CBCT IN ORTHODONTICS

Cone Beam Computed
Tomography
PRINCIPLES & APPLICATIONS IN ORTHODONTICS
DR HADIA ARSHAD

CONTENTS
 Introduction
 CBCT vs. CT
 Principles of use
 Advantages, Disadvantages & limitations
 Errors in CBCT
 CBCT dosimetry
 Guildlines for the use of CBCT
 Clinical indications of CBCT
 Advanced applications of CBCT in orthodontics
 Conclusion
 References

Evolution
Discovery of x-
ray in 1895
First digital
dental
panoramic x-
ray system 1995
Development
of computed
tomography
Multislice CT
and CBCT

Dr. Otto Walkhoff took the first
intraoral radiograph in early
1896

TOMOGRAPHY
TOMOGRAPHY: Imaging of Layer/Slice
SLICE/CUT: The cross section portion of body which is scanned for production of CT or CBCT
image

Cone Beam Computed Tomography
A medical imaging technique consisting of X-ray computed
tomography where the X-rays are divergent, forming a cone.
With rapid 180 degree or more ( most frequently 360 degree) , a
CBCT provides essentially immediate and accurate two
dimensional (2D) and three-dimensional (3D) radiographic images
of an anatomical structure.

First CBCT scanner was
built for angiography at the
Mayo Clinic in 1982.

COMPARISON
CONE BEAM COMPUTED
TOMOGRAPHY
Cone shaped x-ray beam
Lower radiation dose
Shorter scan time
One or two rotations
Flat panel 2D detector
Isotropic voxels
Can be manipulated on personal computers
Relatively smaller equipment
Comparatively less cost
Voxel size smaller
Streak artifacts less likely
COMPUTED TOMOGRAPHY
Fan shaped x-ray beam
Higher radiation dose
Longer scan time
Several rotations
Several rows of circular detectors
Anisotropic voxels
Supplied as hard copies
Large equipment
Higher cost
Larger voxel size
Streak artifacts

Patient Position
Imaging may be performed with the
patient seated, supine, or standing.
The patient’s head is positioned and
stabilized between the x-ray generator
and detector by a head holding
apparatus

Components used:
X-ray
generator
Image sensor
Image
reconstruction

X-ray generator
High voltage generator which modifies incoming
voltage and current to provide the x ray tube with
the power needed to produce an x ray beam of
desired peak kilovoltage (kVp) and current (mA)
o X ray tube
o Anode
o Cathode
o Tube envelop
o Tube housing
o Collimator
Exposure factors can be controlled manually or
automatically
◦ • KVp 60 to 90
◦ • mA 6 to 10
◦ • Pulsed or continuous x ray generation

Procedure
1. A 3D cone beam is directed through a
central object onto a detector.
2. After a single two-dimensional
projection is acquired by the detector,
the x-ray source and detector rotate a
small distance around a trajectory arc.
3. At this second angular position another
basis projection image is captured.
4. This sequence continues around the
object for the entire 360 degrees.

Scan time
• Average time for one cbct scan may vary from 7-30 seconds.
• It also varies if half a rotation or a full circle rotation is used.
• Standard scan- 3-4 seconds, lower resolution.

CBCT Image Reconstruction
During a CBCT scan, many single 2D snapshot images are captured from predefined
angles as the machine moves through a single isocentric rotation of the x-ray
source/sensor unit
These raw images are then computationally compiled into a 3D dataset with the use of
specialized reconstruction algorithms. The volume is often referred to as the “3D
image,”

Acquisition Stage
a CBCT scan consist of a sequence of 2D projection images
Projection data
Transferred via Ethernet
connection
Processing computer
(workstation)

Reconstruction Stage
The basis images are processed which includes correction of the images both visually and
geometrically and final application of a reconstruction algorithm.
Once all slices have been reconstructed, they can be recombined into a single volume for
visualization. (3d image)
Reconstruct the projection data to provide standard viewing layouts in three orthogonal
planes—frontal (sagittal), lateral(coronal) and superior (axial)

CBCT provides two features for orthodontic practice:
◦ 1) linear (lateral and postero-anterior cephalometric images) or curved
planar projections (panoramic images) can be derived from a single
CBCT scan;
◦ 2) CBCT data can be reconstructed to provide unique images
previously unavailable in orthodontic practice

The first commercial CBCT system for oral and maxillofacial
imaging was the NewTom,whichwas first approvedby the
Food and Drug Administration (FDA)in April 2001, and is
currently in its fourth generation as the NewTomVG.

Multi Planar Reformatting (MPR)
Refers to reformatting images at a nonorthogonal or oblique orientation
Several anatomic structures are not particularly well visualized and represented as
displayed in the sagittal and/or coronal planes, and MPR can be useful in these
instances.
The orientation of this formatting is viewer derived and can be
◦ Linear oblique (useful for temporomandibular joint assessment)
◦ Curved oblique (providing a “panoramic” image) or
◦ Serial transplanar

Multiplanar
Projections
A, An axial view produced at the
level of the mandibular dentition.
B, A midsagittal plane
reconstruction.
C, A coronal section through the
premolar region of jaws.
D, A sequenceof transaxial views of
the left premolar region. Selected
anatomy has been labeled as
follows: NF, nasal fossa;IC, incisive
canal; SS, sphenoid sinus; MS,
maxillary sinus; Palate, hard palate;
MF, mental foramen; MC,
mandibularcanal.

Volumetric Vision/Visualization
Volumetric vision refers to the approaches that can be applied to visualize 2D
data in a 3D mode.
1. Variable slice thickness viewing.
2. Maximum intensity projection (MIP)
3. Minimum intensity projection
4. Indirect volume rendering
―Surface, shaded or volume rendering

Maximum
intensity
projection
(MIP)
Used to highlight features
The anatomic features associated
with the brightest pixel or voxel
intensity are projected on the
display screen.
This method creates a high
contrast image, but the brighter
pixels/voxels may mask or
superimpose over less bright
pixels, thus potentially hiding
important anatomic features.

Shaded
Surface
Rendering
Shaded-surface rendering is
useful for high-contrast
imaging such as bone.
This rendering techniques
allow the operator to set a
pixel or voxel intensity
threshold that excludes
structures lower than the
selected threshold and
renders all structures greater
than the selected threshold.

Maximum
intensity profile
and surface
rendered
reconstructions

Volume
Rendering
Creates a three dimensional
model using no pixel/voxel
threshold for data exclusion
The entire volume is always
loaded, but tissues are grouped
interactively by voxel intensity,
and each group can be assigned
a color and transparency value
before projecting the volume
onto the viewing monitor.
To understand the anatomic
relationships between
structures visually

Characteristics For An Ideal CBCT Image
For Diagnosis
• Good density and contrast
• Sharpness
• Good resolution
• Accuracy of image
• Free of artifacts
• Free of noise

Where did the X in X-ray come
from?
A german physicist, wilhelm roentgen, discovered a new
form of radiation in 1895. He called it x-radiation because
he didn't know what it was. Yes, it's as simple as that.
This mysterious radiation had the ability to pass through
many materials that absorb visible light.

Field of view
The FOV is a cylindrical or spherical volume and
determines the shape and size of the reconstructed image
It refers to the area of the anatomy that is captured by the scan
Collimation of x ray beam by adjustment of FOV limits the radiation to one ROI.
FOV depends on:
◦ The detector size and shape,
◦ Beam projection geometry
◦ The ability to collimate or not
◦ Size of the individual

Protocol For The
Selection Of
Appropriate
Field Of View
The choice of the FOV is
based on the diagnostic
objectives for the imaging as
determined through a
careful clinical assessment
of the patient.

FOV Ranges Most Commonly Used In
Orthodontic Imaging

Pixel
MATRIX
The CT image is represented as the Matrix of the number.
A two dimensional array of numbers arranged in rows and columns is called a
matrix
Each number represent the value of the image at that location.
PIXEL:
Each square in a matrix is called a pixel.
Also known as picture element.

Voxel
3D images are composed of voxels instead of pixels used in 2D
digital images.
The size of each voxel is deter mined by its height, width, and
thickness
Is the smallest element of the 3D radiograph image volume
Detectors with smaller pixel size capture fewer x-ray photons per voxel and result in
more noise.
Smaller the voxel size, higher the resolution

Resolution
The ability of an image to differentiate between two closely placed objects.
Two types
◦ Spatial resolution
◦ Contrast resolution
Spatial resolution – the ability to visualize the difference between two objects of
different radio density
Contrast resolution – ability to differentiate two objects of the same color type.

Greyscale
The ability of a cbct scan to display differences in
attenuation.
This parameter is called bit depth of the system and
determines the number of shades of grey available to
display the attenuation.
All current CBCT machines have 12 bit detectors and are
capable of identifying 4096 shades of gray .
A 16 bit detector can identify 65,536 shades of grey

DICOM File
Cbct produces two data products
◦ The volumetric image data from the scan
◦ Image report generated by the operator
All of these images are save in the DICOM (digital imaging and communication
in medicine) format.
This is the international standards organization –referenced standard for all
diagnostic imaging. Includes x ray, visible light images and ultrasound etc.

Effective Dose
The effective dose is used to compare the stochastic risk of non-uniform exposure to
radiation.
To allow a meaningful comparison of radiation dose, and thus risk, radiation exposures
are frequently converted to effective doses
Measured in sieverts (sv or milli- [msv] or micro-sv)
The radiation dose to specific tissues is measured, adjusted for amount of that tissue in
the field of view, and weighted based on radiation sensitivity of the tissue. The
weighted tissue/organ doses are then summed to produce the effective dose.

Effective Doses of Imaging Examinations
Used in Orthodontics

Factors That Influence The Radiation Dose
and Risk Estimation
BIOLOGICAL FACTORS
• Higher Risk in children (smaller and cellular growth)
TECHNICAL FACTORS
• Exposure time
• The imaging parameters used (kvp, amps);
• Current and exposure time are directly proportional to dose
• Pulsed beam versus continuous beam;
• Pulsed reduces exposure time and hence the dose
• Amount, type, and shape of beam filter;
• Higher filtration reduces exposure
• Full 360° rotation versus lesser rotation;
• Limited versus full field of view
• Resolution

The average annual natural background
radiation is 3000 microSv/yr

Methods To Reduce Radiation Dose
◦ Using smaller field of views
◦ Use of high voltage and beam filtration
◦ Shorter exposure time
◦ Using pulsed exposure
◦ Low contrast to noise ratios
◦ Low resolution

ADVANTAGES
• Rapid scan time- reduces motion artifacts
• Beam limitation through collimation reduces and limits the radiation to the ROI
• Image accuracy
• Better image with high resolution image due to small voxel size (0.07-0.25)
• Interactive display modes
• Multiplanar reformatting (to provide optimal visualization from different angles
and perspectives)
• 3 dimensional volume rendering
• Economical, comfortable and safe
• Data can be used in other diagnostic, modeling, and manufacturing application

ADVANTAGES
• 3D representation of dental and craniofacial structures;
• Custom image reformatting to provide optimal visualization from different angles
and perspectives;
• Orthogonal images that do not contain magnification errors or projection artifacts
• Management of superimpositions;
• Interoperability in digital imaging and communications in medicine (DICOM) format;
• Generation of data that can be used in other diagnostic, modeling, and manufacturing
applications; and
• Radiation exposure within a similar range of other dental radiographic imaging
devices, which is generally an order of magnitude lower than that of medical CT
devices.

DISADVANTAGES
• Scatter
• Artifacts
• Motion artifacts due to increased scan time
• Scan volume insufficiency
• Poor contrast resolution, thus soft tissue cannot be viewed
• Image noise is detrimental

LIMITATIONS
• Poor soft tissue detail limits the use for assessment of these tissues
• Radiological interpretation can be difficult when using a smaller field of view
• Cone-beam technology based on an image intensifier may allow the periphery of the
image to be distorted.
• Patient movement can limit the technique for very young children, those unable to
stay still or with movement disorders
• Rapid changes in both hard- and soft-ware technology, which can render publications
outdated
• Streak artifacts due to restorations
• Very small lesions (smaller than voxel size) can not be discerned
• Supine positioning of the patient during scanning with some machines may alter the
position of the facial soft tissues
• There may be difficulty in identifying anatomic landmarks with some cone beam
units due to lack of fine details

ARTIFACTS
INHERENT
ARTIFACTS
Scatter
Partial volume
averaging
Cone beam effect
PROCEDURE
RELATED
ARTIFACTS
Striations
Patient movement
artifact
INTRODUCED
ARTIFACTS
Beam hardening
Cupping artifact
Extinction or missing
value artifact

SCATTER Results from x ray photons that are diffracted from their original path after
interaction with matter. The scattered photons that are captured by the
sensors contribute to over all image degradation called ‘quantum noise’
PARTIAL
VOLUME
AVERAGING
When the selected voxel size of the scan is larger than the object being
imaged. Boundaries in the resultant image may have a step appearance or
homogeneity of pixel intensity level.
CONE BEAM
EFFECT
Because of the divergence of the x ray beam as it rotates around the patient in
a horizontal plane, structures at the top and bottom of the image are exposed
only when the xray source is on the opposite side of the patient. This results
in large Image distortion and streak artifacts and peripheral noise
INHERENT ARTIFACTS

PROCEDURE RELATED ARTIFACTS
Striations/
Patient
movement
artifact
When very few basis images are taken or the time
between the images are too long, under sampling of the
object can occur.
This leads to aliasing artifacts or striations in the image.

INTRODUCED ARTIFACTS
Beam
hardening
As an x-ray beam passes through an object , lower energy photons are absorbed in
preference to higher energy photons. This is called beam hardening , which results
in two types of artifacts,
i. Distortion of metallic structures as a result of differential absorption known as the
cupping artifact
ii. Streaks and dark bands which when present between two dense objects create
extinction or missing artifacts

GUIDELINES FOR THE USE
OF CBCT IN ORTHODONTICS

PATIENT SELECTION FOR CBCT
•The ALARA principal must always be applied.
•There should be justification of the exposure to the patient so that the total
diagnostic benefits are greater than the individual determinant the radiation
may cause.
•Should be used only when a Periapical or an OPG cannot provide necessary
information for patient diagnosis and treatment planning.

Proposed
algorithm for
selecting
radiographs for
the patient
receiving
orthodontic care.

GUIDELINES
1. History and clinical examination
2. Benefits should outweigh risks
3. New information to aid the patient
4. Not be repeated routinely
5. Diagnosis with lower radiation
imaging is questionable
6. Thorough clinical evaluation report
should be made
7. Should not be done for soft tissue
assessment
8. Use small volume doses where you can
9. Resolution compatible with adequate
diagnosis yet low radiation
10. Small FOV for dento-alveolar regions
and teeth
11. Avoiding the use of CBCT solely to
facilitate the placement of orthodontic
appliances such as aligners and
computer-bent wires.

CONTENTS
Introduction
CBCT vs. CT
Principles of use od CBCT
 Advantages, Disadvantages & limitations
Errors in CBCT
CBCT dosimetry
Guildlines for the use of CBCT
 Clinical indications of CBCT
 Advanced applications of CBCT in orthodontics
 Recent Advances
 Conclusion
 References

CBCT application-related
to dental specialties

Missing teeth
Impacted teeth &
Ectopic teeth
Supernumerary
teeth
Dental
development and
eruption sequence
Tooth size
measurements
bolton , arch
perimeter
Root abnormalities Cysts, tumors etc Implant placement
Expansion Facial asymmetry
Craniofacial
syndromes e.g.
CLP
Facial trauma

CBCT
recommendations
in Orthodontics
according to the
European
SedentexCT (2012)
guidelines

Dental Development/Tooth
Morphologies
Cone beam computed tomography scan can be
used to evaluate developing arch length
problems.
Small to medium FOV recommended.
Evaluation of:
◦ Presence or absence of Unerupted teeth
◦ Tooth development
◦ Tooth position
◦ Bone loss & formation
◦ Bone depth, height and width
◦ Proximity of adjacent teeth
◦ Amount of bone covering the teeth

Dental
morphology and
development
visualization
in a mixed
dentition case

Tooth
Morphology
Example of an ectopic rotated
Unerupted right central incisor
with a dilacerated apex.
Example of a markedly ectopic upper
left canine causing severe resorption of
the upper left central incisor root.

Missing teeth
Missing tooth. The patient lost the
left upper lateral incisor several
years previously.
The CBCT images show thin
alveolar bone width, thus further
bone grafting was needed before
placement of a dental implant

Impacted Teeth
Most common indications for CBCT imaging in orthodontics.
Small to medium FOV
3D images permit clear visualization of the location and relationships of the impacted
canines

CBCT image showing panoramic view

CBCT images showing the relationship of the impacted canine
with adjacent teeth

Impacted canines in 3D reconstructed views

Impacted
Canines
Volumetric views of
impacted canines and their
positional relationship to
adjacent teeth in both
maxillary and mandibular
arches (A)
Frontal and (B and C) oblique
views to better visualize the
impacted canine crown (B)
and its root

Supernumerary teeth
CBCT can help in localization of these supernumerary teeth , giving the diagnostic
process the added advantage of buccolingual evaluation of each individual section
without superimposition of the adjacent teeth and structures.

Supernumerary
teeth
Axial cross-section through
the maxilla in a 7-year-old
child. The cleft is clearly seen
on the right side (small
arrows). There are several
other dental anomalies
present including a
supernumerary tooth located
buccal to the upper right
central incisor crown (large
arrow).

Supernumerary
teeth
Supernumerary tooth. A
mesiodens (*) was
impacted medially to the
right upper deciduous
central incisor and
palatally to the right
upper central incisor.

Root Abnormalities
◦ CBCT provides enhanced visualization of roots, making it a
valuable tool for assessing preorthodontic or post-orthodontic
root resorption.
◦ The mean difference between direct and radiographic CBCT
measurements of root length has been shown to be 0.05 mm (SD
± 0.75).
◦ CBCT has been shown to be better than OPG in determining
root angulations,
◦ In contrast, CBCT is at least as good as periapical radiography
for assessing root and tooth length.

Root Abnormalities
• CBCT provides accurate assessment of alveolar bone height, but because CBCT
had a high number of false positives in the determination of fenestrations

Orthodontic appliances produce lesser
artifacts than dental restorations but may
interfere with the views of dental occlusal
anatomy

External Root
Resorption
29-yearold man who had
external root resorption on
the upper incisors.
Those teeth also had thin
facial and palatal alveolar
bone coverage over the roots.

Root
Fractures
This 26-year-old male
patient has an apical third
root fracture with a
negative response to
electric pulp test.

Cyst and Tumors
Mostly accidental findings.

Simple bone
cyst
The left mandible from
canine to third molar region
appears radiolucent without
any trabeculation.
The cbct images show
radiolucency within the
mandible without
trabeculation

Multiplanar reformats in the (A) axial,
(B) coronal, and (C) sagittal planes of a third molar impacted due
to a dentigerous cyst

ABCESS
A 19-year-old female
patient complained of
pain and purulent pus
discharge on the left
upper first molar during
her orthodontic treatment.
The involved tooth had
periapical alveolar bone
resorption and facial
alveolar bone loss
(dehiscence).

ODONTOMA
9-year-old boy whose
complaint was delayed
eruption of the upper left
incisors.
CBCT images revealed
several toothlike
structures that looked like
a deformed tooth over the
impacted upper left
incisor teeth.

Alveolar Boundary conditions
• Thin alveolar bone around roots.
• Allows the orthodontist to make better treatment decisions
• Volumetric analysis- assess cortical bone thickness in planned areas of Ortho-
gnathic surgical cuts/splits.

Cross-sectional view of a
patient with a deep overbite.
The maxillary incisor apex is
approximating the dense
maxillary cortical bone and
any attempts for intrusion
would significantly increase
the risk of root resorption.

Left and right
tooth-pair
analysis
To compare root torque
and symmetry of tooth
inclination.
verify the positions of the
roots relative to the buccal
and lingual cortical plates
of alveolar bone support

Cross section of a mandible in the molar
region to assess cortical bone thickness, which may be
especially useful in the prediction of favorable or
unfavorable splits during treatment planning for
orthognathic surgery cases

TMJ Disorders
◦ TMJ may be visualized in volumetric views as well as sectional views.
◦ Developmental and pathologic changes can be detected using the lateral
views.
◦ Large FOV allows visualization of adjacent structures, such as the stylohyoid
ligaments, cervical spine and other anatomic regions that may be responsible
for referred pain to the TMJ.
◦ Functional shifts can occasionally be detected

Transcranial
TMJ views
The CBCT of an 18 year-
old female patient shows a
growing condyle with
many porous cavitation's
on the condylar head
surface

Cleft lip and palate
 Numbers, quality, and location of teeth in proximity to the cleft site
 The eruption status and path of canines in grafted cleft sites
Accurate assessment of the size and volume of the bony defect
 Estimates the amount of bone required to repair the defect.

3D volumetric reconstructions of a patient with
bilateral CL/P

CLP
The left cleft palate
extends into the left nasal
cavity (A).
The CBCT images of bone
and face show bone
defect, smaller upper
dental arch, retruded
maxilla. Facial profile after
surgical correction can be
recorded

Airway Assessment (OSA)
 Major improvement in the airway analysis, allowing for its 3D and volumetric
analysis.
 Evaluation of airway patency or obstruction is often a factor in deciding
between orthodontic and orthognathic therapies

Researchers who used specialized software found sleep apnea patients had a
smaller anterioposterior dimension (mm) of the minimum cross section segment
and smaller minimum cross section area positioned always retropalatal, compared
with control patients. There were no significant differences in upper airway
volume between the 2 groups

A virtual
representation of a
complete airway
passage
(nasopharynx,
oropharynx, and
hypopharynx)
segmented from a
CBCT DICOM
dataset

Implant (TAD) Placement
 CBCT allows for visualization of the inter proximal root space, palatal cortical bone
thickness, sinus morphology, and other critical structures for proper selection of TAD
length.
 In addition, assessment of bone density is possible from the volumetric data which
allows selection of an ideal site for placement of TADs.

TADs-
Anchorage
planning
Two palatal mini-implants
for orthodontic anchorage.
The posterior mini-implant
perforated the palate but was
covered with mucosa

Orthognathic Treatment Planning
CBCT offers
 Refined diagnosis and optimized treatment objectives in 3D
 Virtual treatment planning to improve surgical procedures and
outcomes
Evaluates 3D virtual models pre and post surgery for assessment of
maxillo-mandibular anatomy and position

Virtual surgical treatment
planning for a patient to
visualize and determine
the magnitude of
maxillary and mandibular
movements, as well as any
complication such as
proximal segment
interferences that may
arise during surgery.

The results of a CBCT study showed that the amount of
surface swelling reduces approximately by 60% in
individuals within a month after surgery.
Bimaxillary jaw surgery produces a greater amount of
swelling but reduces at a faster rate than single jaw surgery.

Craniofacial Morphometrics
• For analysis of the size, shape and volumetric
differences in bilateral structures as well as growth
changes in 3D.
• Refined and quantifiable diagnoses in all three planes
of space that may be clinically significant enough to
alter treatment planning decisions.

Facial Asymmetry
 3D CBCT imaging in the diagnosis and treatment planning of asymmetries, where
discrepancies often manifest in all three planes of space.
 When large differences exist between bilateral structures, CBCT scans enable the use of
a technique called “mirroring”
 In which the normal side is mirrored onto the discrepant side so as to simulate and
visualize the desired end result, as well as to plan the surgery to facilitate correction
(Metzger et al ., 2007)

Mirroring on a mid-sagittal plane for quantitation
of mandibular asymmetry

Facial Asymmetry
LIMITATION OF MIRRORING
Mirroring using mid-sagittal plane generates inaccurate and clinically irrelevant results
for patients
◦ Cleft palate with facial features that affect the midline position of the points (NA, ANS, ba)
used to define this plane.
◦ In patients with asymmetries involving the cranial base, registration on the cranial base also
results in suboptimal results.

To also always look for Occult
Pathologies

Accidental Findings
Enostosis, condensing osteitis, dense bone island, and focal apical osteopetrosis are
radiopaque lesions noted near the apices of teeth and which appear to have no etiologic
causative factors.
IMPLICATIONS
◦ These lesions may prevent tooth movement but may
◦ Not readily visualized on a panoramic radiograph.
◦ Space closure or establishment of proper root tip or torque may not be possible and if
biomechanical forces are applied to move the adjacent tooth against the dense lesion,
external apical root resorption will likely result.

Patient with enostosis in the
interradicular area between
the lower right second
bicuspid and first
molar.

REPORTING OF CBCT
The complete dataset must be evaluated.
It is imperative that the reporting dentist is adequately trained for this
role.
Small field of view scans can be reported by a dentist who has
undergone further training.
However, the larger field of view scans that include the sinuses, TMJs,
base of skull and the cervical spine should be reported by either a
dentomaxillofacial radiologist or a general radiologist with a interest in
head and neck imaging

ADVANCED APPLICATIONS OF
CBCT IN TREATMENT PLANNING

3D CEPHLALOMETRICS
LATERAL CEPHALOGRAM
 With CBCT, projectional magnification is computationally corrected during primary
reconstruction, creating an orthogonal images.
 If a left and right side asymmetry exists, it is possible to generate a lateral
cephalometric view of each side for independent analysis.
 Advantages include the ability to excise extraneous anatomical structures, thereby
eliminating superimpositions

3D CEPHLALOMETRICS
PA CEPHALOGRAM
◦ The major advantages of CBCT-generated frontal cephalograms are 2-
fold:
◦ the ability to perform volume operations or
◦ the ability to reposition the head into an ideal position in all 3 planes of space before
generation of a posterior-anterior cephalogram.

CBCT derived DPT
◦ The panoramic view of the dentition from CBCT is similar to a
traditional panoramic x-ray but is remarkably clearer because there is
no superimposition of the spinal column and the contra lateral side.
◦ In addition, there are no projection artifacts, such as the burnout area
often observed in the anterior region

Alveolar Ridge Shape and Volume
◦ Evaluation of Dento-Alveolar arch form.
◦ Use of CBCT occlusal images to select arch wire forms.
◦ Arch form tracings are typically made at the height of the alveolus
◦ Other uses:
Arch-length measurements
Bolton analysis.

Facial Analysis
• New software features now enable facial photos (either 2D or 3D) to be
morphed onto a DICOM dataset
• 3D volume can generate a simulated 3D projection of the face in any frontal,
lateral, or user-defined view of the face.
• By changing the translucency of the image, one can determine the specific
relationship of the soft tissues to the skeleton
• This has significant implications in the planning of tooth movements,
orthognathic surgery, or other craniofacial therapies that could alter facial
appearance.

Stereo photogrammetry Superimposition
These images maybe overlaid on one another on known structures to determine the surface
changes and to correlate them to growth

Facial photos superimposed onto a 3D volumetric
skeletal rendering

3D Superimpositions
• The goal of 3D superimposition of serial images is to understand how changes
in size and shape and shifts in relative positions of skeletal and soft tissue
facial components contribute to orthodontic/orthopedic or surgical treatment
changes.
• The first step in the registration process is to determine which structures will be used as a
stable reference.
• The displacement, change in shape, or in size will be later described relative to these structures.

Superimposition of
2 structures and
quantitative
color-mapping
enables the
comparison of 3D
objects at different
time points to
assess longitudinal
growth

Color maps of
soft tissue
changes

MODEL
SUPER-
IMPOSITIONS
Tooth movement changes.
Registration of pre- and
posttreatment digital models
using the palatal rugae.

Virtual Models
3D study models of the dentition now can
be obtained by intra- and extraoral imaging
technologies.
CBCT imaging offers study models that
display individual crowns and roots.
.

Advantages of VDMs
• Diagnostic information of
• Root position,
• Root shape,
• Bone level,
• Internal dental anatomy,
• Relationship to anatomic structures
• Quantitative bone density information.
◦ Ease of access,
◦ Digital storage (which requires little physical space),
◦ Ease of transfer to colleagues and insurances or other offices, among
◦ Crown to root ratios can be estimated
◦ Tooth measurements can be performed even before the teeth erupt.
◦ The virtual “dental setup” now also includes the roots, which allow for torque
and labiolingual inclination in the “dental setup.”

3D PRINTING OF VIRTUAL RECORDS

Summary of Clinical Application Of
Virtual Records
Facial
Growth
Craniofacial
Anomalies
Orthognathic
Surgery
Creation of
Study
Models from
CBCT
Images

Capabilities Of CBCT Software's
. One-click cephalometric image;
One-click panoramic image;
Onscreen models with secgmented teeth;
Visual treatment objective capability;
Onscreen articulator;
Ability to superimpose DICOM files;
Auto-cuts (eg, click on impacted maxillary canine and see diagnostic cuts which can be “fine-tuned”);
Pathology cuts;
Affordability;
Ability to measure the teeth;
Bolton analysis;
Virtual extraction;
Ability to move the teeth;
Idealized setup; and
Fabricate appliances

Treatment planning with
CBCT
CASE REPORTS

CASE REPORT-1
Chief complaint:
Narrow smile &
crooked teeth
A) 45° upward smiling view of the
patient’s 3 showing the narrow
buccal segments and “dark
corridors
B) coronal cross-section of cone
beam CBCT scan through the
bicuspid area, showing the
lingual inclination of these teeth
and the proximity to the cortical
bone
C) Fuller smile with upright
posterior buccal segment
D) CBCT scan showing more upright
posterior segments and the
location of the roots into the
alveolar bone

CASE REPORT-2
Boundary
condition
a 46-year-old woman with
complaint of painful lump in
buccal vestibule maxillary right
premolar region

ULTRA LOW DOSE CBCT
Developed for CBCT studies, producing multiple CBCT data files with decrease number
of the original projection views

Ultra low dose image - Orthodontic case
Planmeca ProMax 3D Classic - FOV Ø 40 x 50 mm. - Voxel size 150 µm - Effective patient dose 14.4 µSv

Ultra low dose image - Airways
Planmeca ProMax 3D Max - FOV Ø 230 x 160 mm. - Voxel size 600 µm - Effective
patient dose 21 µSV

THE FUTURE
PROBABLY, NEXT ITERATION OF DIGITAL INVENTION INTO THE FIELD OF
RADIO DIAGNOSIS WILL BE THE DEVELOPMENT IN ARTIFICIAL
INTELLIGENCE BASED IMAGING DIAGNOSIS.

MESSAGE OF THE DAY
Its not about perfection. Its about
effort, and when you bring that effort
every single day, that’s when
transformation happens.

Summary
Usefulness if 3D imaging in Orthodontics:
To aid in diagnosis and treatment planning;
◦ Assessment of arch length and tooth size discrepancy
◦ For evaluating different treatment options
◦ Anchorage planning
◦ Evaluation of expansion, uprighting and IPR
◦ To evaluate effects of different treatment plans on the face in three dimensions
◦ To visualize of end of treatment goals
◦ Treatment monitoring
◦ Communication and patient education
◦ For planning outcomes of Orthognathic surgeries
◦ For printing models and casts

IN CONCLUSION
3D imaging is a useful adjunct to 2D imaging in selected cases
This technique hugely expands the fields for diagnosis and treatment possibilities, not to
forget many more research frontiers as well.
However CBCT should be used with careful consideration ,it should not be used where
2D imaging suffices.

SOURCES
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• White and Pharrow , oral radiology edition 6, 2009
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CBCT IN ORTHODONTICS

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