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Douglas L. Chenin, DDS
Dr. Douglas L. Chenin earned his DDS de-gree from the University
of the Pacific Ar-thur A. Dugoni School of Dentistry in
SanFrancisco. He is the Director of Clinical Af-fairs at Anatomage
Inc, the creators of theInVivoDental 3D Imaging Software andthe
AnatoModel Service for advanced ap-plications with cone beam
computed to-mography (CBCT) imaging. He is involvedin the research
and development of thecompany’s 3-dimensional technology
andapplications. Dr. Chenin is involved in facil-itating and
participating in research pro-jects throughout multiple dental
schoolsacross the nation. He is also Adjunct Facultyat the
University of the Pacific Arthur A.Dugoni School of Dentistry in
the Ortho-dontics Department, and an Adjunct Pro-fessor at the
University of Nevada LasVegas School of Dental Medicine in
theClinical Science Department, where heteaches both residents and
faculty how touse 3-dimensional imaging to its fullest po-tential
for both clinical and research appli-cations.
Douglas L. Chenin
SCIENTIFIC ARTICLE
3D Cephalometrics: The NewNormDouglas L. Chenin, DDS
With the advent of cone beam computed tomography (CBCT),
thediagnostic foundations of dentistry have been forever changedand
advanced into a new era of 3-dimensional (3D) possibilities.
In the case of implant planning, which was among the first
applications of thistechnology, the exact 3D location of the
implant could be preplanned andeven guided during surgery. This was
a major advancement in implant plan-ning above and beyond
traditional radiographic images, such as panoramic,bitewing, and
periapical films, all of which are subject to magnification
errorsand dimensional distortion. However, with CBCT imaging, the
images arecaptured in their true anatomic size and shape, and
therefore offer themost accurate treatment planning potential.1–3
For these reasons, CBCTimaging was quickly harnessed for multiple
imaging applications invarious fields of dentistry, from
diagnostics to surgical planning, and fromorthodontics to
endodontics; it has permeated all fields of our profession.The
scope of this article will highlight the salient features of how
CBCTimaging is being used for orthodontic and dentofacial
orthopedicapplications.
HISTORICAL 3-DIMENSIONAL
PERSPECTIVE
In April of 1931, Dr. B. HollyBroadbent, one of the founding
fa-thers of orthodontics, publishedone of the most important
papersin orthodontics, titled ‘‘A new X-ray technique and its
application toorthodontia’’ in the Angle Orthodon-tist journal.4 It
was in this publica-tion that Dr. Broadbent advocatedthe importance
of analyzing thedental and craniofacial structures si-multaneously
in both the frontaland lateral cephalometric projec-tions to
achieve the most accurate3D perspective.4 Furthermore, heexplained
his system to achievethis with the most accurate resultsusing a
device he developed calledthe Broadbent head holder. This de-vice
allowed for both the frontal andlateral cephalometric images to
be
captured with the least amount ofdistortion and magnification,
sothat both images could be correlatedside by side and analyzed
together(Figure 1). Approximately 70 yearslater, the CBCT machine
was re-leased and actually does somethingquite in line with Dr.
Broadbent’sideas. Rather than just correlatingtwo images—a frontal
and lateralcephalometric radiograph—CBCTmachines take hundreds of
projec-tion x-rays as the x-ray source ro-tates in incremental
angles aroundthe patient’s head and fuses themall together with
perfect accuracy,without size distortion or misalign-ment. This
creates a full 3D and vol-umetric radiograph that can beanalyzed
from any perspective. Fur-thermore, the CBCT image clearlydefines
both the hard and soft
-
Figure 1. Frontal and lateral cephalometric images together side
by side achieve themost accurate 3-dimensional perspective of the
time. This system was developed byDr. Broadbent and published in
1931.
3D CEPHALOMETRICS: THE NEW NORM
tissues with a wide range of gray-scale values based on anatomic
den-sity. In so doing, the CBCT machineprovides the most complete
and ac-
Figure 2. A cone beam computed to-mography scan of a patient
showingthe full three dimensional volume ren-dering of the image.
The differenttissues, such as hard tissues and soft tis-sues, are
automatically colorizeddepending on their anatomic density.Image
taken with the iCAT CBCTmachine (Imaging Sciences Interna-tional)
and visualized in the Invivo5 3Dimaging software (Anatomage).
52
curate picture of the hard and softtissues of a patient’s
craniofacialmorphology (Figure 2). The accu-rate 3D nature of CBCT
images ren-ders the technology powerful withuntapped potential.
CBCT ma-chines effectively create a virtual pa-tient that can be
used for any type ofmeasurement or visualization.
DYNAMIC CONE BEAM
COMPUTED TOMOGRAPHY
STUDY MODELS
The CBCT scan of the patient pro-vides a complete 3D volume of
datathat can be viewed from any per-spective, rotated to any
degree, andsliced in any manner. It can be slicedalong the arch to
create a series ofslices along the arch or it can be re-constructed
into traditional orienta-tions like panoramic images(Figure 3).
These data can also bemeasured from any perspectiveand plane, with
linear, angular, cir-cumferential, area, and volume
mea-surements.1–3 Individual structureslike teeth and specific
bones, suchas the maxilla and mandible, canbe segmented out and
modeled in3D. Volumetric or 3D modeling isa method of defining the
specificboundary of a structure, isolatingit, and then coloring the
surface
Alpha
(also called an isosurface), with anopaque colorization for
optimalvisualization (Figure 4). Thesemodels are of great
diagnostic andtreatment planning potential forcases with developing
teeth, impac-tions, skeletal malocclusions need-ing orthognathic
surgery, andsevere asymmetries.5,6 They let theclinician see the
patient’s full dentaland skeletal structures, not just thecrowns
like traditional stonemodels. This helps in both thevisualization
and quantification ofexactly where an impaction ordeveloping tooth
is situated, forexample, to the exact depth andorientation, which
allows forunparalleled precision in treatmentplanning for
orthodontic alignmentor surgical extractions. Inorthognathic
surgeries, the exactprocedure can be planned outvirtually by
segmenting the boneas intended and then movingthe segments to the
desiredend point. Furthermore, usingstereolithography, surgical
guidescan be manufactured based onthe treatment plan to guide
thesegments into the predetermined3D placement during the
actualsurgery. 3D models of the dentitionderived from CBCT scans
containnot only the crowns of teeth, butalso their roots and any
tooth thatis developing or impacted and outof reach of traditional
impressiontechniques. They can be used fortraditional measurements
likeoverjet, overbite, arch lengthanalysis, and even more
complexmeasurements like exact rootangles, 3D orientations using
x,y,zcoordinates, and volumemeasurements.5,6 With each
toothindividually segmented, they canalso be moved independently
fromthe others and therefore usedfor virtual orthodontic
treatment
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Figure 3. Panoramic reconstruction of a cone beam computed
tomography scanusing Invivo5 3D imaging software (Anatomage).
3D CEPHALOMETRICS: THE NEW NORM
setups and simulations in a dynamicfashion (Figure 5). The
technologyalso exists for these virtual setupsto be correlated to
indirect treat-ment bonding devices so that thevirtual treatment
plan on the virtualpatient can be connected to the reallife patient
in the operatory.
Superimposition
Successive CBCTscans of a patientcan be superimposed together
toshow the difference between two
Figure 4. A three dimensional digitalstudy model created from a
cone beamcomputed tomography scan using theAnatoModel service
(Anatomage). Thisstudy model, unlike traditional stonemodels, shows
not only the crowns, butalso the roots of teeth, the alveolarbone,
the impactions, and developingteeth.
Alpha Omegan � Volume 103 � Number
time points. This adds the dimen-sion of time into the data,
elevatingit from a single 3D image toa 4-dimensional image
composedof multiple scans at different times.This has been shown to
beextremely valuable for the assess-ment of pre- and
postoperations,such as orthognathic surgery and or-thodontic
treatments, to showgrowth and development, or totrack the healing
or breakdown ofosseous tissues (Figure 6).5,7,8
Figure 5. An AnatoModel (Anatomage) of a mment and growth
simulation. The original Anaposition of the simulation is shown to
thedynamic nature of cone beam computed topieces can be segmented,
modeled, and simtions, and patient education.
2
Using superimposition, anotherdimension can be added, and thatis
the dimension of function. UsingCBCT scans to show functionalchange
between scans is considered5-dimensional imaging, becausethere is
the addition of functionand time above and beyond the ini-tial 3D
CBCT image. This can bevery beneficial for seeing functionalchanges
in airway as a result of man-dibular position change via surgeryor
mandibular advancement devicesfor sleep apnea treatment.7,8 It
canalso be used to show the functionalrange of the mandible by
scanningthe patient in both open andclosed positions.5 With these
typesof superimposition capabilities, theera of static radiology is
historyand a new era of dynamic imaginghas arrived (Figure 7).
3-Dimensional Cephalometrics
Despite the astonishing nature ofCBCT images to provide a
complete3D radiograph of the patient, 3Dcephalometrics has not yet
been
ixed dentition case showing a full treat-toModel is shown to the
left and the endright. This is a classic example of the
mographic imaging in which individualulated for treatment
planning, predic-
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Figure 6. A superimposition of an orthognathic pre/postoperative
analysis using twocone beam computed tomography scans to illustrate
the 4-dimensional change overtime. The full 3-dimensional volume
rendering is shown to the right for completevisualization. To the
left are the axial, sagittal, and coronal slices. Images
createdwith the Invivo5 3D imaging software (Anatomage).
Figure 7. A superimposition of a temporomandibular disease
patient that wasscanned in both the open and closed position to
show the full functional range ofthe mandible. This is an example
of 5-dimensional imaging; the two added dimen-sions are time and
function. The full 3-dimensional volume rendering is shown tothe
right for complete visualizations. To the left are the axial,
sagittal, and coronalslices. Images were created with the Invivo5
3D imaging software (Anatomage).
3D CEPHALOMETRICS: THE NEW NORM
54 Alpha
widely used in the same systematicway and extent that
2-dimensional(2D) cephalometrics has achieved.This should not be
confused withbasic 3D measurements, which areused routinely with
CBCT imagesin orthodontic cases, many of whichare of a
cephalometric nature. Whathas been lacking is a full
systematicmethod, like the standard 2D cepha-lometric images are
traced and ana-lyzed. The vast majority of CBCTimages taken for
orthodontics actu-ally undergo a backwards step intechnology, in
what is called a tradi-tional cephalometric reconstruction.The
reconstruction of a cephalomet-ric image is performed by first
orien-tating the CBCT scan frontally orlaterally and then
flattening all ofthe structures together in an algo-rithm called a
‘‘Ray Sum,’’ whichbasically renders the full volumetricdata into a
flat 2D image9
(Figure 8). It should be noted thatthe ability to reconstruct
traditionalimages is a great power, because anendless number of
reconstructionscan be created from one CBCTscan. However, the trend
should beto not rely on these earlier 2D dis-torted forms and move
on to full3D volumetric visualizations andanalysis. Included in
this trendshould also be the accurate cross-sectional slices, such
as axial, sagit-tal, coronal, and custom slices thatare free of the
magnifications anddistortions that are found in
lateralcephalometric and panoramic im-ages.9,10 Concerning
cephalometricanalysis, there are many reasons forthe 2D
cephalometric reconstruc-tion regression; however, the twomost
common are the lack ofclinical research dealing with
3Dcephalometric analysis systemsbecause of its novelty and,
moreimportantly, an easy computersoftware tool to do this in
Omegan � Volume 103 � Number 2
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Figure 8. A lateral cephalometric recon-struction from a cone
beam computedtomography scan with an iCAT machine(Imaging Sciences
International).Reconstructed cephalometric imageslose their
3-dimensional nature; how-ever, they can still be superior
tostandard cephalometric images in thatthere is no magnification
distortion.Image created with the Invivo5 3D imag-ing software
(Anatomage).
Figure 9. An image of a 3-dimensional cephalometric tracing with
the 3D Cephalo-metric Analysis module for the Invivo5 software
(Anatomage).
3D CEPHALOMETRICS: THE NEW NORM
a clinically efficient way. In April2009, Dr. Heon Jae Cho paved
theway for this to change by laying thefoundations of 3D
cephalometricswith his publication of ‘‘A three-dimensional
cephalometric analysis’’in the Journal of Clinical
Orthodontics.However, it was performed usingsoftware tools that
were too labori-ous and manually intensive for regu-lar clinical
practice.10 Taking intoconsideration that not everyone canperform
such a painstaking task,especially in a clinical situation,a new 3D
cephalometric tracingand analysis software program hasjust been
created by Anatomage tosolve these issues. This new softwareallows
the clinician to trace on theactual 3D volume itself
withoutregressing into 2D cephalometric
Alpha Omegan � Volume 103 � Number
reconstructions in a very fast andefficient manner with full
analyticcapabilities (Figure 9). In so doing,it provides new 3D
measurementsand data derived from the standardcephalometric
landmarks, whichcan be automatically located withsimple tracing
techniques. In addi-tion, these new 3D measurementscan be
correlated to standard 2Dmeasurements for validation
withaccumulated past research. Theclinician can create any 3D
land-mark, any measurement betweenlandmarks, and then
systematicallytrace and analyze the data accordingto their own
methods, all in threedimensions. This efficient and easyto use tool
will usher in a new eraof full 3D cephalometrics, and
willeventually become the new norm towhich the standard is
held.
CONCLUSION
CBCT machines and associated3D imaging software packages
2
have now been in use for approxi-mately 10 years. Their use
steadilyincreases, and the applications areexpanding. Both hardware
andsoftware developments are quicklybeing created, deployed, and
usedby academic institutions, imagingcenters, and private
practicesaround the globe. The academiccommunity is very active in
CBCT-related research and developments,and more are yet to come.
The mainprinciples and applications havebeen established through
scores ofpublications in each specialty, withthis article focusing
on some ofthe salient features of CBCT imag-ing in orthodontics and
dentofacialorthopedics. The potential for clini-cians to visualize
and measure withperfect accuracy the completeand complex 3D
structures of thepatient’s craniofacial morphologyis extremely
beneficial, and necessi-tated in some complex cases for themost
accurate and advanced
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3D CEPHALOMETRICS: THE NEW NORM
orthodontic diagnosis, treatmentplanning, and posttreatment
as-sessments. These techniques andothers are currently
beingpracticed all over the world andare continually being
developedand perfected. It is the responsibil-ity of each clinician
in their respec-tive fields to know what CBCTimaging can do for
their patientsand when they should use it,when they do not need to
use it,and most importantly, when theymust use it. The standards of
diag-nostic care are quickly changing indentistry as a result of
CBCT imag-ing, and it is crucial for dentists tobe up to date with
these trends bybeing avid readers of publicationsthat elucidate how
3D CBCTimaging is changing the face ofdentistry.11
56
References1. Periago DR, Scarfe WC, Moshiri M,
Scheetz JP, Silveira AM, Farman AG.
Linear accuracy and reliability of cone
beam CT derived 3-dimensional images
constructed using an orthodontic volu-
metric rendering program. Angle
Orthod 2008;78:387–95.
2. Stratemann SA, Huang JC. Comparison
of cone beam computed tomography
imaging with physical measures. Dento-
maxillofac Radiol 2008;37:80–93.
3. Lascala CA, Panella J, Marques MM.
Analysis of the accuracy of linear mea-
surements obtained by cone beam com-
puted tomography (CBCT-NewTom).
Dentomaxillofac Radiol 2004;33:291–4.
4. Broadbent BH. A new X-ray technique
and its application to orthodontia.
Angle Orthodontist 1931;1:45–66.
5. Chenin DL, Chenin DA, Chenin ST,
Choi J. Dynamic cone-beam computed
tomography in orthodontic treatment.
J Clin Orthod 2009;43:507–12.
6. Mah J. The evolution of digital study
models. J Clin Orthod 2007;41:557–61.
Alpha
7. McCrillis J, Farman A, Scarfe W, Haskell
J, Brammer M, Chenin DL. Segmenta-
tion of the airway using CBCT in ob-
structive sleep apnea with and without
placement of mandibular advancement
device. Int J Cars 2008;(Suppl 1):
S208–10.
8. McCrillis JM, Haskell J, Haskell BS,
Brammer M, Chenin DL, Scarfe WC,
et al. Obstructive sleep apnea and the
use of cone beam computed tomogra-
phy in airway imaging: a review. Semin
Orthod 2009;15:63–9.
9. van Vlijmen OJ, Maal T, Bergé SJ, Bronk-
horst EM, Katsaros C, Kuijpers-Jagtman
AM. A comparison between 2D and 3D
cephalometry on CBCT scans of human
skulls. Int J Oral Maxillofac Surg 2010;
39:156–60.
10. Cho HJ. A three-dimensional cephalo-
metric analysis. J Clin Orthod 2009;
43:235–52.
11. Curley A, Hatcher DC. Cone beam
CT—anatomic assessment and legal
issues: the new standards of care. J Calif
Dent Assoc 2009;37:653–62.
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3D Cephalometrics: The New NormHistorical 3-Dimensional
PerspectiveDynamic Cone Beam Computed Tomography Study
ModelsSuperimposition3-Dimensional Cephalometrics
ConclusionReferences
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