Orthotown November 2017 - 46

Table 1

STAGE

3-D IMAGING*

2-D IMAGING**

Initial records

15 microsieverts (FFOV)

15-30 microsieverts

Bracket reposition/progress records

10 microsieverts (LFOV dental only)

15-30 microsieverts

Final records

15 microsieverts (FFOV)

15-30 microsieverts

Total:

40 microsieverts

45-90 microsieverts

* 3-D CBCT dose based on ULD setting on Planmeca ProMax Mid.
** lateral cephalometric and panoramic radiograph for each. 2-D radiographs dose based on study in Footnote 3.

"Because of the
additional information
and lower radiation
associated with ULD
3-D radiography, we
consider it safe to
recommend its routine
use for all orthodontic
patients. ... In fact, we
believe that soon the
use of 2-D radiography
will come under fire
because of the higher
radiation doses patients
receive from its use."

Figs. 12 and 13: Limited alveolar boundary in 1-millimeter sagittal slice (left) and axial slice (right). The white line shows
the outline of the root; the red lines show the outline of the alveolar ridge.

revealing exactly how much bone would be
present if that treatment plan were carried
through. We must also consider now the
possibility that in many cases there is a lack of
bone in the direction we would like to move the
teeth, and whether treatment is still indicated.
Alveolar boundary conditions (Figs. 12 and
13) are becoming an important consideration,
given our new access to this information.
Before the use of CBCT, it was impossible to
evaluate boundary conditions radiographically.
We do not plan any case without evaluating
whether bone is available in the region where
tooth movement is to occur, and specifically
available in the direction that the movement
is to take place.

Radiation concerns
One of the biggest areas of concern about
CBCT technology has been the amount of
radiation patients are exposed to-particularly
in orthodontics, where most patients are children
who are more susceptible to ionizing radiation.
Research published in 2008 reported that
during a 2-D radiograph, the average radiation
exposure is 14-24 microsieverts. The exposure

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during a lateral cephalometric head film and
a PA cephalometric head fi lm was about 5
microsieverts each.3
Typical radiographic imaging in most
offices vs. our imaging protocol are compared
in Table 1, which includes imaging during the
three points in treatment we generally take
radiographs: initial records, progress records
and final records. With ULD CBCT, radiation
levels can be reduced by as much as one-half
from what's associated with traditional 2-D
radiography.
When thinking about radiation exposure,
diagnostic quality must stay at the forefront
of the discussion. Some dentists are refining
the ALARA principle ("as low as reasonably
achievable") and instead referring to ALADA
("as low as diagnostically acceptable"). Their
point is that just because a lower radiation dose
may be achievable, it doesn't necessarily mean
that it's diagnostically acceptable. Depending
upon the indication of the scan, clinicians must
use the appropriate field of view, mA and KVP
settings, as well as resolution, to obtain what
would be a diagnostically acceptable image.4
In our offices, initial and final records

Figs: 12 and 13 Courtesy of Planmeca Romexis.

Comparing radiation doses of 2-D and 3-D imaging for a typical child patient

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Table of Contents for the Digital Edition of Orthotown November 2017