to engage the lower incisors.