Retention component of removable orthodontic appliance
The retention component maintains the appliance in the mouth, and it is generally advisable to have the clasps located to optimise retention. The following components are commonly used.
Fixation is achieved by the arrowheads, which engage about 1 mm of the mesial and distal undercuts on the tooth. This clasp is the most common means of gaining posterior retention. For molars 0.7 mm wire is used, but 0.6 mm wire is advisable for premolars and deciduous molars. The clasp is easily modified to incorporate hooks for elastics, or tubes may be soldered for extraoral anchorage. Adjustment where the wire emerges from the baseplate is necessary if the ‘flyover’ is out of contact with the marginal ridge and/or close to the arrowhead to move it towards the tooth.
This 0.7 mm clasp is recommended anteriorly with the U-loop engaging the undercut between the incisors. Pushing the loop towards the baseplate is the only adjustment usually required.
Long labial bow
This bow is constructed from 0.7 mm (0.8 mm if designed with reverse loops) wire and is useful in preventing buccal drifting of teeth during mesial or distal movement. Alternatively it may be fitted to the teeth as a retainer.
Adjustment depends on the design, but for a Ulooped bow it is usual to squeeze the legs of the U-loop, followed by an upward adjustment anteriorly to restore its optimal vertical position.