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INTRODUCTION
CBCT IN ORTHODONTICS
To understand the difference between CT imaging and other
techniques, x-ray of the head should be considered. Using basic x-ray
techniques, the bone structures of the skull can be viewed. With
magnetic resonance imaging (MRI), blood vessels and soft tissue can be
viewed, but clear, detailed images of bony structures cannot be obtained.
On the other hand, x-ray angiography can provide a look at the blood
vessels of the head, but not soft tissue. CT imaging of the head can
provide clear images not only of soft tissue, but also of bones and blood
vessels.
CT imaging is commonly used for diagnostic purposes. In
fact, it is a chief imaging method used in diagnosing a variety of cancers,
including those affecting the lungs, pancreas, and liver. Using CT
imaging, not only can physicians confirm that tumors exist, but they can
also pinpoint their locations, accurately measure the size of tumors, and
determine whether or not they've spread to neighbouring tissues.In
addition to the diagnosis of certain cancers, CT imaging is used for
planning and administering radiation cancer treatments, as well as for
planning certain types of surgeries. It is useful for guiding biopsies and a
range of other procedures categorized as minimally invasive. Thanks to
its ability to provide clear images of bone, muscle, and blood vessels, CT
imaging is a valuable tool for the diagnosis and treatment of
musculoskeletal disorders and injuries. It is often used to measure bone
mineral density and to detect injuries to internal organs. CT imaging is
even used for the diagnosis and treatment of certain vascular diseases
that, undetected and untreated, have the potential to cause renal failure,
stroke, or death.
In layman's terms, CBCT is a compact, faster and safer version
of the regular CT. Through the use of a cone shaped X-Ray beam, the size
of the scanner, radiation dosage and time needed for scanning are all
dramatically reduced.
A typical CBCT scanner can fit easily into any dental ( or
otherwise ) practice and is easily accessible by patients. The time needed
for a full scan is typically under one minute and the radiation dosage is up
to a hundred times less than that of a regular CT scanner.
There has been an escalating interest in three dimensional
imaging devices over the last decade. orthodontics are beginning to
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appreciate the advantages that the third dimension gives to clinical
diagnosis, treatment planning and patient education with cbct
technology all possible radiographs can be taken in under 1 minute. The
orthodontics now has the diagnostics quality of periapicals,
panormic,cephalograms and occlusal radiographs and tmj series at their
disposal along with views that cannot be produced by regular
radiographic machines like axial views and separate cephalograms for
the right and left sides.
Prior to seeing the patient, the tri-planner view of the CBCT is
screened for any observable pathology. This is something we were only
able to do in a limited manner with two dimensional .The second task is
to review the tri-planner view examining the airways. This includes the
retro-glossal airway, retropalatal airway, nasal passageways and all
sinuses. Adequacy of airways can affect skeletal growth patterns in
growing individuals and can also affect dental stability in growing as
well as non growing individuals. The airways are also a reflection of
skeletal relationships and can give us a clue of those individuals that may
have or be at risk for sleep disorders including obstructive sleep apnea.
In addition, we will sometimes find sinus polyps, maxillary sinus
infections and even ethmoid sinus disease. Upon finding pathology, the
appropriate referrals are made accompanied by a video copy of the
CBCT on a CD radiographs looking through a great depth of anatomy
with inherent distortion due to the manner in which the image was
obtained within the alveolar trough, relative horizontal bone levels and
root proximity. Recognizing asymmetries and developing asymmetries
is an extremely important part of the orthodontic diagnostic process as
this has profound affects upon how we plan for the individual's
treatment. Following the tri-planner investigations, I will then build the
TMJ studies examining form, volume and position of the condyles
within the fossa as well as the anatomy of the fossa itself. Because our
patients have either completed their health history questionnaires on-
line or in our office prior to my review of all of the above I am able to add
this information to the diagnostic information provided by the CBCT
and the information obtained by my treatment coordinator all before I
have even met my patient. To have this information at my initial exam
only enhances the diagnosis, treatment planning, an deducational
process. Prior to my viewing the CBCT volume in the proprietary
software another staff member takes a "step backwards in time" and
6
UTILIZATION OF CBCT IN AN ORTHODONTIC PRACTICE
Ashish Aggarwal Nupur Agarwal Sowmya G. V. Md.Asad Iqubal
† †† ††† †††† †††††
Nitin Upadhyay
† Senior Lecturer Department of , Institute of Dental Sciences, Bareilly
†† Senior Lecturer Department of , Institute of Dental Sciences, Bareilly
††† Senior Lecturer Department of , Institute of Dental Sciences, Bareilly
Senior Lecturer Department of , Institute of Dental Sciences, Bareilly
Department of , Institute of Dental Sciences, Bareilly
Date of Receiving : 21/Mar/2013
Date of Acceptance : 08/Apr/2013
Oral Medicine and Radiology
Oral Medicine and Radiology
Oral Medicine and Radiology
Oral Medicine and Radiology
Oral Medicine and Radiology
††††
††††† P. G. Stutent
, , , ,
, (U.P).
, (U.P).
, (U.P).
, (U.P).
, (U.P).
Abstract:
Key words :
CBCT is a compact, faster and safer version of the regular CT, through the use of a cone shaped x-ray
beam. The size of the scanner, radiation dosage and time needed for scanning are all dramatically reduced and
can be easily fitted into the dental chair.It involves the use of rotating x-ray equipment, combined with a digital
computer, to obtain images of the body. Using CT imaging, cross sectional images of body organs and tissues
can be produced. CT imaging can provide views of soft tissue, bone, muscle, and blood vessels. Computed
tomography (CT) imaging, is also referred as computed axial tomography (CAT) scan clarity.
Cone Beam, Radiology, Medicine, Implantology, Orthodontic.
Cone Beam Computed Tomography
05
Journal of Dental Sciences & Oral Rehabilitation 2013; July - September
builds 2Dlateral and posterior-anterior cephalograms in Dolphin 3D
(orthodontic imaging software) to allow me to digitize the cephalograms
and provide me with further diagnostic and treatment planning
information. This process is at this time a necessity for the orthodontist
but 3D digitizing will soon be here and infact is being developed and
tested at this time. The quality of the cephalograms built from the CBCT
is without a doubt a huge improvement over the conventional
2Dradiographs. The CBCT and extra-oral photographs are taken with an
operator assisted first tooth contact centric relation wax bite registration.
We can make more appropriate treatment decisions as opposed to images
taken in habitual jaw positions that may not reflect the true relationship
of the mandible to the maxilla and thus may inaccurately reflect condylar
position and the relative dental relationships The superior diagnostic
information provided by CBCT over conventional radiographic
technology dictates that we make the transition from 2D diagnosis and
treatment planning to 3D sooner rather than later. Most all of us have
inherent asymmetries and skeletal discrepancies but the greater the
magnitude of these discrepancies the more important 3Dimaging,
digitization and treatment planning becomes. For example, treatment
planning of orthognathic surgical cases in 3D will provide us a more
complete picture of treatment options and projected treatment outcomes,
which in the end is a huge benefit for the patient.
In the field of periodontology and implantology, assessment of
the condition of teeth and surrounding alveolar bone depends largely on
two-dimensional imaging modalities such as conventional and digital
radiography though these modalities are very useful and have less
radiation exposure, they still cannot determine a three dimensional
architecture of osseous defects. Hence an imaging modality which
would gives an undistorted vision of a tooth and surrounding structures
is essential to improve the diagnostics potential. CBCT provides 3D
images that facilitate the transition of dental imaging from initial
diagnosis to image guidance throughout the treatment phase. This
technology offers increased precision, lower doses and lower costs when
compared with medial fan-beam CT.
In the field of periodontology, assessment of the condition of
teeth and surrounding alveolar bone depends largely on traditional two-
dimensional imaging modalities such as conventional radiography and
digital radiography. Though these modalities are very useful and have
less radiation exposure, they still cannot determine a three-dimensional
(3D) architecture of osseous defects. Hence, an imaging modality which
would give an undistorted 3D vision of a tooth and surrounding
structures is essential to improve the diagnostic potential. A well
diagnosed periodontal lesion warrants an appropriate treatment.
In the medical field, the 3D imaging using computed tomography (CT)
has been available now for many years, but in the dental specialty, its
application is restricted to the use in cases of maxillofacial trauma and
diagnosis of head and neck diseases. Routine use of CT in dentistry is not
accepted due to its cost, excessive radiation, and general practicality. In
recent years, a new technology of cone-beam CT (CBCT) for acquiring
3D images of oral structures is now available to the dental clinics and
hospitals. It is cheaper than CT, less bulky and generates low dosages of
X-radiations. The innovative CBCT machine (fig 1] designed for head
and neck imaging are comparable in size with an orthopantomograph.
CBCT provides rapid volumetric image acquisition taken at
different points in time that are similar in geometry and contrast, making
it possible to evaluate differences occurring in the fourth dimension
time. In its various dental applications, images of jaws and teeth can be
visualized accurately with excellent resolution can be restructured three
dimensionally, and can be viewed from any angle (Fig 2). Most
significantly, patient radiation dose is five times lower than normal CT.
Today, CBCT scanning has become a valuable imaging
modality in periodontology as well as implantology. For the detection of
smallest osseous defects, CBCT can display the image in all its three
dimensions by removing the disturbing anatomical structures and
making it possible to evaluate each root and surrounding bone. In
USES OF CBCT IN IMPLANTOLOGY
7
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implant treatment, appropriate site or size can be chosen before
placement, and osseointegration can be studied over a period of time.
This review discusses all the finer details of CBCT which has
added a third dimension to the imaging in periodontics.
CBCT is being increasingly used for point of service head &
neck and dento-maxillofacial imaging. This technique provides
relatively high isotrophic spatial resolution of osseous structures with a
reduced radiation dose compared with conventional CT scans. In this
second installement in a 2-part review, the clinical application in the
dentomaxillofacial and head & neck regions will be explored, with
particular emphasis on diagnostics imaging of the sinuses, temporal
bone and craniofacial structures.
Today's computer aided design & manufacture (CAD/CAM)
technologies contribute greatly to restorative dentistry & provide
cl ini cal s wi th advanced t reatment opti ons for vari ous
indications,including inlays,onlays,fixed dentures & full dentures,thin
veneers and crowns.These systems also allow use of many restorative
materials,including metal,metal-ceramic,compositive & all ceramic, to
best meet the needs of the care & patients. Further CAD/CAM systems
are available for both chairable & laboratory applications,so dentists
now have the ability to create highly aesthetic & strong restoration in
office.
USES OF CBCT IN HEAD & NECK REGION
USES OF CBCT IN PROSTHODONTICS
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Cone beam CT (CBCT) is an advancement in CT imaging that
has begun to emerge as a potentially low-dose cross-sectional technique
for visualizing bony structures in the head and neck. The physical
principles, image quality parameters, and technical limitations relevant
to CBCT imaging were discussed in Part 1 of this 2-part series. The
second part presented here will highlight the evidence related to CBCT
applications in head and neck as well as dentomaxillofacial imaging.
Controversial aspects of this technology will also be addressed,
including limitations in image quality and its often office-based
operational model.
CBCT was first adapted for potential clinical use in 1982 at the
Mayo Clinic Bio dynamics Research Laboratory. Initial interest focused
primarily on applications in angiography in which soft-tissue resolution
could be sacrificed in favour of high temporal and spatial-resolving
capabilities. Since that time, several CBCT systems for use have been
developed both in the interventional suite and for general applications in
CT angiography. Exploration of CBCT technologies for use in radiation
therapy guidance began in 1992, followed by integration of the first
CBCT imaging system into the gantry of a linear accelerator in 1999.
The first CBCT system became commercially available for
dentomaxillofacial imaging in 2001 (New Tom QR DVT 9000;
Quantitative Radiology, Verona, Italy). Comparatively low dosing
requirements and a relatively compact design have also led to intense
interest in surgical planning and intra operative CBCT applications,
particularly in the head and neck but also in spinal, thoracic, abdominal,
and orthopedic procedures. Diagnostic applications in CT
mammography and head and neck imaging are also under evaluation.
The technical and clinical considerations pertaining to CBCT imaging in
many of these applications have been the subjects of several recent
reviews.The recent review by Dörfler et al of the neurointerventional
applications of CBCT is of particular interest to the field of
neuroradiology.
5
ADVANTAGES OF CBCT
Being considerably smaller, CBCT equipment has a greatly
reduced physical footprint and is approximately 20-25% of the cost of
conventional CT. CBCT provides images of high contrasting structures
and is therefore particularly well- suited towards the imaging of osseous
structures of the craniofacial area. The use of CBCT technology in
clinical dental practice provides a number of advantages form
axillofacial imaging. These include
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Journal of Dental Sciences & Oral Rehabilitation 2013; July - September
RAPID SCAN TIME
BEAM
IMAGE ACCURACY
REDUCED PATIENT RADIATION DOSE COMPARED TO
CONVENTIONAL CT.
Because CBCT acquires all projection images in a single
rotation, scan time is comparable to panoramic radiography. This is
desirable because artefact due to subject movement is reduced.
Computer time for dataset reconstruction however is substantially
longer and varies depending on FOV, the number of basis images
acquired, resolution and reconstruction algorithm and may range from
approximately 1 to 20 minutes.
Collimation of the CBCT primary x-ray beam enables
limitation of the x-radiation to the area of interest. Therefore an optimum
FOV can be selected for each patient based on suspected disease
presentation and region of interest. While not available on all CBCT
systems, this functionality is highly desirable as it provides dose savings
by limiting the irradiated field to fit the FOV.
CBCT imaging produces images with sub-millimeter
isotropic voxel resolution ranging from0.4 mm to as low as 0.09 mm.
Because of this characteristic, subsequent secondary(axial, coronal and
sagittal) and MPR images achieve a level of spatial resolution that is
accurate enough for measurement in maxillofacial applications where
precision in all dimensions is important such as implant site assessment
and orthodontic analysis
The effective dose varies for various full field of view
CBCT devices from 29-477 Sv depending on the type and model of
CBCT equipment and FOV selected (Table 2) (Schulze et al.,2004; Mah
et al., 2003; Ludlow et al.,2003, 2006, 2007). Patient positioning
modifications (tilting the chin) and use of additional personal protection
(thyroid collar) can substantially reduce dose by upto 40% (Ludlow et
al., 2006). These doses can be compared more meaningfully to dose from
a single digital panoramic exposure(Ludlow et al., 2003), equivalent CT
dose (Ngan et al., 2002), or the average natural background radiation
exposure for Australia (1,500 Sv) (ARPANSA, 2007)in terms of
background equivalent radiation time (BERT) (MacDonald,
1997).CBCT provides an equivalent patient radiation dose of 5 to 80
times that of a single film-based panoramic radiograph, 1.3% to 22.7%
of a comparable conventional CT exposure or 7 to 116 days of
background radiation.
(E)
μ
μ
s of
A number of novel medical diagnostic imaging modalities
have emerged recently. Cone beam computed tomography (CBCT) is a
radiographic imaging method that allows accurate, three-dimensional
imaging of hard tissues. CBCT has been used for dental and
maxillofacial imaging for more than ten years now and its availability
and use are increasing continuously. However, at present, only “best
practice” guidelines are available for its use, and the need for evidence-
based guidelines on the use of CBCT in dentistry is widely recognized.
CBCT is more reliable in evaluating the number of mandibular third
molar roots than panoramic radiography. CBCT scanners provide
adequate image quality for dentomaxillofacial examinations while
delivering considerably smaller effective doses.
Even with CT imaging, clinicians have laboured to link the
information from the scan data to the surgical site, transferring angles
and positions manually. This is overcome with interactive software
applications that provide this information seamlessly.
As CBCT has become the state-of-the-art, the race is on to
identify opportunities which benefit from the digital information
embedded in each scan. Guided implant surgery has evolved as an
important modality and aid in transferring the virtual 3-D plan to the
ORAL RADIOLOGY
CONCLUSION
16
patient. Surgical templates can then be laboratory fabricated on stone
casts, or directly CT-derived via stereo lithography, taking the scan data
and turning it into solid resin models of the patient's mandible or maxilla.
However, as more companies invest in 3-D digital dentistry solutions,
linking the technologies together has become a reality. This presentation
will demonstrate how digital dentistry is evolving into a mainstream
dentistry, allowing everyone to achieve successful "restoratively-
driven" implant dentistry.
1. Kau CH, Richmond S. Current products and practice three
dimensional cone beam computerized tomography in orthodontics.
J Ortho 2005;32:282-93.
2. Mohan R, Singh A, Gundappa M. Three-dimensional imaging in
periodontal diagnosis Utilization of cone beam computed
tomgraphy. J Indian Soc Periodontol. 2011;15(1):7-11.
3. Miracle AC, Mukherji SK. Conebeam CT of the head and neck,
part 2: clinical applications. AJNR Am J Neuroradio
2009;30(7):1285-92.
4. Alamri HM, Sadrameli M, Alshalhoob MA, Sadrameli M, Alshehri
MA. Applications of CBCT in dental practice: a review of the
literature. Gen Dent. 2012; 60(5):390-400.
5. Danforth RA, Peck J, Hall P. Cone beam volume tomography: an
imaging option for diagnosis of complex mandibular third
molar anatomical relationships. J Calif Dent Assoc
2003;31(11):847-52.
6. Halazonetis DJ. From 2-dimensional cephalograms to 3-
dimensional computed tomography scans. Am J Orthod
Dentofacial Orthop 2005;127(5):627-37.
7. Mah J, Hate er D. Current status and future needs in craniofacial
imaging. Orthod Craniofac Res. 2003; 6(1):79-82.
8. Noar JH, Pabari S. Cone beam computed tomography current
understanding and evidence for its orthodontic applications? J
Orthod 2013;40(1):5-13.
9. Chaushu S, Chaushu G, Becker A. The role of digital volume
tomography in the imaging of impacted teeth. World J Orthod
2004;5(2):120-32.
10. Ericson S, Kurol PJ. Resorption of incisors after ectopic eruption
of maxillary canines: a CT study. Angle Orthod. 2000;70(6):415-
23.
11. Mah J, Enciso R, Jorgensen M. Management of impacted
cuspids using 3-D volumetric imaging. J Calif Dent Assoc.
2003;31(11):835-41.
REFERENCES
12. Aboudara CA, Hatcher D, Nielsen IL, Miller A. A three-
dimensional evaluation of the upper airway in adolescents.
Orthod Craniofac Res. 2003;6:173-5.
13. Robb RA. The Dynamic Spatial Reconstructor: An X-Ray Video-
Fluoroscopic CT Scanner for Dynamic Volume Imaging of Moving
Organs. IEEE Trans Med Imaging. 1982;1(1):22-33.
14. Fahrig R, Nikolov H,Fox AJ, Holdsworth DW. A three-
dimensional cerebrovascular flow phantom. Med Phys.
1999;26(8):1589-99.
15. Covalcanti MG. Cone beam computed tomegraplic imaging
perspective, challenges and the impact of near trend future
applications. J Craniofac Surg 2012;23(1):279-82
16. Suomalainen II., Kiljunen T, Kaser Y, Peltola J, Kortesniemi M.
Dosimetry and image quality of four dental cone beam computed
tomography scanners compared with rnultislice computed
tomography scanners, Dentomaxillofac Radiol. 2009;38(6):367-
78.
Corresponding Address:
Email:
Dr. C. Ram Mohan
[email protected]
Corresponding Address:
Email:
Dr. Ashish Aggarwal
[email protected] mail.com
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Journal of Dental Sciences & Oral Rehabilitation 2013; July - September
LIST OF PHOTOGRAPHS
Fig 1 CBCT Machine
Fig 2 CBCT Image
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Journal of Dental Sciences & Oral Rehabilitation 2013; July - September

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