Page 122 - REMOVABLE ORTHODONTIC APPLIANCES

114 Removable Orthodontic Appliances
Adams' clasps are most commonly Repairs
constructed from 0.7 mm hard stainless-steel
wire, which is ideal for molar clasps. Adams' Appliance breakage represents an inconve-
universal pliers are well suited to this task. nience to everyone involved and, if repeated,
Alternatively, a pair of light wire pliers (such as can prolong treatment. Kerr (1984) suggests
Ormco ABZ 0411 or 6A61) may be used. The that most breakages are due to inadequacies of
stages are as follows: the acrylic or to patient carelessness. In many
instances the appliance must be returned to the
1. Define the bridge of the clasp by bending laboratory for repair, but minor repairs and
the wire to a little beyond a right angle at adjustments can, on occasion, be carried out at
each end. After the first bend is made the the chairside.
wire can be offered up to the tooth before
the second bend is made so that the arrow-
heads will be correctly situated to grip the Acrylic repair and modifications
tooth and engage undercut at the mesial
and distal corners (Figure A.l). Minor fractures to the edges of the acrylic base-
2. The ends of the wire are bent up to form the plate may be inconsequential. All that is neces-
arrowheads, which are, initially, made in the sary is to smooth the sharp edge with a suitable
same plane as the previous bends. Each polishing stone so that it is comfortable to the
arrowhead is bent in three stages. The initial tongue.
bend is made through 90° (Figure A.2). The More major acrylic fractures will require the
second bend is best made over the tips of appliance to be re-seated onto the work-model
the pliers to permit a sufficiently narrow (after this has been treated with a mould seal)
arrowhead (Figure A.3). The arrowhead before repair. The area adjacent to the break
must next be pinched up slightly so that its should be cut back and roughened so that addi-
sides are parallel (Figure A.4). tional acrylic may be added before curing and
3. The arrowheads must now be bent to an finishing. Such a repair is usually best returned
angle of around 45° to the bridge to permit to the laboratory. It may, however, be sensible
the clasp to sit correctly against the tooth to reassemble the appliance first, using a cyano-
(Figure A.5). acrylate glue, so that the fit may be checked in
4. The outer arm of the arrowhead should be the mouth. This will avoid the time and expense
grasped with the pliers about half way along involved in arranging a repair, only to discover
its length and bent through around 90° so that the appliance does not fit because it has
that the free end will rest across the embra- been out of the mouth for some time before or
sure when the clasp is correctly positioned. after the breakage.
This must be done for each side of the clasp. When an appliance incorporates a screw
The arrowheads should sit at about 45° to which has been turned it will no longer fit the
the long axis of the tooth (Figure A.6). model. In this event the screw will need to be
5. Finish off the tags. Each tag will need to be turned back to zero (and the number of turns
tailored into its embrasure so that it achieves recorded) before the appliance can be fitted to
as low a profile as possible and is not trau- the model. After repair, the screw may be re-
matized by the opposing teeth. This will opened before the appliance is refitted in the
usually entail some slight lateral adjustments mouth.
(Figure A.7). On the palatal side of the It may often be necessary to build up an
contact point the tag should pass down anterior bite plane during the course of treat-
towards the palatal papilla before being ment so that further bite opening can be
kinked slightly away from the plaster. It obtained. This is easily carried out at the chair-
should then run parallel to the plaster and side using one of the acrylics mtended for
just out of contact with it for about 1 cm. The denture relining or extension. The surface of
end should be cut off and turned down to rest the existing bite plane is roughened and the
on the model (Figure A.8). This ensures that acrylic is mixed to a wet dough. It is applied
the wire tag will later be completely evenly to the bite plane and the appliance is
surrounded by acrylic during construction. then held in tepid water for a few moments
The finished clasp is shown (Figure A.9). until the acrylic surface has 'skinned'. The