3D Facial Imagining /certified fixed orthodontic courses by Indian dental academy

RECENT ADVANCES
IN DIAGNOSTIC AIDS

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacdemy.com
www.indiandentalacademy.com

3 D FACIAL IMAGING
THE CUTTING EDGE


• Principles of 3d imaging
• Over view of different techniques
Stereophotogrammetry
3d laser scanning
3d cephalometry
3D facial morphometry
Moire topography
3d cone beam ct scanning
• Applications of 3d imaging

3D FACIAL IMAGING


3 D DENTAL IMAGING


PROCESS OF ACQUIRING 3 D
IMAGE

• In 3D medical imaging set of
anatomical data is collected using
diagnostic imaging equipment.


IMAGE

• Then processed by a computer and
then displayed on a 2D monitor to give
an illusion of depth.


IMAGE

• Depth perception causes the image to
appear in 3D.


Applications of 3D imaging
• Pre post orthodontic assessment of dento-skeletal and
facial relationships.
• Auditing orthodontic outcomes in regard to soft and hard
tissue.
• 3D treatment planning
• 3D soft and hard tissue simulation
• 3D customized arch wires
• Archiving 3D facial,skeletal and dental planning for in
treatment records.
• Research and medico legal purpose are also benefits of
3D imaging.

Historical background
• Singh and Savara ( angle orthodontist
1966) 3D analysis of maxillary growth
changes in girls.
• Thalmann and degan ( 1944) reported
the use of stereophotogrammetry.


PRINCIPLES


STEPS IN 3D IMAGING


MODELLING


TEXTURE MAPPING


Shading and lighting


RENDERING


APPROACHES TO 3D IMAGING
• Udupa and Herman ( 3d imaging in
medicine 1991).


SLICE IMAGING


VOLUME IMAGING


PROJECTIVE IMAGING


MEASURING SCANNED OBJECTS
• Orthogonal measurement

• Measurement by triangulation


ORTHOGONAL MEASUREMENT
Y

Z
X


MEASUREMENT BY
TRIANGULATION


VARIOUS TECHNIQUES
•
•
•
•
•
•

3D Cephalometry
3D CT scanning
3D laser scanning
Moire topography
Structured light technique
Stereophotogrammetry


3D CEPHALOMETRY
• Drawbacks
– Time consuming
– Exposes the patients to radiation
– Does not define soft tissue and there are
difficulty in relating accurately the same
landmarks in two radiographs ,especially in
biplanar technique.


3D LASER SCANNING
Advantages –
Less invasive technique for capturing
face for planning or for evaluation
outcomes of treatment.


Disadvantages –
- slowness of method, making distortion of
scanned image likely.
- safety issues of exposing eyes to laser
beam, especially in growing children.
- inability to capture soft tissue texture, which
results in difficulties in identification of
landmarks that are dependant of surface
color.

Moire topography
• Defines 3D information based on the
contour fringes and fringe intervals.
• Difficulties are encountered if the
surface has sharp features.
• Care to be taken about positioning of
the head.


• Motoyoshi et al ( AJO 1992)
described the system and concluded
that it does not capture facial texture
and subsequent landmark identification
is difficult.


STRUCTURED LIGHT TECHNIQUE
• Light is used to illuminate the scene
and only one image is required.
• The position of the illuminated points in
the captured image compared to their
position on the light projection plane
provides the information to extract the
3D co-ordinates of the imaged object.


DRAWBACKS
• To obtain high density image the face
needs to be illuminated several times
with light.this is time consuming and
may alter the position of the head.
• Also the camera does not provide a
1800 ear to ear facial model.


• Techaletpaisarn and Kuroda (Int J Adult
Orthod Orthog surg 1998)
Used two Lcd projectors and Ccd ,and
computer to produce a 3D image.


• Curry et al ( seminar in orthodontics
2001) their system consists of 2
cameras and a projector.
• Texture mapping


STEREOPHOTOGRAMMETRY
• Two cameras configured as a stereo
pair are used to recover 3D distances of
features on the surface of face by
triangulation.


• Uses a portable stereometric camera
along with a plotting instrument .
• Recent advances have enabled
conversion of simple photographs into
3D images.


• Ras et al ( journal of dentistry 1996 )
demonstrated a stereophotogrametric
system that gives 3D co ordinates of
any chosen facial landmarks that can
be measured
• Consists of 2 synchronized semi metric
cameras mounted on a frame with a
difference of 50 cm and a position
convergently with an angle of 15
degrees.

C3D IMAGING SYSTEM
• This is based on use of special digital
cameras and with a special textured
illumination ,with a capture time of 50
milli seconds and is sufficiently cost
effective to be used in daily practice.


• It captures the natural surface
appearance of patients skin and drapes
this texture on the captured 3D model
of the face.
• It offers a life like3D model that can be
rotated tilted and angulated like a
patients head.


3D FACIAL MORPHOMETRY
• Uses 2 CCD cameras that capture the
subject
• real time hardware for recognition of
markers
• software for 3D reconstruction of
landmarks.


• Landmarks are located with a 2mm
hemisphere reflective markers.
• An infra red streptoscope is used to
light up the reflective markers.
• Two side acquisiton is required to
capture the whole face.


DRAWBACKS
• Placement of landmarks on the face is
time and labour consuming
• Reproducibility of landmark is
questionable.
• No life like models are produced to
show natural soft tissue appearance of
the face.


APPLICATIONS OF 3D FACIAL IMAGING
• Assessment of facial deformity and outcome
of surgical and/or orthodontic correction.


• Subjective outcome of deformities, 3D models
are a valuable media for locating the source
of deformity and its magnitude.


• Assessment of outcome can also be
performed easily by visual comparison of pre
and post treatment models placed side by
side.


LAND MARK BASED
SUPERIMPOSITION


3D CT SCANNING
• Surgical outcome and soft to hard
tissue ratio following orthognathic
surgery (Mccance et al BJO 1992)


OPTICAL LASER SCANNING
• Used to assess soft tissue changes
following functional treatment (Morris et
al EJO 1998)
• Following extraction and non extraction
treatment (MORRIS et al AJO DO
2002)
• Following orthognathic surgery (Moss et
al AJO DO 1994)
• Cleft lip and palate (Mccance et al Cleft
Craniofac J 1997)

STEREOPHOTOGRAMMETRY
• Assess the outcome of twin block
treatment (Bourne et al Clin Orthod
2001)
• Combined orthodontic surgical
treatment of class II or class III (Hajeer
et al Int J Adult Orthod Orthognath
2002)


3D FACIAL MORPHOMETRY
• Application in orthodontics and allied
fields (Ferrario et al Plast Reconstr Surg
1999)


RESULTS OF FACIAL CHANGES
•
•
•
•

Landmark identification
Inter landmark distance and angles
Color millimetric maps
Volumetric changes


3D Dental Imaging


3D LASER SCANNING
• Difficult procedure

• Safety issues


3D LASER SCANNING OF STUDY CASTS


APPLICATIONS OF 3D IMAGING OF THE
TEETH

Archiving study models (Orthocad)


VIRTUAL ORTHODONTIC PATIENT


• Combining 3D skeletal ct scan with
vision or laser scanning techniques.


XIA TECHNIQUE (IJO 2000)
• Reconstructing 3D soft and hard tissue
models for sequential CT slices using a
surface rendering technique
• Three colouerd potraits (different
colours) were texture mapped onto the
3D mesh
• Validity of construction was not
evaluated nor was the importance of
head postioning

3D CT SKELETAL MAPS AND 3D
LASER MODELS
• Nishi et al and Terraai et al (JOMS
1997)


3D SKELETAL DATA WITH 3D
LASER SCANNING
• Okumura et al (AJO DO 1999)
• This cannot be used for prediction of
soft tissue changes following treatment.


3D CEPH DATA WITH 3D LASER
SCANNING
• Chen and chen
(Int J Adult Orthod Orthognat Surg
1999)
• 3D computer aided simulation system to
plan surgical procedures an to predict
post operative changes in orthognathic
surgery patients

3D SPIRAL CT SCAN AND
STEREOPHPTOGRAMMETRY
• Khanay et al (Int J Adult Orthod
Orthognat Surg 2002)


CRANIOFACIAL RESEARCH
• Tie points( landmarks placed on speific
areas of the face prior to imgaing).
• Anatomic areas marked on the x ray act
as refrence points.


Teleradiology
• Teleradiology is the electronic
transmission of radiological images
from one location to another for the
purposes of interpretation and/or
consultation


• When a teleradiology system is used to
produce the official authenticated
written interpretation,- there should not
be a significant loss of spatial or
contrast resolution from image
acquisition through transmission to final
image display.


RECENT ADVANCES
IN DIAGNOSTIC AIDS

Dr. Sathwik. B. S.


3D cone beam c t scan


Conventional c t scan
• Developed by Godfrey hounsfeld (1967)

• Different generations based on
organization of the individual parts of
the device and physical motion of the
beam of capturing the data.

First generation
• Single radiation source and a single
detector.
The information obtained by slice and
slice.


Second generation
• Multiple detectors within the plane of
scan.
• These were not continuous nor did they
scan the diameter of the object.


Third generation
• Advancement in data acquisition and
detector
• Fan beam ct.
• Ring artifacts were seen on the image
often distorting the 3D image and
obscuring certain landmarks.


Fourth generation
• A moving radiation dose and a fixed
detector ring were introduced.
• More scattered radiation were seen.


Fifth generation
• To reduce motion or scatter artifacts.
• The detector is stationary and electron beam
is swept along a semi circular tungsten strip
anode.
• The radiation is produced where the electron
beam hits the anode and this results In an x
ray that rotates about the patient without any
translation or scatter.
• 4D motion picture

limitations
• Considerable physical space.


limitations
• Much more expensive.


limitations
• Stacking procedure (time consuming
and expensive).
• Radiation exposure was primarily
responsible for limiting its usage.


CBCT (cone beam CT scan)


• Developed to overcome some of the
limitations of conventional ct scanning.


Procedure
• Object is captured by a 2 d detector so
that a single rotation can capture the
area of interest
• Cone beam also produces less
scattering of radiation.
• Radiation exposure is 20% of
conventional c t ( equal to full mouth
IOPA)

Advantages of CBCT
• Reduction in the cost


Advantages of CBCT
• Smaller in size
• Exposure chamber (head) is custom
built and reduces the amount of
radiation


Advantages of CBCT
• Images are comparable to conventional
c t and are displayed as full head view
or regional components.


• CBCT machines are available for
different size,possible settings,area of
image capture and field of view.


Acquisition systems
•
•
•
•

New tom 3 g (quantitative radiology Italy)
I cat ( imaging sciences international USA )
C b mercury ( Hitachi medical corp., japan)
3 d acuitomo ( J morita mfg corp. ).


New tom 3 g
• Image capture is done in 36 sec.
• Voxel resolution of .125mm.
• They can be incorporated into dicom 3
d software for analysis.


I cat
• 20 – 40 sec image
capture time
• Field view of 20 x 25
cms can be obtained .
• Amorphous silicon flat
panel detector
produces no distortion.


Cb mercury ray
• Image intensifier and a solid state ccd.
• Gives 288 views in 10 sec .


3 d accuitomo
• Field of view 30x40 mm focuses on
regional and anatomical investigations
• Small size ( 1.6 times an OPG unit ).


Clinical applications


Impacted teeth


Airway analysis
• Aboudara et al (orthod craniofac 2003)
• Showed variability in the upper airway
space compared with lateral ceph.


Assessment of alveolar bone height
and volume
• Hatcher et al ( 2003) site for implant
placement.


Lateral and frontal cephalometric
views


Advantages over other cephalograms
• True 1:1 representation of the structure
being imaged.
• Avoiding superimposition of irrelevant
structures.


3 d skeletal views


3 d facial analysis


Alveolar ridge shape and volume


3 d review of dentition


TMJ analysis


Radiation exposure
• Depends on the kvp and ma.


Alara principle
• Radiographs on the patient needs
• Using the fastest film compatible with
the diagnostic task
• Collimating the size of the beam to as
close o film size.
• Using lead aprons and thyroid shields.


Drawbacks
• Map out the muscle structures and their
attachments
• True colour texture of the skin cannot
be captured
• Long capture time of the full view of a
subject ( 30 –40 sec).
• High costs


Resorption of incisors after ectopic
eruption of maxillary canines:
a CT study
• Angle orthodontist 2000 (Sune Ericson
and Kurol)


Superimposition of 3D cone beam CT
models of orthognathic surgery
patients
• British journal of radiology 2005
(Bailey et al)


MRI scan


• Formerly called as NMR ( nuclear
magnetic resonance )
• Primarily used to demonstrate the
physiological or pathological alterations
in living tissues.


History of MRI
• Developed by Dr. Raymond Damadian
and a group of graduate students at
downtown medical centre.
• First performed in July 1997.
• Paul Lauterbur and sir Peter Mansfield
were awarded the Nobel prize in 2003.


•
•
•
•
•
•

What is an MRI scan
How does a MRI scanner work
What does a MRI scan show
When are MRI scans done
How is an MRI scan done
Difference between an MRI and CT
scan
• Risks and safety issues concerning an
MRI scan www.indiandentalacademy.com

What is a MRI scan?
• Is a radiological technique that uses
magnetism, radio waves and a
computer to produce images of body
waves.


How does a MRI scanner work
• Radio waves 10,000 – 30,000 times
stronger than the magnetic field of earth
are sent through the body.
• Body produces radio waves of its own.
• Scanner picks up these signals and a
computer turns them into an image.


What does an MRI scanner show
• It is possible to
make pictures of
all body
structures.
• Less hydrogen
atoms (darker).
• More hydrogen
atoms (brighter).

• It is possible to get clear pictures of
body that are surrounded by bone
tissue (brain and spinal cord).
• Best technique to find out tumors
especially of the brain .
• MULTIPLE SCLEROSIS (BLEEDING)
and lack of oxygen or stroke.


When are MRI scans used
•
•
•
•

Brain tumors
Integrity of spinal cord after trauma.
Structure of the heart and aorta.
Accurate information of the joints, soft
joints and bones inside the body.
• Surgeries can be accurately directed
after MRI.

Dental applications
• Relation of orthodontics and TMD
(Temperomandibular disorders).
• Post treatment
• Results of orthognathic surgeries.
• Effects of mandibular advancements in
obstructive sleep apnea.


How is an MRI scan performed?
• Out patient procedure
• Patient needs to relax.
• All metallic objects need to be removed
before the scan
• Remove all hearing aids or pace
makers.


• Loud clicking noises are heard which
may be uncomfortable for the patient.
• Iv injections are necessary to enhance
the images


• Water
• Paramagnetic contrast compound
(gandolium compound)
• Super-magnetic contrast agents (iron
oxide nano particles)
• Diamagnetic agents (barium sulphate)


Safety procedure
• Implants and foreign objects


Ferromagnetic foreign bodies
• Shell fragments
• Metallic implants


Reactions
• Trauma due to movement of objects in
magnetic field
• Thermal injury
• Failure of an implanted device


Projectiles
• Missile effect accidents ( attractions of
ferromagnetic objects towards Center of
magnet)


Radiofrequency energy
• Hyperthermia in children.


Acoustic noise
• 130 db ( jet engine take off)
• Appropriate use of ear protection


Cryogens
• Emergency shut down of
superconducting magnet leads to an
operation called quenching.
• Release of helium and risk of
asphyxiation.
• Recommissioning of magnet is
extremely expensive


Is MRI scan dangerous
• There are no known side effects.
• Within first 12 weeks of pregnancy.
• Because of large cylinder the procedure
may be claustrophobic.


Specialized MRI scans
• Diffusion MRI scanning
- diffusion tensor imaging
- diffusion weighted imaging
• Magnetic resonance angiography
• Magnetic resonance spectroscopy
• Interventional MRI
• Radiation therapy stimulation
• Current density imaging

Applications of MRI scanning


MRI of pharynx and treatment
efficiency of mandibular advancement
in OSPS
• Eur resp j 2002 (Sanner et al )


Orthodontics and TMD
• AJO DO 2002 (Grabber et al )


Frankel appliance therapy and TMD
• AJO DO 2002 (Franco et al )


Rigid versus wire fixation for
mandibular advancement
• AJO DO 2002 (Dolce et al )


Changes in condylar disc position and
tm after disc repositioning therapy
• Angle orthodontist feb 2000 (Hatice and
Turkharmann)


RECENT ADVANCES
IN DIAGNOSTIC AIDS


Thank you
Leader in continuing dental education


3D Facial Imagining /certified fixed orthodontic courses by Indian dental academy

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