Page 77 - REMOVABLE ORTHODONTIC APPLIANCES

Class II malocclusions 69
Figure 8.8 (a) A Roberts' retractor (0.5 mm in
0.5 mm ID tubing), (b) The overbite should be fully
reduced before overjet reduction is commenced. The
fit surface of the bite plate should be trimmed
progressively, ensuring that the overbite reduction is
held while making space for the upper incisors to be
retracted. The anterior border of the bite plane
should be kept in a smooth curve.

as the upper incisors are retracted into contact retracted. At that stage these springs can be
with the lower. Extraoral support will some- made passive and the reverse loop labial bow
times still be necessary during this phase of can be activated. Because these bows are
treatment. extremely inflexible, many operators prefer to
In a few mild cases it is possible to correct the divide the bow at the mid-line to make it more
canines and the incisors with a single appliance. flexible to carry out overjet reduction.
The design might include palatal canine springs This approach is only indicated where there
and a reverse loop labial bow (Figure 8.9). Care is a very small overjet or where mild crowding
must be taken to activate only the palatal of the incisors exists and a reverse labial bow is
springs until the canines are sufficiently suitable for alignment.

Figure 8.9 A single appliance used for
canine retraction and reduction of a small
overjet. Canine spring (0.5 mm), reverse
loop labial bow (0.7 mm). The canine
retraction must be completed first and it
is sometimes advantageous to cold cure
the canine springs in a passive position
once the canines have been retracted.
The reverse loop labial bow may then be
activated to reduce the overjet.