Diagnostic aids in orthodontics /certified fixed orthodontic courses by Indian dental academy

DIAGNOSTIC AIDS IN ORTHODONTICS-2

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

DIAGNOSTIC AIDS IN
ORTHODONTICS-2
•
•
•
•
•
•

Kesling diagnostic set up.
Xeroradiography.
Electromyography.
Occlusograms.
Holograms.
Digital- 1)cameras, 2)models


KESLING DIAGNOSTIC SET UP
• Proposed by H.D.Kesling.
• Individual

teeth

&

their

associated

alveolar

processes are sectioned off and replaced on model
base in the desired position.
• Helps in simulating various tooth movements.


.
• Horizontal cut-using
fretsaw blade 3mm
apical to gingival
margin.
• Vertical
cuts
to
separate teeth.


Uses
1) Visualizing and testing effects of complex tooth
movements and extractions on the occlusion.
2) Patient motivation.
3) Tooth size - arch length discrepancy can be
visualized.


Xeroradiography
• Developed by Chestor.F.Carlson in 1937.
• Records images without the need of film.
• Dry non chemical process which makes use of
electrostatic process.
• 2 typesa) Medical 125-in general radiography.
b) Denta 110 – Dental xeroradiography.

Technique
• Made on selenium coated aluminium plates.
• Selenium when given a positive or negative
charge is photosesnsitive ant the charge is altered
by exposure to x-rays-Latent image
• Development is by blowing fine electrically
charged powder over exposed plate.
• Image is then transferred from plate to paperVisible image
• If selenium is positive charged-areas of greatest
density are displayed as dark blue,
• Negative charged-light blue or white
• Can be reused as many as 1000 times

Advantages
1) It can be viewed without transillumination.
2) Serial xeroradographic tracings can be applied
directly over original head film thereby reducing
tracing error.
3) Edge enhancement effect-intraosseous detail
&soft tissue boundary definitions are superior.
4) Teeth are more readily visualized in negative
mode,intraosseous
structures
in
positive
mode.Soft tissues are represented equally in
both.
5) Cephalometric landmarks are easily identified.
6) Reconstruction of cephalometr planes &points
can be made directly.

Disadvantage
• Because of expense of leasing the processing
system use of xeroradiographic head film is not
practical in orthodontic office.


ELECTROMYOGRAPHY
• Defined as recording of &study of intrinsic
electrical properties of skeletal muscle by means
of surface or needle electrodes.
• Quality better with needle electrodes.
• Surface electrodes are non invasive & decreased
risk of infections.
• Robert & Moyers-first to use E.M.G.
• Pancherz (1980) found decreased E.M.G. activity
of masseter &temporalis muscle during chewing
in class II divI subjects-attributed to diverging
dentofacial morphology &unstable occlusal
contact

• Moyers (1949)studied E.M.G.s of children with
class II div I –found temporalis muscle
dysfunction in habitual occlusion &at rest.
• Winders et al (1958)studied forces exerted on the
dentition by perioral &lingual musculature during
swallowing &found increased muscle activity in
tongue thrust group.
• E.M.G. is a valuable diagnostic toola) determine etiology of malocclusion,
b) response of orofacial musculature to
orthodontic therapies
c) helps in research

OCCLUSOGRAMS
• It is a 1:1 reproduction of the occlusal surfaces of
plaster models on a sheet of acetate tracing paper.
• A central groove cut into backs of both models
can be used for orientation.

Grooves can be cut by a
custom made dental cast
scriber or a triangular
file.


• Dr.Charles Burstone developed an occlusogram
camera assembly-4“x 5“box camera,a dental cast
stage,2 flood lights&a hinged plexiglass plate.
• A 210 mm lens is used to produce 1:1
magnification
• Disadvantage-Expensive & scarce equipment


• Another technique to produce occlusalgrams was
by orthoscan camera.
• The depth of field of this camera is almost nil, and
the central orientation groove on the backs of the
models is apt to be distorted and inaccurate.
• Third technique: Use of a copying machine to
copy the occlusal surfaces of the dental casts.
Disadvantage:
Images are enlarged by as much as 10% depending
on the machine used, so clinical accuracy may be
seriously undermined with this technique.

• The most premitive technique
for making occlusal grams is
to trace the occlusal surfaces
of the teeth onto a clear 1/8”
plastic sheet.
• Since the eye of the viewer is
the camera, the viewer’s head
must not be moved while
tracing both sides of the
model.

Procedure
• To make standard photographs of the occlusal
aspects of the dental casts, the occlusogram
camera assembly consists as a 4 by 5 inch box
camera, a dental cast stage, two 375-watt
floodlights, and a hinged Plexiglas plate.
• To produce 1:1 magnification, a 210 mm lens is
found to be satisfactory.
• Each dental cast is placed on dental stage and is
brought up to the leading edge of the stage.
• Registration dots which are located in the
leading edge of the stage will also be recorded
on the occlusogram.

• With a fine-grain positive film placed into the film
cassette, and with both floodlights focused on the
dental cast, a typical exposure of 4 seconds at f45
is made.
• Processed according to manufacturer’s directions,
maxillary

and

mandibular

occlusograms

produced at 1:1 magnification.


are

Tracing of occlusal gram
• Acetate paper is placed
over the occlusograms and
the
maxillary
and
mandibular
teeth
are
outlined, showing the
gingival tooth contours,
incisal edges, buccal cusp
ridges, central grooves,
and cusp tips. Also traced
are the palatal rugae, the
midpalatal raphe, the fovea
palatinus,
and
the
registration dots.

Orientation of occlusogram

• Midsaggital
and
transverse
registration lines are constructed.
• Midsagittal – by connecting the
incise papilla.
• Transverse – Is constructive distal
to the last molar in the arch and
perpendicular to the midsagittal
registration line.

• The maxillary and mandibular
occlusogram tracings are then
separated.
• Assembled using the registration
dots
and
the
maxillary
registration lines are duplicated
on the mandibular occlusogram
tracing.
• Both pieces of tracing paper,
when oriented can be thought of
as the maxillary and mandibular
denture bases in centric relation
at the beginning of orthodontic
treatment.

Typical ideal normal Class I occlusogram

1) The biting edge of the upper anterior teeth lies in front of
the biting edge of the lower anterior teeth by an averaged of
.7mm (anterior overjet).
2) The upper posterior teeth extend beyond the lower posterior
teeth by an average of 2.3mm on each side (posterior
overjet)
3) The upper bicuspids are wider than the lower bicuspids by
an average of 1.9mm on each each side (bicuspid lateral
overjet).
4) The upper molars www.indiandentalacademy.com lower molars by an
are wider than the
average of1.4mm on each side (lateral molar overjet)

Clinical significant of Occlusograms
1) Individualised arch forms
2) Arch length Discrepancy Measurement:
By
superimposing the idealized lower arch form on
the original.
3) Occlusal simulations: It permits the orthodontists
to quickly see if the maxillary teeth even have the
possibility of occluding with the lower correctly.
• Also to judge if the teeth will fit together without
mesiodistal alteration.
Tuverson (1980) and Andrews (1976) have suggested
that improper torque and / or tip on the anterior teeth
will limit available arch length, space for proper
occlusion is lost.

•

So when ideal occlusograms are designed with
1mm of anterior overjet, one is assuming correct
tip and torque for the incisors too.

4) Evaluation of Various Treatment Plans:
• With occlusograms, the orthodontist can try any
alternative he can think of without risk of harm to
the patient.
• Since the anteroposterior position of the denture
bases is influenced by growth, facial growth
rotations, changes in the cant of the occlusal plane,
and/or surgery, these positions should be
anticipated for the period of treatment and
incorporated into the occlusogram tracings.

Holograms:
• Holography is a photographic technique for
recording and reconstructing images in such a way
that 3D aspect of an object can be attained.
• The recorded image is called a “Hologram.
• The theory of holography was first developed by
Garbor in 1948, and the first hologram was
produced by Leith and Upatnieks in 1964.
• Holography is a wave front reconstruction process
in which two coherent beams converge to produce
constructive and destructive intereference pattern
which is recorded in film.

• Laser is needed to produce a hologram
• A hologram can record all the information
contained by dental casts and also can be used for
direct measurement. The storage of many dental
casts for several years can be eliminated if a
working duplication of all the information from
the casts can be put on a single holographic film.
• A developed hologram contains all of the target
information. If the hologram is cut in half, each
half contains a complete image; if subdivided
further, each small piece still contains a complete
image but at some sacrifice of resolution and
image quality.

Recording of Hologram

• The laser beam passes through the film first, thus
acting as the reference beam and is then reflected
back on to the film as the object beam.
• Laser beam used is helium-neon of 25mW power
• The Holographic film used is 4 x 5 inch Kodak
holographic film with high resolution.
• A film is held within two optical quality glass plates
of 2.5mm thick which keeps the film absolutely flat
and firm.
• The orthodontic study models are placed beneath
these glass plates and as close as possible to them but
without touching.

• It is important not to have any external or internal
vibrations affecting the system, as a movement of
even half the wavelength of light will affect the
quality or ever totally destroy the image.
• It can be minimized by keeping all the components
of the system on the one optical bench so that such
movement is then applicable to each component
and is thus negated.


Processing Technique of Hologram
• The films are exposed in semi-darkness and are
best developed by treating immediately as the latent
image may fade within 24 hours.
• They have special emulsions whose particle size
has been refined down to one-twentieth the
wavelength of light – 30 nm.
• Film is immersed in a dish of developer (Kodak
DX80), with the emulsion side uppermost for 45
seconds at about 20oC
• Removed from the developer and rinsed briefly
under a tap and immersed in fixer/bleach until
clear.
• Washed in running water for about 1 minute and
then dried in methanol.

Orthodontic applications
• Storage of study models
• Measurement of incisor intrusion
• Study of the effects high pull head gear traction in
human children skulls.
• Effect of class-II elastics on bone displacements.
• Effect of cervical pull head gear on maxilla
• Determine centres of rotation produced by
orthodontic forces.
• Lower incisor space analysis
• Prognosis in Franke, theory patients.
• To assess facial and dental arch symmetrics.

Advantages
1) Scratches / dost covering does not interfere with the
latent image.
2) Serial superimposition allows to visualize tooth
movement.
3) The virtual image of holographic record can be
measured accurately in 3D.
4) Reconstruction of images for clinical purpose may
be done using a simple light source.
5) Vast reduction in storage space and used for
medicolegal requirement, where films are stored
with normal medical record.
6) Cost of production is similar to conventional
radiography.
7) Images are clinically reliable and errors are not
clinically significant.

BuscAang et al (J.C.O. 90) in his study compared
cast and occlusal view of hologram. Errors were
found to be consistently greater for the holograms
than for the cast, and the disparity can be minimized
by taking measurements parallel and closer to the
hologram reference plane.

To ensure accuracy

separate hologram from various perspectives would
be required.


• Mc Guinners et al (B.J.O. 1993) found that errors in
the hologram readings were found to be 3 times as
great for study models and when individual
components of PAR were compared significantly
smaller scores were obtained for lower incisor
crowding and midline discrepancy and goes an
indication that PAR index tends to underestimate the
severity of malocclusion when assessed from
holograms as opposed to study models.

• Most of the study shows greater errors in
holographic images than in study cast, so better
refinement is needed to decrease errors and there
by

improving

precision

and

holographic images.


reliability

of

DIGITAL CAMERAS AND ORTODONTICS
• The technique dates back to 1981 – Sony produced
the Mavica, the first consumer level electronic
camera.
• Initially, the quality of images was poor.
• The rapid advancements in digital improvements in
image quality, and in the capacity of computer
hardware to store these images.
• It’s widely used now a days compared to conventional
film photography as
1) Whole process of storage and retrieval is
demanding in both time and space.
2) Risk of pictures being misfiled
3) Deteriorating in quality over time.

Working of Digital Camera
• The image to be recorded to focused onto a grid on
a charge-coupled device (CCD).
• Each cell of the grid is assigned a numerical value,
determined by the average shade and intensity of
colour of the light falling on that cell (pixel).
• Images taken on a digital camera stored within the
memory card analogues to the film in a
conventional camera
• Memory cards can be slotted into a Personal
Computer
Manufacturer
Interface
Adaptor
(PCMIA) or 3.5 inch floppy disk adaptor of a PC
for direct downloading onto the hard disk.

•

Once downloaded the image is usually stored as a
compressed file using one of a number of
internationally agreed standards.

•

The images are then normally stored as JPEG files
(Joint Photographic Experts Group).

•

The size of standard JPEG images – 200-600kB.

•

A single floppy disk will hold approximately 2 to
7 images

•

A CD with 650 MB capacity will hold over 100.

Types of Digital Camera
3 Types
1) Low resolution – these are no longer available
2) Mid-range- generating a file size of approximately
350kB
3) Megapixel – producing files of approximately 600
kB.
The greater the number of pixels, greater the detail
recorded. But increasing the number of pixels
requires more memory.
The camera may also have in LCD color display,
enabling the operator to preview the image before
storage.
Eg: Kodak 120, Nikon Coolpix 900, Olympus C-

•

Quality of Digital photos at present is limited by
following factors.
1) The

optical

resolution

of the

digitizing

mechanism
2) The amount of memory in the camera
3) Resolution of the final output device (eg.
Printer Projector).

If it is less than that

recorded by the camera, then the final quality
of the image will be determined by the
resolution of www.indiandentalacademy.com
printer.

Advantages
1) The images can be instantly reproduced and
poorly composed pictures can be retaken
immediately.
2) Inexpensive
3) No chemical processing is required.
4) Storage and filing is easy
5) Images are immediately ready to transmit
electronically or project using a display tablet or
video projector, no scanning of negatives or prints
is necessary.

Image manipulation
• It is possible to alter the brightness, intensity,
colour tint and sharpness of the image, as well as
adding to add deleting parts of the picture.
• Image manipulation may be accidental or
intentional but innocent, or deliberately
fraudulent
• New encryption systems have been developed to
detect tampering with images, where changes in
the image are identified as changes in a
superimposed coding added at the time of the
original image capture.

Digital Models
• The recent technological advances have allowed the
general of digital dental models that can be saved
and viewed three-dimensionally on a computer.
• The alginate impressions are shipped overnight to
one of the companies offering digital models.
• A traditional plaster model is fabricated and using
CAD-CAM technology, is transformed into a
digital, 3D image of the dentition.
• Within few days a electronic file is available to be
downloaded from the internet to a desired computer
• Once downloaded, the software enables the digital
models to be viewed and manipulated.

Advantages over plaster models
1) Not subject to physical damage
2) Require negligible storage space – 1 set of models
is less than 1 MB in size. A typical 700MB CD-R
holds over 700 cases.
3) Retrieval is fast and efficient
4) No expense of model duplication.
5) Digital models are also in excellent presentation
tool.
6) Simultaneous view of models at one time is
possible.

• The two major computerized model systems
creating digital models are OrthoCADTM (Cadenrt,
Inc, Fairview, NJ) and emodelsTM (GeoDigm, Corp,
Chanbassen, MN)
OrthoCADTM
• First company to introduce a digital model service
in 1999.
• The startup software for OrthoCADTM is free of
charge and is about 8 megabytes in size.
• The cost is approximately same as for a laboratory
charge for a set of trimmed study casts.
• OrthoCAD’s – 3-D browser software allows the
clinician five simultaneous views of the models.

• It
can
also
make
measurement in any plane
of space. E.g., Bolton
analysis, Tanaka Johnson
analysis
• It also features of crosssectional
tool
(Jaws
Alignment Tool) that can
slice the digital models in
any vertical or horizontal
plane
• It also has a occlusogram
feature

OrthoCAD’s Virtual Set-Up enables the clinician to
simulate and visualize any desired treatment option
including
virtual
extractions,
interproximal
reduction, expansion leveling, and to apply various
fixed appliances.


• The
new
innovation
introduced by OrthoCADTM is
their
Bracket
Placement
System
• The clinician places each
bracket in desired position
virtually in the digital model
using bracket placement wand
• It has a miniature video
camera, that transmites high
resolution images of the intra
oral environment

• The system determines the relative position of the
want versus the actual tooth and gives the
practitioner a positioning target and signals when
the virtual placement coincides with the actual
placement
• One of the new innovation currently tested is
centric occlusion – centric relation (CO-CR)
feature in their software


emodelsTM
• Founded in 1996 by GeoDigm as interactive
reflective imaging system
• Software size 12MB compare to 8MB of
OrthoCAD
• More expensive
• Has the facility of simultaneous viewing, tooth
measurement in any plane of space, cross sectional
tool
• The most useful feature is eplanTM – virtual
diagnostic setup

References


Leader in continuing dental education


Diagnostic aids in orthodontics /certified fixed orthodontic courses by Indian dental academy

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Diagnostic aids in orthodontics /certified fixed orthodontic courses by Indian dental academy

Similar to Diagnostic aids in orthodontics /certified fixed orthodontic courses by Indian dental academy (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Diagnostic aids in orthodontics /certified fixed orthodontic courses by Indian dental academy