Page 42 - REMOVABLE ORTHODONTIC APPLIANCES

34 Removable Orthodontic Appliances
Adams' clasps on the upper first molars may
give adequate retention, but for an active appli-
ance three or four point retention is generally
advisable (Muir, 1971). During canine retrac-
tion, for example, a Southend clasp on the
upper central incisors may supplement the
molar clasps to give good retention. Where a
Figure 4.11 A fitted labial bow (0.7 mm wire). molar is being moved distally with a screw, or
where an incisor is being proclined, additional
clasps on one or both first premolars may offer
proclined, a labial bow fitted to the incisor third a way of producing excellent retention. Reten-
of the crowns may give an easier path of inser- tion need not be symmetrical but can be tailored
tion of the appliance. to suit the task of the particular appliance.

Planning retention References
The positioning of retentive components is Adams. C.P. (1955) The design and construction of remov-
important and must be planned for each indi- able orthodontic appliances. John Wright and Sons Ltd,
vidual appliance, taking into account the forces Bristol
that will tend to produce displacement. It is Bell, C. (1983) A modified lower removable appliance
using lingual clasping and soft tissue anchorage. British
unwise to attempt to clasp every available tooth
Journal of Orthodontics, 10: 162-163
because this may make the appliance difficult Muir, J.D. (1971) Anterior retention in the removable
for the patient to manage - as well as making appliance. Transactions of the BSSO. 57:178-184
adjustment complicated and interfering with Stephens, C D . (1979) The Southend clasp. British Journal
tooth movement. For a simple 'retainer', of Orthodontics, 6:183-184