Recent Advances in Radiographic Technique in Orthodontics

Recent Advances in
Radiographic Technique
in Orthodontics
www.indiandentalacademy.com

Introduction
• In this seminar I would like to highlight on
contemporary imaging techniques & innovations in
imaging that in the future, are likely to greatly
improve the depiction of craniofacial structures for
use in diagnosis & treatment planning.It would be
appropriate to first discuss the evolution of cranio
facial imaging in orthodontics & review the
limitations of current methods, including the two
dimensional representation of three dimensional
anatomy

Historical Perspective
• In 1895 Roentgen discovered X-ray
• In 1931 Broadbent introduced
roentgenographic cephalometry
• Cephalometrics was introduced in 1922 by
Pacini &Carera.Others who contributed
were Mac Gowen in 1923, Comet in 1927
&Reisner in 1929

Historical Perspective
• Walker in 1972, Savara in 1972&Ricketts
Et Al in 1972 made an attempt in the
development of dentofacial imaging in 3-D
individually & together with & without
computerization

The X-ray machine
• Apparatus consists of
1.Cathode-which serves as a source of
electrons
2.Anode-at which the beam of high speed
electrons are targeted
both of these are encased with in an evacuated
glass envelope or tube. X-ray are produced
when electrons strike the target

contd
• In order for the x-ray tube to function,an
electrical power supply is necessary to
establish high potentials across the tube for
accelerating the electrons to very high
speeds

X-ray film
• Composed of two principal components, the
emulsion & the base
• Emulsion is sensitive to x-rays & visible
light and records the radiographic image
• Base is the supporting material onto which
the emulsion is coated.

contd
• The principal components of emulsion are
the silver halide crystals,which are
photosensitive,and a gelatin matrix that
supports these crystals.An additional layer
of gelatin act as a super coating to film
emulsion which helps in protecting the film
from damage by scratching or
contamination

FILM BASE
• Their function is to support the light
sensitive silver halide grains & gelatin
emulsion. They should have proper amount
of flexibility to allow ease in handling the
film. It should be evenly translucent
• Dental x-ray film base is composed of poly
ethylene terephthalate & is about 0.2mm
thick

contd
• To achieve good adhesion between the
emulsion & the film base a thin layer of
adhesive material is added to the base
before application of the emulsion.

Goals & principles of
Craniofacial Imaging
• Assessment of pathology & any deviations
from normal.
• Comparison of out comes of different
treatment methods at different maturational
stages.
• Assessment of preceeding growth or
estimation of the direction or magnitude of
expected growth.

contd
• Distinguishing the effects of treatment from
the expected effects of un altered growth .
The ideal imaging modality maximizes the
desired information & minimises the
physiological risk & expense to the patient.

Xero Radiography
• It is a specialised technique which does not
make use of the wet processing technique of
the image receptor after being exposed to
X-rays
• Image formation is achieved by photo
electro static process & not by photo
chemical process as in conventional radio
graphy

contd
• Found its application in the medical field in
the early part of 1950’s
• uses materials such as selenium that are
photoconductors &conduct electric current
when they interact with electro magnetic
radiation such as light or x-rays

Advantages
• No necessity of handling wet film
• no requirement of dark room, processing
solution & replenisher
• dry & permanent image formed& cost
effective
• the image has a broader recording latitude
• better resolution
• image has less granularity.www.indiandentalacademy.com

contd
• Less radiation exposure
• image have good detail &edge enhancement
• visible image of air, fat,water,cartilage &
bone can be seen

PANORAMIC RADIOGRAPHY
• It is a specialized extra oral radiographic
technique used to examine the upper &
lower jaws in a single film.
• Also called as rotational panoramic
radiography or Pantomography.
• In this technique, the film & the tube head
rotate around the patient,who remains
stationery & produce a series of individual
images successively in a single filmwww.indiandentalacademy.com

Purpose & uses
• For visualizing maxilla &mandible in one
film
• patient education
• to evaluate impacted teeth & multiple
unerupted super numerary teeth
• detect any pathology involving jaws
• to determine the extent of a large lesion
• to evaluate traumatic injurieswww.indiandentalacademy.com

contd
• X’mination of patient with limited mouth
opening
• to identify diseases of the TMJ

Disadvantages
• Images are not sharp
• cannot be used in the diagnosis of caries
• can not be used to evaluate bone loss due to
periodontal disease
• super imposition especially in the premolar
region
• structures in the anterior region not well
defined

contd
• Structures outside the image layer cannot be
visualised

CEPHALOMETERY
• Cephalograms have been widely used, both
as a clinical tool & as a research technique
for the study of cranio facial growth &
orthodontic treatment
• when a 3-D object is represented in 2-D,
structures are displaced vertically &
horizontally in proportion to their distance
from the film or recording plane

contd
• Ceph analysis are based on the assumption
of a perfect super imposition of the RT&
LT sides about the mid sagittal plane, but
this is observed rare because of the facial
asymmetry
• Radiographic projection error causes size
magnification & distortion,errors in patient
positioning,& projective distortion inherent
to the filmpatientfocus geometricwww.indiandentalacademy.com

contd
• Manual data collection & processing was
low in accuracy & precision
• Large errors are associated with ambiguity
in locating anatomical land marks due to the
lack of well defined out lines hard edges &
shadows,as well as variation in patient
position

contd
• Hatcher in 1999 categorized sources of
error related to traditional cephalometrics as
those due to internal & external orientation
& those related to geometry & association
error
• Internal orientation error refers to the 3-D
relationship of the patient relative to the
central X-ray beam

contd
• External- This refers to the 3-D spatial
relationship or alignment of the imaging
device, patient stabilizing device & the
image recording device
• Geometric- this primarily refers to the
differential magnification created by
projection distance between the imaging
device the image recording device& a 3-d
object www.indiandentalacademy.com

contd
• Association error- This refers to the
difficulty in identifying a point in two or
more projections acquired from different
points of view

contd
• When computers are used they may
introduce errors related to pixel size, loss of
color & contrast information & incomplete
caliberation
• In 1931 Broadbent introduced the
roentgenographic cephalogram
• efforts at minimizing errors & achieving
accurate 3-D representation of the cranio
facial complex have included computerwww.indiandentalacademy.com

Conventional craniofacial
imaging modalities
• Classified as - techniques providing
information on Hard tissue & those on soft
tissue. In some instances, information on
both hard &soft tissues may be obtained
together to varying degrees

Hard tissue imaging techniques
• Lateral & Postero anterior cephalograms
• Panoramic radiography
• Limited or full mouth series (FMX)
consists of bite wings & periapical
projections.this should be selected on a case
by case basis, since the potential risks due
to ionizing radiations are real

Indication
• To assess the periodontal status and root
morphology & length in adult patients
From a strict orthodontic perspective
these images provide several benefits
including the ability to assess overall dental
& periodontal health, root length shape &
form ;presence of periodontal ligament
space to help rule out the possiblity of
ankylosis;positions of impacted or eruptingwww.indiandentalacademy.com

Hand wrist radiographs
• They aid in providing an estimate of
remaining growth, since a positive co
relation between skeletal growth assessed
by this method & facial growth has been
reported. It should be used in conjunction
with other indicators of overall body
growth& development.

Tomography
• General term used for technique that
provides an image of alayer of tissue.The
versatality of this technique makes
tomography highly desirable for accurate
imaging of maxillofacial structures,
including the TMJ & for cross sectional
imaging of the maxilla &mandible.Modern
complex- motion tomographic units can be
optimized to image any selected region of
the facial skeleton

TMJ & SOFT TISSUE
IMAGING
• Methods may be either 2-D or 3-D
• 2-D imaging includes conventional
radiology
(transcranial,transpharyngeal,transmaxillary
submental-vertex)anthrography&fluroscopy
• 3-D images include MRI, CT &most recent
is stereometry

Corrected tomography of TMJ
• Because of its ability to image the TMJ
quickly &relatively inexpensively it is the
most widely used technique for examining
the hard tissues of jaw point
• Axially corrected TMJ tomography refers to
the allignment of the tomographic beam
with the mediolateral long axis of the
condyle to produce image layers that are
parellel or perpendicular to the mediolateralwww.indiandentalacademy.com

contd
• The value of this technique is limited a
priori by its two-dimensional nature, as well
as by its inability to show the disc

Computed tomography
• It uses a computer to aid in generating the
image, & in allowing multiple CT slices to
be stacked to give an idea of the 3-D form
• CT is inefficient at producing suitable soft
tissue contrast

MRI
• It is preferred when information regarding
the articular disc, or the presence of
adhesions, perforations or joint effusion is
desired
• produces image with out ionizing radiation
• expensive
• para magnetic contrasting material is
required in distinguishing between soft
tissues of similar signal intensitywww.indiandentalacademy.com

Arthrography
• It relies on radiographic image acquisition
following intra-articular administration of
an iodinated contrast agent,which is placed
under fluoroscopic guidance
• it helps in understanding the disk position
• it has an advantage over MRI in identifying
the perforations between the superior &
inferior joint compartments & adhesions

disadvantages
• Increased patient risks related to radiation
dosage
• per cutaneous injection into the TMJ
• potential for allergic reaction

Imaging & safety patterns
• Rare earth screensfilm systemsrare earth
filtrationthe use of grids ,and the use of pre
patient filtered soft tissue enhancement
methods
• the radiation dose of panoramic films = to a
single periapical or bite wing radiograph,
these imaging methods may function in a
screening capacity prior to deciding on the
need for additional radiographwww.indiandentalacademy.com

Contemporary & evolving
imaging technique
• Images are points of information that can be
produced either by the conventional analog
process or by a more contemporary digital
one.Intrest in digital imaging has grown for
number of different reasons
• In terms of necessity ,use of digital imaging
allows the operator to manipulate data on a
computer

contd
• In terms of biology, this technique reduce
patient radiation exposure by 30 to 98%
• In terms of practicality, the elimination of
hard copy X-ray film may decrease storage
needs & enable teleradiology

DIGITAL CEPH
• Considering time,tediousness&systamatic
error associated with manual cephalometric
data collection &processing automated
Land mark identification & computerised
cephalometric analysis have also recieved
major attention. Human error associated
with land mark location is reduced.It
requires a scanner for image acquisition

Advantages
• It allows for multiple cephalometric
analyses to be performed simultaneously
• It also facilitate the performance of repeated
digitization of landmarks
• since it is in digital form , it can be
integrated with other digital information,
such as intra oral & extra oral digital
photographs & tomographs

Developments in craniofacial
imaging
• The future of craniofacial imaging lies in
the generation of efficient ,inexpensive &
detailed 3-D images for diagnosis &
treatment planning .CT’s ,micro CT’s
,tuned aperature CT’s & MR spectroscopy
aim to achieve many of these objectives

Computed tomography
• Although CT scans are too x’pensive &
have too high a radiation dose, they are
useful in
• treatment of cranio facial deformities
• the outcome of surgical procedures may be
visualised using sophisticated CT
techniques

Micro computed tomography
• It is principally the same as CT except that
the reconstructed cross sections are
confined to a much smaller area.The future
of micro CT lies in its ability to sample data
over a much smaller volume than full body ,
significantly reducing the radiation
exposure.It is used to evaluate
osteoblasticosteoclastic alveolar
remodelling &root resorptionwww.indiandentalacademy.com

TACT
• The national institute of dental research
elected in 1990 to support the development
of a system for generating 3D images from
a machine consisting of a multitube X-ray
and an X-ray CCD screen
• TACT system is able to convert multiple
2D images created from multiple arbitrary
projection source into a 3D image

MR spectroscopy
• MRI works by obtaining a resonance signal
from the hydrogen nucleus, & there fore is
essentially an imaging of water in the
tissue.MR spectroscopy works in a similar
manner, but allows the imaging of any
molecule or compound in the tissue.It is
useful in the study of skeletal muscle
physiology, tumors &healing of grafts

Structured light
• Structured light scanning enables the
topology of the face to be digitized simply
& with out ionizing radiation. The result is
a 3-D shell of a patients face,viewable on a
computer monitor
• the goal of this is to merge the facial shell &
underlying X-ray data from other sources to
complete the 3D structure for diagnosis
&treatment planningwww.indiandentalacademy.com

Stereo photogrammetry
• It involves photographing a 3-d object from
two different coplanar views in order to
derive a 3D reconstruction of the images.
• Modern stereo photogrammetry can be
applied to solve accurate 3D skull mapping.
• Using a bundle ,adjustment method,both the
geometric calibration and 3D mapping
functions can be elegant and accurate .

Laser-Doppler flowmetry
• A 2mw Helium neon laser with in the
flowmeter produced light with a wavelength
of 632.8nm was sent along a flexible fiber-
optic conductor inside the probe to the
recording site.Light that contacted moving
RBC was doppler shifted and some of this
back scattered light was returned to the
flowmeter .The flowmeter then processed
the amount of doppler shifted light that waswww.indiandentalacademy.com

Contd.
returned and produced an output signal that
was measured in volts .

Assessment of Skeletal
Maturation
• It can be assessed using
• 1)Hand-wrist X-rays
• 2)Frontal sinus
• 3)Canine calcification
• 4)Cervical vertebrae

Conclusion
• The advances in imaging will substantially
enhance our ability to identify conditions
that are not detectable with currently
available imaging techniques, and will help
improve the accuracy & reliability of
diagnosis & treatment

Recent Advances in Radiographic Technique in Orthodontics

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