Page 111 - REMOVABLE ORTHODONTIC APPLIANCES

Retainers 103
Figure 11.1 A Hawley retainer. Adams' clasps
gig (0.7 mm) and a fitted 'U' loop labial bow
(0.7 mm).

'U' loop labial bow retainer {Hawley) Acrylic covered labial bow
The appliance generally has Adams' dasps on Labial bows have sometimes been made
the upper first molars and a 'U' loop labial bow 'fitted', i.e. with the wire shaped to fit the labial
lying against the incisors (Figure 11.1). The contour of the incisors precisely. This is now
acrylic contacts the palatal surface of the teeth more satisfactorily achieved by the addition of
all the way around the arch. When fitting this a narrow band of acrylic to the labial bow
type of retainer it is important that the labial (Figure 11.2). This modification enables a more
bow contacts the incisors - especially any accurate fit than can be achieved with a labial
aspect of an incisor that may have been bow alone and helps to ensure that corrected
displaced at the start of the treatment. The rotations are maintained. For an improved
acrylic should be in contact with the incisors aesthetic result the acrylic used can be a
unless an attempt is being made to achieve dentine shade.
slight over-correction of a pre-existing rotation.
In such a case, the acrylic may need to be
trimmed adjacent to the most displaced part of
a tooth. Begg retainer
This retainer, which was devised for the Begg
technique, avoids the need for a molar clasp by
using a continuous bow with adjustment loops
which emerges distal to the upper molars
(Figure 11.3). This appliance has the advantage
that the absence of the molar clasps permits
better settling of the occlusion but, for the same
reason, good appliance retention may be diffi-
cult to achieve.

Vacuum-formed retainers
The advent of newer materials has enabled
vacuum-formed retainers to be made. These are
inconspicuous and excellent at retaining rota-
tions or apical position of incisors. A full arch
coverage, however, prevents settling of the
Figure 11.2 A modified bow retainer. The anterior
part of the labial bow is covered in acrylic, which buccal occlusion and any closure of slight resid-
engages the embrasures between the incisors. ual extraction space. A retainer extending only