Page 40 - REMOVABLE ORTHODONTIC APPLIANCES

32 Removable Orthodontic Appliances
Limitations
The Adams' clasp has few hmitations but, if it is
not skilfully made and adjusted, the wire may
become excessively work-hardened and will be
liable to fracture. Fracture at the arrowhead can
sometimes be repaired by soldering. The other
common site of fracture is where the wire passes Figure 4.4 The Jackson clasp (0.7 mm wire) on an
across the occlusion and, should this occur, it is upper first molar. A recurved clasp used on a canine
best to replace the clasp. Some patients find the (0.6 mm wire).
bridge irritating, particularly if it is too promi-
nent. This most often happens where tubes for
headgear are soldered to molar clasps.
Anterior retention
The Jackson clasp The Adams' clasp
The Jackson clasp passes around the gingival The Adams' clasp can be used to provide reten-
margin of the molar (Figure 4.4). It may be tion at the front of the arch and commonly a
conveniently used for deciduous molars using double clasp is used spanning both central
0.6 mm wire. incisors (Figure 4.6). Alternatively, a clasp may
be used on a single incisor. The Adams' clasp is
most suited to situations where the central
Buccal acrylic lower appliances
incisors are upright or only mildly proclined.
To overcome the problem of limited undercut When there is no anterior spacing, the arm of
on the buccal aspect of lower molars, appliances the clasp will pass over the top of the embra-
have been described with clasping on the lingual sure between the central and lateral incisors.
aspect of the molars (Bell, 1983). Two acrylic The clasp is prone to breakage where it crosses
baseplates are used, one on each side resting on the embrasure.
the buccal mucosa. The acrylic is connected A double incisor clasp can be uncomfortable
across the anterior labial mucosa by a stainless for the patient and where the incisors are very
steel bar. A modified Jackson clasp is used on proclined the clasp has to be placed fairly close
the lingual aspect engaging the lingual under- to the incisor edge to avoid an excessive under-
cuts of the molars (Figure 4.5). The main use of cut. It is possible to modify the clasp by curving
such an appliance is to retract mesially inclined the bridge and flattening the arrowhead so it is
lower canines. less prominent (Figure 4.7).

Figure 4.5 A lower appliance with
buccal acrylic and lingually placed molar
clasps. The buccal acrylic is connected
anteriorly by a stainless steel bar.