Recent advances in diagnostic aids 2 /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
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Magnetic Resonance
Imaging
A type of emission
imaging
Essentially imaging of
water in the tissue


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Magnetic Resonance Imaging
Principle


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When images are displayed; intense
signals show as white and weak ones as
black .
Intermediate as shades of gray.
Cortical bone and teeth with low presence
of hydrogen are poorly imaged and
appear black.

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MRI can clearly differentiate the soft
tissue components
Preferred imaging technique when
information regarding the articular disc or
the presence of adhesions,or joint effusion
is desired


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Indications

Assessing diseases of the TMJ
Cleft lip and palate
Tonsillitis and adenoiditis
Cysts and infections
Tumors

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Contraindications
 Patients with cardiac pacemakers.
 Patients with cerebral metallic aneurysm clips.
Slight movement of the clip could produce
bleeding
 Stainless steel and other metals produce
artifacts ; obliterate image details of the facial
area.

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Shortcomings
Inability to identify ligament tears or

perforations
Dynamics of tissue joint not possible
Cannot be used in patients suffering from
claustrophobia.

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3D Imaging
Historical perspective


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3D Imaging
Necessity
- Our pts. are 3D therefore we
need to record their morphology
in 3D
- Drawbacks of cephalometrics
2 dimensional representation
of a 3 dimensional object


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3D Imaging

With dimensionally accurate records, not only
can t/t be planned and simulated,but
implemented through methods such as
computerized wire bending & fabrication of
appliances by CAD/CAM
Development of future technologies and
approaches to Orthodontics

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Basic principles of 3D imaging
Two main geometrical strategies
1. Orthogonal measurement
2. Measurement by triangulation
1. Orthogonal – Location of 3rd dimension(z) by a
technique separate from that used to measure the other
two dimensions.(x & y)
- Object sliced in layers – physically or optically

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Basic principles of 3D imaging
2. Triangulation
Images captured from two positions


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Methods of 3D Facial Imaging

LASER (Light Amplification by Stimulated
Emission of Radiation)
Structured light
Laser scanner
- Scanner record distortion
of projected laser pattern on
the face to provide a’ surface map’

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- Simultaneously image is recorded by a digital
-

camera
This image is layered over the surface map


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Structured Light
- Projection of a structure of lines or grids onto the face
- As the projected pattern is distorted by the contours of
face, this distorted pattern is recorded by a digital
camera


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Obtaining 3D Dental Models
Destructive scanning
Non destructive scanning
Destructive scanning
- Variant of orthogonal slicing method
- Study cast is invested in a solid matrix of
contrasting colour
-Surface of the block is then sliced parallel to
the occlusal plane
- Laser scan of the 2D surface is made
- An additional 0.003” layer of the block is ground
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away and another scan is made

Obtaining 3D Dental Models
Non destructive scanning
- Laser stripe is projected on the surface of
plaster cast and distortion pattern is recorded by
a digital camera


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3D Craniofacial Skeletal Imaging
Anatomic Reconstructions
Computed Tomography Scans
Cone Beam Computed Tomography


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Anatomic Reconstructions (CRIL Method)
- Integrated 3D model of the craniofacial
structures is formed using lat.&fro. ceph;
photographs & 3D models of dental casts.
- Equipments – i. Calibrated stereo x ray device
ii. Calibrated stereo camera
iii. 3D models of study casts from Align
Technology

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• Step 1 – generating 3D

dental models of upp &
low teeth and creating Tiepoint bearing aligners
- Tie points are reference
points (like implants of
Bjork) which facilitates
merging of images

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• Step 2 – placing facial Tie points

• Step 3 – generating a 3D photographic
model of the face


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• Step 4 – generating a 3D x ray model of
the craniofacial skeleton


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• Step 5 - Merging the several 3D models
- The CRIL software is used to merge the
data in a single frame of reference
- At least 3 common tie-points are required
in each overlapping


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• Step 6 – Viewing the integrated 3
Dimensional model

The resulting 3D craniofacial model is viewed
interactively using Align’s TREAT software


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Computed Tomography Scans
- Post processing software allows for
reconstruction of transverse slices in any plane


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Cone Beam Computed Tomography
- Like conventional CT but various modifications are done
to optimize them for craniofacial imaging
- Reduced chamber volume just enough for head and
neck
- Real time feed back betn sensor and X ray source
- Cone beam projection of x rays

- Radiation exposure – 20%of conventional CT
- Precision of 0.28mm which 5-10 times more

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Softwares for Orthodontics
• Many companies have developed softwares to

help the Orthodontist in diagnosis and treatment
planning
- Dentofacial planner
- Vistadent
- Sure smile
- Dr.Ceph
- Digiceph
- eModels
- OrthoCAD

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OrthoCAD
Diagnosis
Space analysis
Treatment simulations- tooth movement,extn,occlusal contacts


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Invisalign
• What is invisalign?

- Invisible alignment of the teeth
- An invisible way to align the teeth
• Uses a series of clear removable
aligners to straighten teeth without
metal wires or brackets.
• Developed by Align Technology,CA

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Impressions
are made
using
Polyvinyl
Siloxane

After wearing all of
the aligners in the
series,

Impression and
bite send along
with a detailed
treatment plan.

advanced imaging
technology
transforms plaster
models into a
highly accurate 3-D
digital image.

A computerized movie called ClinCheck® depicting the movement
of teeth from the
beginning to the final
position is created.

Procedure

customized set of
aligners are made from
From the approved file,
these models, sent to the
laser scanning to build a
doctor, and given to the
set Invisalign® uses of
patient. Pt to wear each
actual models that reflect
aligner for about two
each stage of the
weeks. www.indiandentalacademy.com
treatment plan.

Using the Internet, the
doctor reviews the
ClinCheck file - if
necessary, adjustments
to the depicted plan are
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made.

Invisalign


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Invisalign
Patient gets the first aligner 6 weeks after
the 1st visit
Most treatments require 20 – 60 aligners
 Worn for 2 weeks each
Should be taken off only for eating and
brushing


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Invisalign
• Limitations
Patients with severe malocclusions cannot
be treated
Children,mixed dentition – growing jaws
and erupting teeth too complicated for the
computer to model
No precise control over root movements

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References
• T M Graber,Vanarsdall R L : Orthodontics-Current
•
•
•
•
•
•

Principles and Techniques.
Putman C E, Ravin C E : Textbook of Diagnostic
Imaging.
Jacobson : Radiographic Cephalometry
Goaz,White : Oral Radiology – Principles and
Interpretation.
Harring J I, Jansen L : Dental Radiography- Principles
and Techniques
Pasler F A : Colour Atlas of Radiology.
Kapila & others : Craniofacial Imaging in Orthodontics :
Historical Perspective,current status,and future
developments. Angle Orthod, 1999; 69:491-506

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• J J Menig. The DenOptix Digital Radiographic System.

JCO,1999; 33: 407-410.
• Seminars in Orthodontics, December 2001,Vol 7 No 4 :
1. Baumrind, Boyd : Integrated Three Dimensional
Craniofacial Mapping: Background,Principles and
Perspectives
2. Hans et al : Three Dimensional Imaging : The Case
Western Reserve University Method.
3. O C Tuncay: Three Dimensional Imaging and Motion
Animation
4. J Mah, A Bunman: Technology to create Three
Dimensional Pt. Record.
5.Curry,Baumrind : Integrated Three Dimensional
Craniofacial Mapping at the Craniofacial Research
Instrumentation Laboratory/University of the Pacific.
6. W R Redmond : The Digital Orthodontic Office:2001.

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• Websites :

www.cril .org
www.acuscape.com
www.orthocad.com
www.3dmetrics.com
www.aligntech.com
www.gendexxray.com
www.dentalmodels.com
www.zerobase-usa.com
www.minolta3d.com
www.orametrix.com
www.geodigmcorp.com


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Recent advances in diagnostic aids 2 /certified fixed orthodontic courses by Indian dental academy

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