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).

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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

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(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.

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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.

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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

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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

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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

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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

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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

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metric rendering program. Angle

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2. Stratemann SA, Huang JC. Comparison

of cone beam computed tomography

imaging with physical measures. Dento-

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3. Lascala CA, Panella J, Marques MM.

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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,

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tomography in orthodontic treatment.

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models. J Clin Orthod 2007;41:557–61.

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7. McCrillis J, Farman A, Scarfe W, Haskell

J, Brammer M, Chenin DL. Segmenta-

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8. McCrillis JM, Haskell J, Haskell BS,

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9. van Vlijmen OJ, Maal T, Bergé SJ, Bronk-

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Omegan � Volume 103 � Number 2

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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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