appliance part-time for a few days. Severe inflammation palatal to the upper incisors
can occur during overjet reduction, due to compression of the tissues between the
acrylic and the teeth (988HFig. 14.32 (a) and (b)). This should be avoided by keeping the
appliance under frequent review, and ensuring at each visit that enough palatal acrylic
has been trimmed away to allow tooth movement.
989H
Fig. 14.32 (a) Upper removable
appliance for retraction of the upper
incisors. (b) Severe gingival inflammation
resulting from compression of the
gingival tissues under the appliance
during incisor retraction.14.8.3 Root resorption
Most orthodontic treatments probably cause some resorption of root apices. In most
cases it is slight, but significant apical resorption does occur in a few patients (990HFig.
14.33 and 991HFig. 11.11). Any tooth can be affected, although studies have focused on
the maxillary incisors. The aetiology is multifactorial and individual susceptibility to
resorption is very variable, but factors associated with increased risk include:
(1) history of trauma to maxillary incisors;
(2) signs of pre-existing resorption: short roots or blunted apices;
(3) thin, pipette-shaped root apices;
(4) prolonged use of fixed appliances, especially intermaxillary elastics;
(5) intrusive forces and torquing of apices;
(6) reduction of large overjets, other than with functional appliances;
(7) treatment to align impacted maxillary canines.
Orthodontic treatment for patients in the first three categories should be as short and
simple as possible, keeping fixed appliances to a minimum and ensuring that forces