931H
Fig. 14.14 (a) Simple upper removable appliance maintaining space following
extraction of 4|4 while 3|3 erupt. (b) Lower lingual arch serving as a space maintainer.
14.4.5 Digit-sucking habits
Thumb- and finger-sucking habits which persist into the mixed dentition may cause:
anterior open bite; increased overjet; unilateral posterior cross-bite with displacement.
A unilateral posterior cross-bite can occur because during digit sucking the tongue
position is low, allowing activity of the buccal musculature to narrow the upper arch
slightly (see 932HSection 14.4.2).
Although a few children continue the habit into their teenage years, nearly all grow
out of it by about 10 years of age. An anterior open bite caused by a sucking habit
(933HFig. 14.15 (a)) will usually then resolve, but it may persist and require treatment if
the tongue has adapted to the open bite by contacting the lower lip to make an anterior
seal during swallowing. Correction of an increased overjet or a posterior cross-bite
will need active treatment, and in most cases the presence of an appliance in the
mouth finally breaks the habit. For these reasons a sucking habit in a young child is
rarely a cause for concern, and parents can be reassured that drastic measures to stop
the habit are unnecessary.
'Habit-breaking' appliances are thus rarely indicated and do not always work, but they
may be considered if the effect on the occlusion is severe or if the habit is unusually
persistent (934HFig. 14.15 (b)). There are many designs of habit-breakers, some quite
barbaric, but a common one is an upper removable appliance with a steeply inclined
anterior bite plane (935HFig. 14.16 (a)-(c)). The mid-line split in the acrylic of an
expansion appliance may also help by breaking the suction.