Page 41 - REMOVABLE ORTHODONTIC APPLIANCES

Appliance retention 33

Figure 4.6 A double Adams' clasp (0.7 mm wire).
The position of the arrowheads is determined by the
depth of the undercuts. Frequently the arrowheads
do not need to reach the gingival margin.

Figure 4.8 A ball ended clasp between the lower
incisors engaging the embrasure undercut. A
recurved clasp is shown on the lower canine.

Figure 4.7 A modified double Adams' incisor clasp
with the bridge adapted to the labial surfaces of the
central incisors.

Figure 4.9 The Southend clasp (0.7 mm wire).
The ball-ended clasp
This uses the undercut provided by the embra-
sure and provides effective retention. The use
of the embrasure is not generally desirable The fitted labial bow
because of the danger of gingival damage and
tooth separation, but the clasp may occasion- This offers good retention on proclined upper
ally be of use when deciduous teeth must be incisors but it is less satisfactory on upright
used for retention (Figure 4.8). teeth. A short bow can fit over both central
incisors (Figure 4.10), but more commonly the
bow fits over the central and lateral incisors
(Figure 4.11). Where the incisors are very
The recurved clasp
This simple clasp uses the same undercuts, as
does the Adams' clasp. It is simpler to construct
but less effective than the latter and does not
allow the attachment of auxiliary components
such as headgear tubes (Figure 4.8).

The Southend clasp
The Southend clasp is easy to construct, unob-
trusive and well tolerated. The wire passes
round the gingival margin of the central
incisors and engages undercut between the
incisors (Stephens, 1979). It is the preferred
anterior clasp, particularly if the incisors are
proclined and can be modified to fit between a Figure 4.10 A short fitted labial bow on upper
central and lateral incisor. Breakage is rela- central incisors (0.7 mm wire). This design permits
some drifting of the lateral incisors as the canines
tively uncommon (Figure 4.9). are retracted.