Page 101 - REMOVABLE ORTHODONTIC APPLIANCES

Chairside management 93
The wrong appliance from seating properly. Such undercuts need to
be blocked out on the model before the appli-
In a busy practice or laboratory incorrect
labelling can occur. It is possible that the wrong ance is made, because subsequent trimming
appliance has been returned. may weaken the appliance unduly.
Wire loops, which lie close to the gingivae,
take no account of the path of insertion so that
Anticipation of extractions they may impinge on the mucosa as the appli-
If the technician has removed from the model ance is seated. Careful adjustment of the appli-
the teeth which are to be extracted, and the ance can usually avoid this.
appliance encroaches on this area, it will not fit
without modification until the extractions have
been carried out. The technician should be Difficulties with clasps
asked to leave all existing teeth on the model
during appliance construction, except in cases Check the design of the Adams' clasps and
where wires are to be positioned across extrac- ensure that there is adequate undercut on the
tion spaces. first molars. Overtrimming of the model during
construction can make the clasps so tight that
insertion is impossible. In adult patients, trim-
Eruption of teeth ming is usually unnecessary and even to take
the arrowheads up to the gingivae may mean
The eruption of palatally placed teeth, particu-
larly upper second premolars, can cause prob- that excessive undercut is engaged.
lems. This usually occurs when there has been a
delay in fitting the appliance since the impres-
sion was taken. Unless the embedded parts of Subsequent appliances
the wirework override the erupting teeth, the
acrylic can be trimmed away, but if the wirework Occasionally a subsequent appliance will not fit
is in the way, this provides a considerable diffi- because movement of the teeth has occurred
culty. The eruption of an instanding tooth should since the impression was taken. This may result
be anticipated when designing the appliance. because the previous appliance was left active or
because the patient has ceased to wear it. Either
of these events can cause inconvenience and the
Inadequate impression latter can even produce the situation where
An impression, which has been removed from neither the new nor the old appliance will fit.
the mouth before it is completely set, which has
come away from the tray or been allowed to dry
out, will be distorted. Any appliance made on Subsequent visits
the model from such an impression is unlikely
to fit well. Similarly, inadequately extended Successful management of orthodontic treat-
impressions or those with air blows of any size ment depends upon careful assessment at each
may present problems which the technician visit so that lack of progress or unwanted tooth
cannot overcome. movements can be recognized early and reme-
dial action is taken. The appliance must be
adjusted with care and good records need to be
Delay since the impression kept.
Forward movement of the buccal segments The patient should be seen 2 or 3 weeks after
following orthodontic extractions or natural the appliance has been fitted and then at
loss of deciduous teeth may interfere with monthly intervals. Inadequate attention to
fitting. This is very common when first molars detail at regular visits may mean that something
have been extracted. is overlooked and that progress is slow or
erratic. The acrylic or the occlusion may inter-
fere with tooth movement, unintended move-
Excessive undercut
ments may be taking place or anchorage loss
Undercuts rarely give rise to a problem in the may be occurring. Oral hygiene can also deteri-
upper arch but can prevent a lower appliance orate, unnoticed, over the course of a few visits.