CANINE IMPACTION: HOW EFFECTIVE IS EARLY PREVENTION? AN AUDIT OF TREATED CASES
Male
Figure 1. A nine year old boy with an impacted
upper right lateral treated by Orthotropics. His
maxilla was expanded and the upper incisors
proclined to a pre-determined position related
to the cranial vault and his lower incisors
protruded to their ‘correct’ relationship with the
mandibular corpus. Following the loss of the
deciduous teeth a stage 3 appliance (Fig. 2) was
used to close the anterior open bite leaving the
permanent teeth in near ideal positions.
Bishara9 suggested a figure of between 1 and 3%
but provided no supporting evidence for this.
In more recent years the suggested percentage
has risen following some larger surveys. In 2004,
Aydin and his colleagues10 prospectively reviewed
4500 consecutive panoramic radiographs within
a Turkish population. They found the incidence
of canine impaction to be 3.58%. However in
2008 Prskalo (11) found an even higher incidence
in Croatia of 4.71% within a study population of
170. It is possible that these rising figures are a
reflection of a general increase in malocclusion
reported around the world.
Early prevention is rarely recommended, possibly
because of the uncertain aetiology. Although early
extraction of the deciduous canines has been
popular for many years12 quite a high proportion of
the canines fail to erupt following this procedure,
although it does seem more successful in younger
patients.13 It would certainly be a blessing if an
effective means of preventing impacted canines
could be found.
Sadly un-erupted canines frequently escape
detection until a child is in their ‘teens’ when
encouraging spontaneous eruption can be difficult.
Early diagnosis can do much to reduce the risk of
impaction and Sambataro and his colleagues 14 drew
attention to the warning features. They studied the
incidence of canine impaction for 43 untreated
subjects at the age of 8½ and again at 14¼ with
frontal head films. Twelve subjects had developed
‘impacted’ canines. They found that the chance of
impaction was increased if the canine was nearer
the mid-sagittal plane and if the “posterior portion
of the hemi-maxilla was larger”. They suggest “the
Figure 2. The Stage 3 Orthotropic appliance
designed to train a child to keep their mouth
closed and improve their muscle tone.
use of techniques to widen the anterior part of the
maxilla without increasing the posterior part of
the upper jaw”, recommending a “fan” screw but
offered no clinical evidence to justify this approach.
However this suggestion is in line with the findings
of Schindel and Duffy 4 who found that “patients
with a transverse discrepancy are more likely to
have an impacted canine than those patients
without a transverse discrepancy”. While expansion
appliances are frequently used to provide
additional space for teeth in the maxilla there
seems to be little published evidence to suggest
that this effects the timing or incidence of canine
eruption whether impacted or not.
Most surgeons and some clinicians (15) take the
maxilla forward in severe malocclusions, but the
majority of orthodontists retract it. The possibility
that the maxilla would benefit from being moved
forward led to the development of a treatment
called Orthotropics® which involves expansion to
move the maxilla and incisors forward and provide
more space for the teeth.
It is not easy to establish the correct sagittal
position of the maxilla or of the upper incisors
but it is possible to estimate this by measuring
their relationship with the Cranial vault, using the
Frontal and Nasal bones as reference points 16 and
procline the incisors accordingly.
The maxilla is then expanded at a semi-rapid rate
(precisely one eighth of a millimetre per day) for
eight to ten millimetres, preferably before the age
of nine. In the short-term this moves the whole
maxilla forward and creates an anterior open bite
(Fig. 1) which may remain until the loss of the
buccal deciduous teeth but the procedure takes
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