As an orthodontist and health-care provider, I want to clearly
state that my first and foremost priority for my patients is
with my patients' welfare and to provide them the highest
quality of care and service while utilizing the most clinically
accepted and advanced technologies available. There have been
several different technologies that have made major impacts in
my private practice over the past 12 years. However, I consider
the integration of a cone beam computed tomography machine
(CBCT), more specifically the i-CAT, to have made one of the
biggest positive impacts in my practice.
Whenever a new technology is introduced to our profession,
there is a process that must take place prior to consideration of
the technology becoming a "standard of care." Four key stages
that make up this process: First, clinical research must substantiate
the efficacy and safety of the technology for our patients and
clinicians. Second, the technology must be taught properly to the
qualified providers who will be utilizing the technology to ensure
safety. Third, systems must be created to allow for effective
implementation of the technology in the clinical private practice
environment. And fourth, the costs associated with investment
of this technology must demonstrate a positive return on investment
both financially for the practice and clinically for the doctor
and the patient. CBCT is the middle of this process of
consideration for being the "standard of care" for our profession.
In this article, I would like to first discuss the risks and
benefits associated with CBCT. I would then like to review
the guidelines we have set up in our practice to minimize
the risk and maximize the incredible benefits. Finally, I
will share some clinical examples to demonstrate the benefits
As we all know, whenever we utilize any X-ray imaging for
our patients, there is an increased lifetime risk of cancer for
our patients. This is the one increased risk associated with
CBCT when compared to conventional 2D imaging.
However, the incredible benefits associated with CBCT have
been clearly substantiated with independent clinical research
over the past decade.1,2
The invention of CT was a Nobel-prize winning discovery and
today is still considered to be the greatest innovation in radiology
since the discovery of X-rays. The reason they were awarded with
one of the most prestigious honors in society is because CT is
considered to be one of the most important methods of radiological
diagnosis with far superior imaging in comparison to 2D
radiography with clearer, non-superimposed images and more
So how does a medical CT scanner work? I have attached
a diagram (Fig. 1) from the Food and Drug Administration
(FDA) to explain the mechanism with a medical CT scan.
There are two major differences between CBCT and medical
CT. First, CBCT uses a low-energy fixed-anode tube, similar
to that used in dental panoramic machines. Second and most
important, the mechanism capturing the data with CBCT is different
than the mechanism with medical CT. These differences
are illustrated in the diagram (Fig. 1). With the medical CT, the
head anatomy is exposed in small fan-shaped or flat slices as the
X-ray source and detector make multiple revolutions around the
patient's head while moving up or down the head anatomy.
While collecting this information with a medical CT, there is
overlapping of radiation.
With CBCT, the head anatomy is captured during the scan
with only one revolution around the head with a cone-shaped
beam. In contrast to the medical CT, the X-ray source and
detector of the CBCT rotate only one time around the head
anatomy and remain in the same vertical plane during the entire
scan. With CBCT, the X-ray source and detector never move up
or down during the single rotation.³
As a result, the same volumes of data with the head
anatomy can be captured with both CBCT and medical CT.
However, there is significantly decreased radiation exposure to
the patient with CBCT in comparison to medical CT, due to
the single cone-beam revolution around the patient's head. In
fact in the New York Times an article published the statistics of
CT medical scans versus those taken by an i-CAT. The article
stated a standard medical CT scan of the head exposes a
patient to approximately 2,000 microsieverts of radiation and
a standard i-CAT scan exposes a patient to approximately 74
microsieverts of radiation.
Radiation dosages to a patient from any CT scan are
dependent on two factors: 1) the type of CT scanner used and
2) the patient. Each CT scanner has its own unique settings
and mechanism. As a result, the radiation dosages for each CT
scanner will be different. The age and size of the patient and
tissue type to be scanned are also important factors that determine
the amount of radiation exposure to the patient. Young
patients are more sensitive to radiation than a mature adult.
Patients who are smaller in size are also more sensitive to radiation
than larger patients. Finally, tissues such as the lung,
breast and colon are much more sensitive to radiation than the
brain, skin and thyroid.4,5
Traditionally in orthodontics in the United States, prior to
initiating treatment for a patient, diagnostic records must be
taken. This typically requires obtaining photographs of the
patient, models of their bite and radiographs (typically a
panoramic X-ray and lateral cephalogram X-ray). However,
sometimes there might be other types of radiographs that will
be requested such as a posterior-anterior cephalometric X-ray,
submental vertex X-ray, occlusal X-ray and TMJ tomograms.
Some of the various types of radiographs utilized in orthodontics are listed with the amount of radiation exposure in
microsieverts in the graph (Fig. 3) from a study by Dr. John
Ludlow in September 2008, published in Journal of the
American Dental Association.
A standard set of radiographs in orthodontics consists of a 2D
digital panoramic X-ray (24.3 microsieverts) and a 2D digital lateral
cephalometric X-ray (5.6 microsieverts). The total radiation
exposure to the patient is approximately 30 microsieverts with
these two X-rays. With a "single i-CAT scan," all of this diagnostic
information can be captured at a very low radiation exposure
range of 30 to 160 microsieverts, which is the equivalent of or
only slightly higher radiation exposure to the patient with far
superior imaging and detail when compared to 2D radiographs.
The reason there is such a range for a single i-CAT scan is
due to three factors which determine the amount of radiation
exposure to the patient: 1) field of view (FOV), 2) resolution or
voxel size and 3) scan time.
FOV in radiology is defined as the maximum diameter of
the area of the scanned object from the detector that is represented
in the reconstructed image. With the i-CAT, the FOV
of the rectangular detector has a maximum scanned area of
23cm x 17cm. However, the FOV can be adjusted with i-
CAT's software application to be reduced to a FOV of 4cm x
16cm. In our practice, we typically use a FOV between 8cm x
16cm to 13cm x 16cm. We keep a CBCT log of every scan
taken. Our i-CAT logbook indicates that we typically use this
range for approximately 95 percent of our i-CAT scans. We
only use the maximum FOV of 23cm x 17cm less than five
percent of the time and this is only utilized for very large individuals.
As a result, the smaller the FOV, the less radiation
exposure there is to a patient.
A "voxel" can be defined as the smallest distinguishable box-shaped
part of a 3D image. Think of a voxel as a 3D pixel from
2D digital photography. With the i-CAT, the voxel setting can
be adjusted using the i-CAT's software application from a range
of 0.125 voxel to 0.4 voxel. The smaller the voxel, the higher the
resolution. As a result, 0.125 voxel offers the highest resolution
and 0.4 voxel offers the lowest resolution. As can be evidenced
by our i-CAT scanning protocol, approximately two-thirds of
our i-CAT scans are taken at 0.4 voxel or 0.3 voxel. We only utilize
the 0.2 voxel setting approximately one-third of the time for
SureSmile scans and for larger individuals. We never utilize the
highest resolution setting of 0.125 in our practice. As a result,
the lower the resolution, the less radiation exposure there is to
the patient. Conversely, the higher the resolution, the higher the
radiation exposure to the patient. Simply stated, there is a direct
correlation between the quality of the image and the amount of
radiation exposure to the patient.
"Scan time" is the setting for the amount of time it takes
for the X-ray source and detector to make a "single" 360-
degree rotation around the patient's head. The scan time setting
range varies from: 4.8 seconds to 26.9 seconds. We
typically utilize a scan time setting of 4.8 seconds, 8.9 seconds
and 14.7 seconds. In our orthodontic practices, rarely do we utilize the highest scan time setting of 26.9 seconds. This scan
time setting is really only utilized for very large individuals. As
a result, the shorter the scan time, the less radiation exposure
there is to the patient.
i-CAT Settings for Next Generation Machine (Dr. Lin)
Panorex only (ck 8s or eruption):
Diameter – 16cm, Height – 8cm, .4 voxel, 4.8 or 8.9 seconds.
Panorex/lateral ceph (all records):
Diameter – 16cm, Height – 13cm, .3 voxel, 4.8 or 8.9 seconds.
or for a larger FOV:
Diameter – 23cm, Height – 17, .3 voxel, 4.8 or 8.9 seconds.
For patients age 10 or under, use 4.8 seconds unless the
patient is a larger individual.
SureSmile scan that needs a panorex only:
Diameter – 16cm, Height – 8cm, .2 voxel, 14.7 seconds.
SureSmile scan that needs both panorex and lateral ceph X-rays:
Diameter – 16cm, Height – 13cm, .25 voxel, 14.7 seconds.
The bottom line is that we always try to keep the amount
of radiation exposure to our patients as low as possible, typically
in the range of 30 to 75 microsieverts. We do follow the
International Commission on Radiological Protection's
(ICRP) ALARA principle to keep radiation exposure "as low
as reasonably achievable." With our i-CAT, we now have a
technology in our orthodontic practice that allows us to significantly
reduce the radiation exposure to our patients in
comparison to a medical CT, and still allows us the incredible
benefits of 3D imaging so that we can make the best decisions
for treating our patients! I would also like to point out
that in our practice, we do not charge a fee for the i-CAT
scans for our patients. As a result, there is no financial incentive
for us to take extra scans of our patients. A scan is only
recommended if the doctor feels that it is clinically necessary
for the patient.
I will now illustrate how 3D CBCT imaging is superior to conventional
2D radiography leading to improved diagnosis and treatment
planning for our patients.6,7,8 For example, let us look at the
2D panoramic X-ray (Fig. 4a) that was created from a single,
low-radiation i-CAT CBCT scan.
With a single i-CAT scan, we can view 2D cross sections as
in the panorex above, but can also view things in 3D. Let us take
a look at the same patient in the 3D mode (Fig. 4b).
The red arrow above points to a supernumerary tooth positioned
behind the patient's permanent upper left central incisor.
Any orthodontist will understand the significance of not knowing
that an extra tooth is present under the bone and tissue can
put the patient at risk for damaging the roots of the adjacent
permanent teeth, especially if we begin moving teeth with
orthodontic appliances. The reason that you cannot see the extra
tooth in the 2D panoramic X-ray is because the extra tooth is
superimposed behind the root of the patient's upper left central
incisor. Because of the i-CAT, I was able to diagnose the extra
tooth, which has since been extracted, and the patient is currently
in orthodontic treatment with me without any risk to the
roots of the adjacent permanent teeth while in treatment. This
patient entered into my practice for a second opinion. The original
orthodontist never diagnosed the extra tooth because the
orthodontist did not see the extra tooth on the 2D panoramic
X-ray and lateral cephalometric X-ray, and a CBCT scan was
Another example of the incredible benefits of CBCT for our
patients is illustrated with figure 5. Let us first take a look at the 2D digital panoramic X-ray that was provided to us by the pediatric
dentist of our patient.
Compare this 2D digital panoramic X-ray (Fig. 5a) to a 3D
view that was created from an i-CAT scan of the same patient 12
months later (Fig. 5b).
The red arrow points to a "blue circular area" in the patient's
right lower jaw that is clearly abnormal and looks very suspicious
for pathology. In comparison, in the original 2D digital
panoramic X-ray taken before the start of treatment, the lesion
is not apparent and looks very similar in appearance to the same
area on the patient's left side as is illustrated by the red arrows
in Fig 5c.
As a result of the diagnosis of this lesion from the iCAT SureSmile
scan, the patient was given a referral to both an
oral surgeon and endodontist. The lesion was removed and
biopsied and was diagnosed as a traumatic bone cyst.
Unfortunately, the pathology had extended to the lower right
second premolar and root canal treatment was necessary for
that tooth as well. This is illustrated by the red arrow in the 2D
digital panoramic X-ray (Fig. 5d) that was provided to us by
the patient's pediatric dentist.
Now the question needs to be asked, What if this lesion
would have continued to go undiagnosed because it was not
evident in the 2D digital panoramic X-ray or other types of
2D dental X-rays. The answer to that question is that 1) the
lesion could have continued to grow larger over time, 2) the
lesion could have affected other teeth requiring additional
root canals or even the loss of teeth and 3) if the lesion continued
to grow and destroy the bone in the patient's lower jaw,
this would put the patient at greater risk for fracture of his
A 15-year-old male patient transferred into my practice for
a second opinion as the patient had been in orthodontic treatment
for approximately 14 months with the previous dentist. As
you can tell in the photographs and illustrated by the red arrows,
there is a significant problem with the eruption of this young
man's teeth in the right quadrant of his lower jaw (Fig. 6a). The
previous dentist had recommended extraction of his permanent
lower right first and second premolars because the dentist felt
that these two teeth were "ankylosed or stuck" under the bone
This young man had suffered trauma to the head and jaw
in an ATV accident as an 11-year-old. As a result, he had suffered
a fracture in his lower right jaw, which had required surgery
to repair the fracture with plates and screws. This is
illustrated by red arrows in the 2D panoramic X-ray (Fig. 6b)
that was created from a single, low-radiation iCAT scan. In
looking at a cross section of that same area in the 3D mode
(Fig. 6c), it is clearly evident with the red arrows that the
screws on the sides of the permanent lower right second premolar
are embedded into the roots of that tooth. This young
man also was suffering from chronic facial and jaw pain, frequent
headaches, difficulty in chewing, and his grades in
school had suffered since the accident.
As a result, I recommended removal of the plates and screws
with an oral surgeon and have since taken over his case. Final
photographs were taken on 4/21/2011, the day his braces were
removed (Fig. 6d). As is clearly evident, the teeth on his right
side have come together. More importantly, the patient no
longer suffers any side effects from his accident, his grades have
improved and he will be graduating from high school and going
to college in 2011.
Evaluation of the eruption patterns of the permanent teeth
is another example of the incredible benefits of CBCT.
Let's look at a patient who entered into my practice in
December of 2010. This patient's 2D panoramic X-ray (Fig. 7a)
was created from a single, low-radiation i-CAT scan.
Clearly evident and indicated by the red arrow in Fig. 7a,
this patient's permanent upper right canine is impacted underneath
the gum tissue and bone. However, is the permanent
canine in front of or behind the permanent upper right lateral
incisor? Also, are there any other areas of concern on this
The upper left red arrow in Fig. 7b clearly illustrates that the
permanent upper right canine is positioned behind the permanent
upper right lateral incisor and is impacted in the roof of the
mouth. The second red arrow illustrates that there is also a second
impaction that was not evident on the 2D panoramic X-ray
with the permanent upper left second premolar lying almost
horizontally in the roof of the mouth.
The surgeon will know exactly where to go to surgically
uncover these two teeth to allow me to bring them down into
their correct positions. This will minimize the amount of
trauma to the patient during the surgical procedure. I would
also like to point out that if a CBCT scan would have been
taken on this patient a couple of years earlier, perhaps both of
these impactions could have been avoided with an earlier diagnosis
and the recommendation of the extraction of the two primary
teeth. The negative consequences of impacted teeth are:
1) surgery and recovery time, 2) additional expense for the surgical
procedure, 3) additional time for orthodontic treatment
and 4) additional expense for orthodontic treatment due to
extra work involved.
One final example of the incredible benefits that CBCT has to
offer for our patients with diagnosis and treatment planning is
with a comparison of the images of the next two patients. The first
patient entered into my practice in September of 2009. When taking
a single, low-radiation i-CAT scan for our initial diagnostic
records, I discovered the root of his maxillary lateral incisor had
been destroyed, which is illustrated in the 2D panoramic X-ray
created from the i-CAT scan with the red arrow (Fig. 8).
The mother told me that they have always gone to see their
general dentist for their routine dental checkups every six
months. Unfortunately, the eruption path of the permanent
upper right canine had gone undiagnosed, and as a result, this
young man will eventually lose his permanent upper right lateral
incisor in the near future.
In comparison to this case above, the second patient's images
(Fig. 9) were created from a single, low-radiation i-CAT scan.
The area of concern again is illustrated by the red arrow.
However, on this 2D panoramic X-ray created from the i-CAT
scan, it does not appear as if the root of the permanent upper
right lateral incisor has been damaged or is in danger of being
damaged. We also cannot tell if the permanent upper right
canine is in front of or behind the permanent upper right lateral
incisor (Fig. 9b).
As can be evidenced by the red arrow, the eruption path of
the permanent upper right canine of this patient is coming
directly over the top of the root of the permanent upper right
lateral incisor and this patient has a significant risk of damage to
the root of the permanent upper right lateral incisor if treatment
were not rendered.
The reason I have brought these two patients' cases up for
comparison is because they are very similar cases. However, these two cases are also at two very different stages of dental
development, with the first patient being more mature and
approximately two years older.
With this image (Fig. 9b), I was able to diagnose a significant
risk for damage of the root of this patient's permanent upper
right lateral incisor due to the eruption path of the permanent
upper right canine that was not evident on the 2D panoramic X-ray.
As a result, I began treatment immediately and was able to
protect the root of this patient's permanent upper right lateral
incisor from any damage. In my personal professional opinion, if
a CBCT scan would have been taken on the first patient a couple
of years earlier, I believe the first patient's permanent upper
right lateral incisor could have been saved.
A Change in Application
Until 2007, CBCT has been viewed in orthodontics as a
diagnosis and treatment planning tool. However, in 2007, the
merging of the technologies of CBCT with a technology called
SureSmile gave the orthodontist the capability to utilize CBCT
not only as a diagnosis and treatment planning tool but also
gave us the capabilities for CBCT to become "actively" involved
in the treatment of our patients!
SureSmile is a technology first introduced to the orthodontic
profession approximately seven years ago. SureSmile's technology
incorporates computer hardware, a scanner (intra-oral
scanner or CBCT scanner) and their proprietary 3D
CAD/CAM software applications in combination with fixed
orthodontic appliances or braces. The way SureSmile works is
after we bond the brackets on a patient, we then need to scan
the patient's teeth and brackets. Using SureSmile's proprietary
software, the orthodontist is able to reset the patient's incorrect
bite to an ideal bite and then will bend a customized SureSmile
wire with memory that will move all the teeth into the correct
positions at once. As a result, SureSmile allows us to correct our
patient's alignment and bite issues with a high degree of precision
and also allows us to reduce treatment time by an average
of 40 percent.9,10 My average treatment time prior to SureSmile
for all of my full orthodontic and Phase II cases used to be 24
months. My average treatment time with SureSmile for these
same cases is now 14 months.
When SureSmile was first introduced, the only option at
that time was to utilize an intra-oral scanner to scan the
patient. As a result, SureSmile's technology was limited to only
capturing the clinical crowns of the teeth in combination with
the brackets as illustrated in figure 10. We are not able to see
the roots of the teeth because we cannot scan them with the
As orthodontists, our specialty is responsible for creating
beautiful smiles and correcting bite problems for our patients.
However, in the process of moving teeth, we are also moving the
roots of the teeth as well. Until recently, there was no technology
available to orthodontists that would allow us to be able to
accurately evaluate root positions prior to the start of treatment
or determine if we were moving the roots of our patient's teeth
into the most ideal positions at the completion of their orthodontic
That is until 2007, when SureSmile gave orthodontists the
capability to CBCT scan our patients so that we could evaluate
and correct not only the positions of the crowns of their teeth
but also the roots of their teeth to a very high degree of precision
and accuracy. Several studies have shown that evaluation of
root positions utilizing a 2D panoramic radiograph is an inaccurate
Let us look at what the benefits are with understanding what
is happening with both crown and root movement of the teeth
while a patient is in orthodontic treatment. With the SureSmile
setup of the patient in figure 11 without the roots present, it
appears as if this patient has a very nice fitting bite on the
patient's right side.
However, let us look at this same patient a bit more closely
when displaying the roots of the patient's teeth with all of the
teeth in the exact same positions. It is clearly evident in the second
image (Fig. 12), as is indicated by the red arrow, that the
roots of the permanent upper right first and second premolars
are colliding. The concern here is that with the collision of the
two roots, this can 1) prevent tooth movement that might go
undiagnosed or 2) in the worst case scenario, it might cause
damage to the roots of the teeth themselves.
By truly understanding the anatomy of the roots of the
teeth, with SureSmile's software applications, this allows the orthodontist to better position both the crowns and the roots of
the teeth into the most ideal positions. This is illustrated in
Figure 13a with the red arrow. There is now clearly space
between the roots of these two teeth. I have also included before
and after photos of the patient's completed case (Figs. 13b-c),
which I completed in only 12 months with SureSmile. Without
SureSmile, I estimate that it would have taken me approximately
18 months to complete her case.
Another example of the importance of understanding
both the crown and root positions for orthodontic treatment
with the following patient's images (Figs. 14a-b). As indicated
by the red arrows, this patient's permanent lower left second
premolar is partially impacted on the day of her SureSmile
scan. Obviously there is significant movement of both the
crown and the root of the tooth that needs to take place.
With SureSmile's software applications, I am able to reposition
both the crowns and the roots of the teeth into the most
ideal positions. This is illustrated in this patient's SureSmile
setup (Figs. 15a-c) with her before and after photos of the
Her total treatment time took only 14 months from start to
finish with SureSmile, even with the impacted tooth. If I would
have treated her case without SureSmile, I would estimate that
it would have taken me approximately 20-24 months to complete
With ideal positioning of the crowns of the teeth in combination
with the ideal positioning of the roots of the teeth in
the bone, this leads to increased stability with the bite and a decreased potential for orthodontic relapse in the future.
This also leads to greater periodontal stability for the long-term,
resulting in a decreased potential for gum recession
and bone loss as we age.12 I personally feel that it is phenomenal
that we now have these capabilities for the orthodontist
to be able to predictably determine both crown and root
movement because of the integration of the technologies of
CBCT and SureSmile.
In conclusion, I would like to review one final case to illustrate
the tremendous benefits which CBCT has to offer both
to us, the clinicians, and our patients.
This young lady presented to me for a new patient examination
in July of 2011 (Fig. 16). She was 13 years and 11
months. Her father is a general dentist and has been monitoring
her dental needs on an annual basis. She has a Class I malocclusion
with mild spacing present in both maxillary and
mandibular arches. An i-CAT scan was recommended by me
after my initial clinical evaluation. Upon further evaluation of
her lateral cephalogram (Fig. 17a) and panorex (Fig. 17b), it
appears that this is a very straightforward orthodontic case and
could be considered a "routine" orthodontic case by some.
However, after sending her i-CAT scan to an oral radiologist,
it was discovered that a radiopacity was present in her right maxillary sinus with distortion and bowing present of the
posteriolateral wall of her right maxillary sinus as is evidenced by
the red arrow in the axial cross section (Fig. 18).
As a result, an ENT referral was immediately given to the
family for further evaluation and treatment. The reason that I
would like to conclude with this case is because this case truly
demonstrates the importance of CBCT in diagnosis and treatment
planning, especially as our profession of orthodontics continues
to advance with the technological changes that are
making us better clinicians and allowing us to provide a higher
quality of care. The question needs to be asked, What if an i-
CAT scan had never been taken on this patient and her pathology
had gone undiagnosed for several years because the
pathology was not evident in the 2D radiographs? Without a
doubt, I think we all know that this young lady would have a
much greater risk with health issues directly related to this.
In my practice, I never consider any case to be a "routine"
orthodontic case until that case has been completed and I have
had an opportunity to re-evaluate. I treat each and every case
that comes through my practice with "universal precaution"
while completing my diagnosis and treatment planning.
Radiographic imaging is only recommended when I see the need
for it. As clinicians, we must understand that there are risks that
we are exposing our patients to when we are making these recommendations
and we must minimize these risks by controlling
the amount of radiation exposure to the patient and making certain
that the benefits will outweigh the risks. With CBCT, we
now have the capabilities to do so.
In summary, I personally believe that our esteemed profession
of dentistry should be given significant credit and recognition for the development of the technology of
CBCT to provide our patients with a low-radiation
3D imaging alternative to medical CT.
However, CBCT still affords us all the benefits of
medical CT with 3D imaging. This has led to an
improved quality of care with diagnosis and treatment
planning for our patients. With the integration
of the technologies of CBCT and SureSmile,
CBCT now has an additional benefit as it is being
utilized with the active therapeutic care of our
patients. Diagnosis and treatment planning with
actual treatment of our patients are all transitioning
from the 2D into the 3D world. It is my belief
that CBCT will be considered the standard of care
in orthodontics in the very near future, especially
since the technology has now advanced to bring
the radiation exposure levels to our patients down
to levels that are very comparable to a digital
panorex and lateral cephalogram.
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