Cephalometric landmarks

RADIOLOGY IN ORTHODONTICSRADIOLOGY IN ORTHODONTICS
www.indiandentalacademy.comwww.indiandentalacademy.com

 IntroductionIntroduction
 Radiation physicsRadiation physics
 Radiation biologyRadiation biology
 Radiographic techniquesRadiographic techniques
 Specialized radiographic techniquesSpecialized radiographic techniques
 Diagnostic imaging of TMJDiagnostic imaging of TMJ
 Maxillary canine projectionsMaxillary canine projections
 ConclusionConclusion www.indiandentalacademy.comwww.indiandentalacademy.com

INTRODUINTRODUCTIONCTION
The use of X Rays in an integral part of clinicalThe use of X Rays in an integral part of clinical
dentistry with some form of radiographic examinationdentistry with some form of radiographic examination
necessary on the majority of patients. As a result,necessary on the majority of patients. As a result,
radiographs are often referred to as the clinician’s mainradiographs are often referred to as the clinician’s main
DIAGNOSTIC AID.DIAGNOSTIC AID.

RADIATION PHYSICS

XRAYXRAY
 Discovery by Roentgen in 1895.Discovery by Roentgen in 1895.
 X Rays are form of high energy electromagnetic radiationX Rays are form of high energy electromagnetic radiation
& part of electromagnetic spectrum, which also includes low& part of electromagnetic spectrum, which also includes low
energy radio waves, television & visible light.energy radio waves, television & visible light.
PRODUCTION OF X RAYSPRODUCTION OF X RAYS
X Rays are produced when energetic (high speed) electrons
bombard a target material & are brought suddenly in to rest. This
happens inside a small evacuated glass envelope called X Ray
tube.

X RAY MACHINE
 l. X Ray tube
 2. Power supply
I.X Ray tube
 1) Cathode 2) Anode
 When electrons from the cathode
strike the target in the anode,
they produce X Rays.
 Cathode -- Consists of Filament (
electron production)
Focusing Cup. (Mb)
 Anode -- Consists of tungsten
target embedded in copper stem.
(electron’s kinetic energy is
converted in to X Ray Photon)

II. Power SupplyII. Power Supply
FunctionsFunctions
1. Provide low – voltage current to heat the X Ray tube1. Provide low – voltage current to heat the X Ray tube
Filament by use of step down transformer.Filament by use of step down transformer.
2. Generate a high potential difference between the anode2. Generate a high potential difference between the anode
and cathode by use of high voltage transformer.and cathode by use of high voltage transformer.

PRODUCTION OF X RAYSPRODUCTION OF X RAYS
II.. BREMSSTRAHLUNG RADIATIONBREMSSTRAHLUNG RADIATION..
 IfIf High speed electrons hits the nucleiHigh speed electrons hits the nuclei
of a target atom, all its kinetic energy isof a target atom, all its kinetic energy is
transformed in to single X Ray Photon.transformed in to single X Ray Photon.
 The energy of the resultant photon isThe energy of the resultant photon is
numerically equal to the energy of thenumerically equal to the energy of the
electron.electron.
II.II. CHARACTERISTIC RADIATONCHARACTERISTIC RADIATON..
 It occurs when an electron from aIt occurs when an electron from a
filament displaces an electron from afilament displaces an electron from a
shell of a tungsten target atom. Whenshell of a tungsten target atom. When
the displaced electron is replaced bythe displaced electron is replaced by
the outer-shell electron, a PHOTON isthe outer-shell electron, a PHOTON is
emitted with an energy equivalent toemitted with an energy equivalent to
the difference in the two orbital bindingthe difference in the two orbital binding
energies.energies.

PROPERTIES OF X RAYSPROPERTIES OF X RAYS
 They are wave packets of energy of
electromagnetic radiation that originate at the
atomic level.
 Each wave packet is equivalent to a quantum of
energy and is called as PHOTON.
 Velocity is 3 x 10 8m/s.
 Shorter wavelength X - Ray posses Increase
energy and penetrate greater distance.

FACTORS CONTROLLING X RAY BEAM.FACTORS CONTROLLING X RAY BEAM.
 i) Exposure timei) Exposure time
ET =ET = NoNo of photons generatedof photons generated
(energy is unchanged) only quantity control.(energy is unchanged) only quantity control.
 ii) Tube currentii) Tube current
TC = No of photonTC = No of photon..
 iii) Tube voltageiii) Tube voltage
TV =TV = NO of photonsNO of photons..
Mean energyMean energy
Maximal energy.Maximal energy.
Bramsstrahlung photons.Bramsstrahlung photons.
Quality control.Quality control.

FILTRATIONFILTRATION
To reduce the pTo reduce the patient dose, the less penetrating photonsatient dose, the less penetrating photons
should be removed. This can be accomplished by placing ashould be removed. This can be accomplished by placing a
Aluminium filter in the path of the beam.Aluminium filter in the path of the beam.
COLLIMATIONCOLLIMATION
It is a Metallic barrier with an aperture in the middle.It is a Metallic barrier with an aperture in the middle.
Used to reduce the size of the X Ray beam, and thereforeUsed to reduce the size of the X Ray beam, and therefore
the volume of irradiated tissue with in the patient.the volume of irradiated tissue with in the patient.
Types 1. RoundTypes 1. Round
2.rectanqular2.rectanqular
3.circle3.circle

DDOSIMETRYOSIMETRY
 Determining the quantityDetermining the quantity of radiation exposure (or) dose.of radiation exposure (or) dose.
UNITS OF MEASUREMENTUNITS OF MEASUREMENT:-:-
QuantityQuantity SI UnitSI Unit Traditional UnitTraditional Unit
(a) Exposure(a) Exposure C/KgC/Kg RoentgenRoentgen
(b) Absorbed Dose Gray(b) Absorbed Dose Gray RadRad
(c) Equivalent (or)(c) Equivalent (or)
effective doseeffective dose SievertSievert RemRem
(d) Radioactivity(d) Radioactivity Becquerel (Bg)Becquerel (Bg) CurieCurie

IMAGE RECEPTORS (FILMIMAGE RECEPTORS (FILM))
Composition:-Composition:-
(i) Emulsion(i) Emulsion (ii) Ba(ii) Basese
EmulsionEmulsion - It is sensitive to- It is sensitive to
X Rays & visible light,X Rays & visible light,
records the radiographicrecords the radiographic
Image.Image.
BaseBase
- it is a plastic supporting- it is a plastic supporting
material on to which thematerial on to which the
emulsion is coated.emulsion is coated.
TypesTypes
 direct actions or nondirect actions or non
screen film ex- IOPAscreen film ex- IOPA
 indirect actions or screenindirect actions or screen
film ex- extra oral film (film ex- extra oral film (
it is used in combinationit is used in combination
with intensifying screen)with intensifying screen)

INTENSIFYING SCREENINTENSIFYING SCREEN
 It transfers X-Ray energy into visible light and this in turnIt transfers X-Ray energy into visible light and this in turn
exposes the screen films. So less radiation exposure andexposes the screen films. So less radiation exposure and
less radiation time is required.less radiation time is required.
BaseBase
These are made up of polyester plastic measures .These are made up of polyester plastic measures .
25mmthickness.25mmthickness.
It provides mechanical support for the screen.It provides mechanical support for the screen.
Reflecting layerReflecting layer
It is a white layer of titaniumIt is a white layer of titanium
dioxide coated on the base lies beneathdioxide coated on the base lies beneath
the phosphor layer. It reflects any lightthe phosphor layer. It reflects any light
emitted from the phosphor layer back toemitted from the phosphor layer back to
the X-Ray film.the X-Ray film.
Phosphor layerPhosphor layer
It consists of light sensitiveIt consists of light sensitive
phosphor crystals suspended in aphosphor crystals suspended in a
plastic material. When phosphors areplastic material. When phosphors are
struck by photons, they fluorescence i.estruck by photons, they fluorescence i.e
they emit visible light photons thatthey emit visible light photons that
exposes X-ray film.exposes X-ray film.

Most common phosphor used areMost common phosphor used are
 Calcium tungstate that fluorescence in blue portion ofCalcium tungstate that fluorescence in blue portion of
spectrum phosphor used by rare earth intensifying screen.spectrum phosphor used by rare earth intensifying screen.
 Terbium activated gadolinium oxysulfide.Terbium activated gadolinium oxysulfide.
 Thulium activated lanthanum oxybromide that fluorescenceThulium activated lanthanum oxybromide that fluorescence
in green position of spectrum.in green position of spectrum.
AdvantageAdvantage
 They respond to a shorter exposure to X Rays, enabling aThey respond to a shorter exposure to X Rays, enabling a
lower dose of radiation to be given to the pt.lower dose of radiation to be given to the pt.
DisadvantageDisadvantage
 Inferior image qualityInferior image quality

RADIOGRAPHIC IMAGERADIOGRAPHIC IMAGE
CHARACTERSTICSCHARACTERSTICS
(i)(i) Radiographic DensityRadiographic Density -- ∞∞ Exposure time (x)Exposure time (x)
∞∞ Subject ThicknessSubject Thickness
∞∞ Subject DensitySubject Density
(ii)(ii) ContrastContrast -- Subject contrast (Subject’sSubject contrast (Subject’s
thickness, density andthickness, density and
atomic no)atomic no)
Film contrast (Intensity ofFilm contrast (Intensity of
the remnant beam)the remnant beam)
Scattered radiation.Scattered radiation.
(iii)(iii) Radiographic SpeedRadiographic Speed
Fast film requiresFast film requires -- exposureexposure
SlowSlow -- exposureexposure
(iv)(iv) Image QualityImage Quality -- by using Grid.by using Grid.
(Reduces the amount of(Reduces the amount of
scattered radiation).scattered radiation).

RELATIVE RADIATION EXPLOSURE

RADIATION BIOLOGY

Radiation effects at the tissue andRadiation effects at the tissue and
organ levelorgan level
 The radio sensitivity of a tissue or organ isThe radio sensitivity of a tissue or organ is
measured by its response to radiation.measured by its response to radiation.
Short term effectsShort term effects
 Of radiation on a tissue is determined primarilyOf radiation on a tissue is determined primarily
by the sensitivity of its parenchymal cells. Cellsby the sensitivity of its parenchymal cells. Cells
are lost primarily by mitosis linked death.are lost primarily by mitosis linked death.
 Extent of cell loss depends on – damage to theExtent of cell loss depends on – damage to the
stem cell pools & proliferative rate of cellstem cell pools & proliferative rate of cell
population.population.
Long term effectsLong term effects
 The long term deterministic effects of radiation onThe long term deterministic effects of radiation on
tissues and organs depend primarily on thetissues and organs depend primarily on the
extent of damage to the fine vasculature.extent of damage to the fine vasculature.

Radiation effects of oral tissuesRadiation effects of oral tissues
Oral mucous membraneOral mucous membrane
• mucositismucositis
• secondary candida albicans infectionsecondary candida albicans infection
• long term – atrophic changes due to progressivelong term – atrophic changes due to progressive
obliteration of fine vasculature and fibrosisobliteration of fine vasculature and fibrosis
Taste budsTaste buds Extensive degeneration.Extensive degeneration.
Salivary glandsSalivary glands
• XerostomiaXerostomia
• Ph to 5.5↓Ph to 5.5↓
• Progressive fibrosis, adiposis, loss of fine vasculatureProgressive fibrosis, adiposis, loss of fine vasculature
and parenchymal degenerationand parenchymal degeneration
TeethTeeth
• radiation cariesradiation caries..
BoneBone
• Normal marrow may be replaced with fatty marrow andNormal marrow may be replaced with fatty marrow and
fibrous connective tissuefibrous connective tissue
• OsteoradionecrosisOsteoradionecrosis
Late somatic effectsLate somatic effects
• Carcinogenesis and leukemiaCarcinogenesis and leukemia

ALARA
The most recent recommendations involving the establishment
of permissible doses and dose limits to occupational and
nonoccupational groups can be summarized in the principle of
ALARA (As low as reasonably achievable).
This means that every available method for reducing exposure
to ionizing radiation will be implemented to minimize
potential risks and adverse consequences

Protective measures that aim to minimize the radiation exposure to
the patient are:
•Utilization a high sped film and intensifying screens to reduce
the dose of radiation and the exposure time.
•Filtration of secondary radiation or scatter radiation produced
by low energy x-ray photons by an aluminum filter.
•Collimation by a diaphragm made of lead in order to achieve
optimal beam size

•Proper exposure technique and processing in order to avoid
unnecessary repetition of the procedure.
•The patient’s wearing a lead apron in order to absorb scatter
radiation.
•In order to avoid scatter radiation the operator must stand at least 6
feet behind the tube head or should stand behind a lead protective
barrier while making the x-ray exposure.

TYPES OF RADIOGRAPIC TECHNIQUESTYPES OF RADIOGRAPIC TECHNIQUES
I Intra oralI Intra oral -- IOPA, Bitewing, Occlusal.IOPA, Bitewing, Occlusal.
II Extra OralII Extra Oral -- Oblique lateral, variousOblique lateral, various
skull projections OPG.skull projections OPG.
INTRA ORAL PERIAPICAL RADIOGRAPHINTRA ORAL PERIAPICAL RADIOGRAPH:-:-
It shows 2 to 4 teeth & provides detailed informationIt shows 2 to 4 teeth & provides detailed information
about the teeth and surrounding alveolar bone.about the teeth and surrounding alveolar bone.
Indications:-Indications:-
 Detection of apical Infection / Inflammation.Detection of apical Infection / Inflammation.
 Periodontal status detection.Periodontal status detection.
 Assessment of pressure & position of unerupted teeth.Assessment of pressure & position of unerupted teeth.
 Evaluation of implants post operatively.Evaluation of implants post operatively.
Techniques:-Techniques:-
 Paralleling techParalleling tech
 Bisected angle techBisected angle techwww.indiandentalacademy.comwww.indiandentalacademy.com

PARALLELING TECHPARALLELING TECH
( Right angle intra oral tech )( Right angle intra oral tech )
(or)(or)
(Long cone tech.)(Long cone tech.)
Procedure:-Procedure:-
- X Ray film in supported to- X Ray film in supported to
the long axis of the teeththe long axis of the teeth
by film holder & the centralby film holder & the central
beam in directed at rightbeam in directed at right
angle to the teeth & theangle to the teeth & the
filmfilm
–– To further reduceTo further reduce
geometric distortion X Raygeometric distortion X Ray
source be located relativelysource be located relatively
distant from the teeth.distant from the teeth.

BISECTING ANGLE TECHBISECTING ANGLE TECH
• Based on the simple geometricBased on the simple geometric
theorem (i.e.) (ieszynski’s ruletheorem (i.e.) (ieszynski’s rule
of isometry), which states the 2of isometry), which states the 2
angles are equal when theyangles are equal when they
share one complete side & haveshare one complete side & have
2 equal angles.2 equal angles.
• The plane of the film & long axis of the teeth form anThe plane of the film & long axis of the teeth form an
angle with its apex at the point where the film isangle with its apex at the point where the film is
inin contact with the teeth. When this angle is bisected by ancontact with the teeth. When this angle is bisected by an
imaginary line or plane, 2 congruent angles with aimaginary line or plane, 2 congruent angles with a
common side (Imaginary bisector) formed. central ray iscommon side (Imaginary bisector) formed. central ray is
directed at a right angle to the plane that bisects thedirected at a right angle to the plane that bisects the angleangle
between the long axis at the tooth & the film.between the long axis at the tooth & the film.

OBJECT LOCALIZATIONOBJECT LOCALIZATION
TUBE SHIFT TECHNIQUE (BuccalTUBE SHIFT TECHNIQUE (Buccal
object rule, Clark' rule)object rule, Clark' rule)
 The relative positions of radiographicThe relative positions of radiographic
images of two separate objects changeimages of two separate objects change
when the projection angle at which thewhen the projection angle at which the
images were is changed.images were is changed.
 If the object in question appears toIf the object in question appears to
move in the same direction with respectmove in the same direction with respect
to the reference structures as does theto the reference structures as does the
X-ray tube, it is on the lingual aspect ofX-ray tube, it is on the lingual aspect of
the reference object.the reference object.
 If it appears to move in the oppositeIf it appears to move in the opposite
direction of the X-ray tube, it is on thedirection of the X-ray tube, it is on the
buccal aspect. If it does not move withbuccal aspect. If it does not move with
respect to the reference object ,it lies atrespect to the reference object ,it lies at
the same depth (in the same verticalthe same depth (in the same vertical
plane) as the reference objectplane) as the reference object

RIGHT ANGLE TECHNIQUERIGHT ANGLE TECHNIQUE
 Two projections taken atTwo projections taken at
right angles to one anotherright angles to one another
localize an object. Inlocalize an object. In
clinical practice theclinical practice the
position of an object onposition of an object on
each radiograph is notedeach radiograph is noted
relative to the anatomicalrelative to the anatomical
land marks. This allows anland marks. This allows an
observer to determine theobserver to determine the
position of the object or anposition of the object or an
area of interest.area of interest.

Stanley A. Jacobs et al (AJO 2000).Stanley A. Jacobs et al (AJO 2000).
A rotational panoramic radiograph with an ant occlusalA rotational panoramic radiograph with an ant occlusal
radiograph is a preferred combination of radiographs toradiograph is a preferred combination of radiographs to
localize unerupted mandibular anterior teeth. Thislocalize unerupted mandibular anterior teeth. This
combination uses a tube shift in the vertical plane. Thecombination uses a tube shift in the vertical plane. The
rotational panoramic radiograph is taken at an effectiverotational panoramic radiograph is taken at an effective
angle of +7°C to the occlusal plane & anterior occlusalangle of +7°C to the occlusal plane & anterior occlusal
radiograph is taken at -55°C.radiograph is taken at -55°C.
Conor Armstrong (EJO - 2003).Conor Armstrong (EJO - 2003).
States that localization of ectopic maxillary caninesStates that localization of ectopic maxillary canines
was significantly more successful with horizontal parallaxwas significantly more successful with horizontal parallax
than with vertical parallax. But both radiographicthan with vertical parallax. But both radiographic
techniques were poor at localizing buccal EMC (success ratetechniques were poor at localizing buccal EMC (success rate
is only 63%).is only 63%).

BITE WING RADIOGRAPHBITE WING RADIOGRAPH
Film in designed to show the crowns of the premolar &Film in designed to show the crowns of the premolar &
molar teeth on one side of the jaw.molar teeth on one side of the jaw.
Indications:-Indications:-
 To detect proximal Dental Caries.To detect proximal Dental Caries.
 Monitoring the progression of Dental Caries.Monitoring the progression of Dental Caries.
 Assessment of existing restoration.Assessment of existing restoration.
 Assessment periodontal status.Assessment periodontal status.
Technique:Technique:--
 Film in placed between tongue & teeth, close to theFilm in placed between tongue & teeth, close to the
lingual surface of the teeth & parallel to the long axis.lingual surface of the teeth & parallel to the long axis.
Film tab should be centered in occlusal line.Film tab should be centered in occlusal line.
 X Ray is projected to the center of the film throughX Ray is projected to the center of the film through
contact areas (angle 5 degree)contact areas (angle 5 degree)

OCCLUSAL RADIOGRAPHYOCCLUSAL RADIOGRAPHY
(a) Topographical(a) Topographical - Ant- Ant
Maxilla & dentition, antMaxilla & dentition, ant
nasal fossa.nasal fossa.
(b) Cross Sectional(b) Cross Sectional - Palate,- Palate,
Zygomatic Process ofZygomatic Process of
Maxilla, nasolacrimal CanalMaxilla, nasolacrimal Canal
Nasal Septum, 2nd MolarNasal Septum, 2nd Molar
to 2nd Molar.to 2nd Molar.
( c) Lateral Topographical( c) Lateral Topographical
• Half of the ridge ofHalf of the ridge of
Maxilla,Maxilla,
Inferio Lateral aspect ofInferio Lateral aspect of
the antrum, tuberosity,the antrum, tuberosity,
teeth from lateralteeth from lateral
incisor to molar.incisor to molar.
Maxillary occlusalMaxillary occlusal

(a ) Cross Sectional(a ) Cross Sectional
Lingual & Buccal Plates of the jaw bone 2Lingual & Buccal Plates of the jaw bone 2ndnd
molar to 2molar to 2ndnd
molar.molar.
(b) Lateral cross section(b) Lateral cross section
Soft palate, half of the floor of the mouth, buccal &Soft palate, half of the floor of the mouth, buccal &
lingual cortical plate (Lateral incisor to 3rd molar).lingual cortical plate (Lateral incisor to 3rd molar).
UsesUses:-:-
 To Precisely locate roots, supernumery unerupted &To Precisely locate roots, supernumery unerupted &
Impacted teeth (canine to 3rd molar)Impacted teeth (canine to 3rd molar)
 To aid in examining – pt with trismus who can open theTo aid in examining – pt with trismus who can open the
mouth only a few mm.mouth only a few mm.
MANDIBULAR OCCLUSALMANDIBULAR OCCLUSAL

EXTRA ORAL RADIOGRAPHICEXTRA ORAL RADIOGRAPHIC
TECHNIQUESTECHNIQUES
• Lateral cephalometric projection ( sagital (or) Median)Lateral cephalometric projection ( sagital (or) Median)
• submento Vertex ( Transverse (or) horizontal)submento Vertex ( Transverse (or) horizontal)
• Water’s projectionWater’s projection
• Postero anterior ( Frontal view)Postero anterior ( Frontal view)
I.I. SUBMENTO VERTEXSUBMENTO VERTEX:-:-
It reveals the position and orientation of theIt reveals the position and orientation of the
condyle, curvature of the mandible.condyle, curvature of the mandible.
II.II. WATERS PROJECTIONWATERS PROJECTION:-:-
Used to evaluate orbit, nasal cavity andUsed to evaluate orbit, nasal cavity and
maxillary sinus.maxillary sinus.

POSTERO ANTERIOR VIEWPOSTERO ANTERIOR VIEW
The X ray passes in a posterior anterior direction through theThe X ray passes in a posterior anterior direction through the
skull.skull.
A cassette is positioned vertically in a holding device. A gridA cassette is positioned vertically in a holding device. A grid
is usedis used
Head is centered in front of the cassette with the canthoHead is centered in front of the cassette with the cantho
meatal line.meatal line.
UsesUses
 To detect developmental abnormalities like facialTo detect developmental abnormalities like facial
asymmetries.asymmetries.
 Used to examine the skull for presence of disease, trauma,Used to examine the skull for presence of disease, trauma,
developmental abnormalities.developmental abnormalities.
 Used to detect progressive change in the mediolateralUsed to detect progressive change in the mediolateral
dimensions of the skull.dimensions of the skull.
 It offers good visualization of facial structures includingIt offers good visualization of facial structures including
frontal, ethmoidal sinus, nasal fossa and orbits.frontal, ethmoidal sinus, nasal fossa and orbits.www.indiandentalacademy.comwww.indiandentalacademy.com

POSTERO ANTERIOR VIEWPOSTERO ANTERIOR VIEW

LATERAL CEPHALOMETRYLATERAL CEPHALOMETRY
““CephalometryCephalometry” the term may mean a simple consideration of” the term may mean a simple consideration of
anatomic part of the skull in the head plate or the treatment ofanatomic part of the skull in the head plate or the treatment of
measurements by the use of analytic geometry.measurements by the use of analytic geometry.
History:-History:-
 1922 – Pacini Introduced a method for standardized head1922 – Pacini Introduced a method for standardized head
radiography.radiography.
 1931 – Broad Bent in the US1931 – Broad Bent in the US
Hofrath in Germany-introduced modern cephalometry.Hofrath in Germany-introduced modern cephalometry.
 Pacini –Pacini – Large fixed distance from the X Ray source to theLarge fixed distance from the X Ray source to the
cassette. The head of the subject is placed adjacent to a standcassette. The head of the subject is placed adjacent to a stand
holding the cassette and war immobilized with a gaugeholding the cassette and war immobilized with a gauge
bandage wrapped around both the face and the cassette, afterbandage wrapped around both the face and the cassette, after
the pt’s midsagittal plane was carefully oriented parallel to thethe pt’s midsagittal plane was carefully oriented parallel to the
cassette.cassette.
 Broad BentBroad Bent;- Involves a constant focal spot to object distance;- Involves a constant focal spot to object distance
(5 feet) &constant object to film distance (9cm)(5 feet) &constant object to film distance (9cm)
 Lucien de costerLucien de coster – was the first to publish an analyses based– was the first to publish an analyses based
on proportional relationships in the face conforming to theon proportional relationships in the face conforming to the
principles used in antiquity.principles used in antiquity.

RADIOGRAPHIC CEPHALOMETRICRADIOGRAPHIC CEPHALOMETRIC
TECHNIQUETECHNIQUE
Simplest procedure toSimplest procedure to
obtain head radiographs inobtain head radiographs in
natural head position is tonatural head position is to
instruct the patients to sitinstruct the patients to sit
upright and look straightupright and look straight
ahead to a point at eyeahead to a point at eye
level on the wall in front oflevel on the wall in front of
them.them.
Patient is positioned withinPatient is positioned within
the cephalostat usingthe cephalostat using
adjustable bilateral ear rodsadjustable bilateral ear rods
placed within each auditoryplaced within each auditory
meatus, usually while themeatus, usually while the
patient is in the standingpatient is in the standing
position. The midsagital planeposition. The midsagital plane
of the patient is vertical andof the patient is vertical and
perpendicular to the X Rayperpendicular to the X Ray
beam. It is also parallel to thebeam. It is also parallel to the
film plane which in turnfilm plane which in turn

OREINTATION IN NATURAL HEADOREINTATION IN NATURAL HEAD
POSITIONPOSITION
Orientation of pts in natural head positionOrientation of pts in natural head position
will result in only a small range of error. Suchwill result in only a small range of error. Such
differences have only minor effect on thedifferences have only minor effect on the
interpretation of facial morphologic features &interpretation of facial morphologic features &
facial disharmonyfacial disharmony

LATERAL CEPHALOGREMLATERAL CEPHALOGREM

CLINICAL USESCLINICAL USES
(i) GROSS INSPECTION(i) GROSS INSPECTION
To observe gross anatomic relations of skeletal & soft tissuesTo observe gross anatomic relations of skeletal & soft tissues
in the lateral & frontal films in order to determine majorin the lateral & frontal films in order to determine major
dysplasias.dysplasias.
use of 3 ‘p’ suse of 3 ‘p’ s
Growth assessment of Physical morphologyGrowth assessment of Physical morphology
Search for Pathological PhenomenonSearch for Pathological Phenomenon
The interpretation of Physiologic condition.The interpretation of Physiologic condition.

(ii) DESCRIPTION(ii) DESCRIPTION
gives mathematical measurement & description .4 ‘c’ sgives mathematical measurement & description .4 ‘c’ s
Characterization or description comes first.Characterization or description comes first.
Comparison of one individual to another is made possibleComparison of one individual to another is made possible
Classification of factors.Classification of factors.
Communication of the problems.Communication of the problems.
(iii) GROWTH AND TREATMENT(iii) GROWTH AND TREATMENT
It is used to record and measure changes.It is used to record and measure changes.
(iv)(iv) PLANNING AHEADPLANNING AHEAD
Treatment PlanningTreatment Planning
More useful to make a “Cephalometric set up”More useful to make a “Cephalometric set up”

TRACING & IDENTIFICATION OFTRACING & IDENTIFICATION OF
CEPHALOMETRIC LANDMARKSCEPHALOMETRIC LANDMARKS
StepsSteps
 Soft tissue profile, external cranium, Vertebra.Soft tissue profile, external cranium, Vertebra.
 Cranial base, internal border of cranium, frontal sinus & earCranial base, internal border of cranium, frontal sinus & ear
rods.rods.
 Maxilla & related structures including nasal bone &Maxilla & related structures including nasal bone &
pterygomaxillary fissures.pterygomaxillary fissures.
 The mandible.The mandible.

CEPHALOMETRIC SUPERIMPOSITIONSCEPHALOMETRIC SUPERIMPOSITIONS
Growth and mechano therapy contribute to the outcomeGrowth and mechano therapy contribute to the outcome
of orthodontic treatment to different degrees.of orthodontic treatment to different degrees.
cephalometric superimpositions demonstrate the combinedcephalometric superimpositions demonstrate the combined
effects of growth and mechanotherapy.effects of growth and mechanotherapy.
Regional cephalometric superimpositions are performedRegional cephalometric superimpositions are performed
to evaluate three basic components of skeletal and dentoto evaluate three basic components of skeletal and dento
alveolar development:-maxillary ,mandibular and overallalveolar development:-maxillary ,mandibular and overall
facial changes.facial changes.
Superimposition of cranial base yields information aboutSuperimposition of cranial base yields information about
the movements of facial bones away from the cranialthe movements of facial bones away from the cranial
structures.structures.
Superimposition of maxillary structures can be used toSuperimposition of maxillary structures can be used to
evaluate changes in the maxillary dento alveolar complexevaluate changes in the maxillary dento alveolar complex
(PNS-ANS line).(PNS-ANS line).
Mandibular superimposition on relatively stableMandibular superimposition on relatively stable
anatomical structures can be used to evaluate dentoanatomical structures can be used to evaluate dento
alveolar changes.alveolar changes.

Methods of superimpositionMethods of superimposition
1.Superimposition on S-N at S.1.Superimposition on S-N at S.
2.Superimposition natural reference structures such as cranial2.Superimposition natural reference structures such as cranial
base.base.
3.Using a subtraction technique where a positive copy is3.Using a subtraction technique where a positive copy is
made of one of the radiographs and overlaid on the other.made of one of the radiographs and overlaid on the other.
Areas of radiograph where no change has taken placeAreas of radiograph where no change has taken place
appear uniformly grey.appear uniformly grey.
4.Using a “blink comparator”. Two radiographs are illuminated4.Using a “blink comparator”. Two radiographs are illuminated
alternately in rapid succession, giving an impression ofalternately in rapid succession, giving an impression of
the changes that have occurred between the radiographs.the changes that have occurred between the radiographs.
5.Using digital images tracings of cephalometric radiographs5.Using digital images tracings of cephalometric radiographs
can be superimposed either on landmarks or structurescan be superimposed either on landmarks or structures
that have out lined by the operator.that have out lined by the operator.

V. Gavel & L.Dermant (EJO – 2003).V. Gavel & L.Dermant (EJO – 2003).
To identify position of unerupted canine byTo identify position of unerupted canine by
using lateral cephalogram, 3 differentusing lateral cephalogram, 3 different
displacements were stimulated. 10 mm frontally,displacements were stimulated. 10 mm frontally,
10 mm sagitally, 5mm vertically.10 mm sagitally, 5mm vertically.
They concluded that the degree of vertical &They concluded that the degree of vertical &
sagittal displacement of the incisor point of thesagittal displacement of the incisor point of the
impacted canine, angulation, length of the teethimpacted canine, angulation, length of the teeth
measured on cephalogram appeared to give anmeasured on cephalogram appeared to give an
accurate representation.accurate representation.

COMPUTERIZED CEPHCOMPUTERIZED CEPH
With introduction of digital imaging, automated andWith introduction of digital imaging, automated and
semi-automated landmark identification directly from thesemi-automated landmark identification directly from the
digital images can be done. This would avoid thedigital images can be done. This would avoid the
• need for manual tracingneed for manual tracing
• removes operator subjectivityremoves operator subjectivity
but at present automated systems are unable to matchbut at present automated systems are unable to match
human operators in the accuracy of landmark identification.human operators in the accuracy of landmark identification.
Yi Jane chen et al (AO 2000), compared the traditionalYi Jane chen et al (AO 2000), compared the traditional
and computer aided digital cephalometric landmarks andand computer aided digital cephalometric landmarks and
concluded that the inter observer error for each landmarkconcluded that the inter observer error for each landmark
in digital images was generally larger than that in thein digital images was generally larger than that in the
original radiograph. Mostly seen in Po, Ar, ANS, UM.original radiograph. Mostly seen in Po, Ar, ANS, UM.

Automatic computerized radiographyAutomatic computerized radiography
identification of cephalometric Landmarks. Didentification of cephalometric Landmarks. D
J Rudolph et al.J Rudolph et al.
This study compared manual identification on aThis study compared manual identification on a
computer monitor and Spatial Spectrometrycomputer monitor and Spatial Spectrometry
automatic method for landmark identification onautomatic method for landmark identification on
minimum resolution image. Fifteen landmarksminimum resolution image. Fifteen landmarks
were selected on set of 14 test images. Thewere selected on set of 14 test images. The
results showed no statistical difference (p>0.05)results showed no statistical difference (p>0.05)
in mean landmark identification errors betweenin mean landmark identification errors between
manual identification on a computer display andmanual identification on a computer display and
automatic identification using SSautomatic identification using SS

THREE DIMENSIONAL CEPHALOMETRICTHREE DIMENSIONAL CEPHALOMETRIC
ANALYSISANALYSIS
It is a valuable tool in assessment of skeletal remodeling,It is a valuable tool in assessment of skeletal remodeling,
contour changes, and changes in proportion that occurcontour changes, and changes in proportion that occur
with aging. Computed assisting tomographic data can bewith aging. Computed assisting tomographic data can be
used in either coronal or axial direction.used in either coronal or axial direction.
Advantages:-Advantages:-
• Precise anatomic data unobtainable by other methodsPrecise anatomic data unobtainable by other methods
can be acquired from a 3D radiological image.can be acquired from a 3D radiological image.
• Improved diagnostic accuracy.Improved diagnostic accuracy.
• Contours & surface detail are rendered in fine detail.Contours & surface detail are rendered in fine detail.
• Ability to correlate soft tissue and hard tissue pointsAbility to correlate soft tissue and hard tissue points
directly on the computer.directly on the computer.
Constrains:-Constrains:-
Lack of uniformity in viewing the reconstructed image.Lack of uniformity in viewing the reconstructed image.www.indiandentalacademy.comwww.indiandentalacademy.com

MethodMethod:-:-
 Both axial & coronal slices were obtained.Both axial & coronal slices were obtained.
 Slice 3mm (or) less is used.Slice 3mm (or) less is used.
 CT scans were reconstructed in 3 D by reformattingCT scans were reconstructed in 3 D by reformatting
process.process.
Uses:-Uses:-
 Especially useful in patient with marked dentofacialEspecially useful in patient with marked dentofacial
asymmetries.asymmetries.
 To improve preoperative diagnostic capabilities includingTo improve preoperative diagnostic capabilities including
volumetric analysis.volumetric analysis.

XERORADIOGRAPHYXERORADIOGRAPHY
It is the process of recording a latent radiographicIt is the process of recording a latent radiographic
image on aimage on a selenium coated aluminum plate ,the image isselenium coated aluminum plate ,the image is
then transferred to a specially treated paper forthen transferred to a specially treated paper for
visualization. The whole process is fully automatic , takingvisualization. The whole process is fully automatic , taking
90 seconds to complete.90 seconds to complete.
AdvantagesAdvantages
1) Soft tissues, bone, teeth, and air passages are clearly1) Soft tissues, bone, teeth, and air passages are clearly
visible because of a large recording latitude , highvisible because of a large recording latitude , high
resolution and the “ edge enhancement phenomenon”resolution and the “ edge enhancement phenomenon”
2) more pronounced definition and contrast2) more pronounced definition and contrast
Davis and associates and Johnson concludeDavis and associates and Johnson conclude
Xeroradiography is superior to conventional radiographyXeroradiography is superior to conventional radiography

ORTHOPANTOMOGRAPHYORTHOPANTOMOGRAPHY
 It is a technique for producing a single tomographic imageIt is a technique for producing a single tomographic image
of the facial structures that includes both the maxillary andof the facial structures that includes both the maxillary and
mandibular arches and their supporting structures.mandibular arches and their supporting structures.
ADVANTAGESADVANTAGES
 Broad coverage of the facial bones & teeth.Broad coverage of the facial bones & teeth.
 Low pt radiation doseLow pt radiation dose..
 Convenience of the examination for the pt.Convenience of the examination for the pt.
 Ability to be used in pts unable to open their mouth.Ability to be used in pts unable to open their mouth.
 DISADVANTAGESDISADVANTAGES
 Unequal magnification.Unequal magnification.
 Geometric distortion.Geometric distortion.

INDICATIONSINDICATIONS
 Need to know the State of the dentition and the presence /Need to know the State of the dentition and the presence /
absence of teeth.absence of teeth.
 Unerupted tooth.Unerupted tooth.
 Periodontal tooth support.Periodontal tooth support.
 Destructive disease of the articular surface of TMJ.Destructive disease of the articular surface of TMJ.
PRINCIPLEPRINCIPLE
 Two adjacent disks rotate at the same speed in oppositeTwo adjacent disks rotate at the same speed in opposite
direction as an X Ray beam passes through their centers ofdirection as an X Ray beam passes through their centers of
rotation.rotation.
IMAGE LAYERIMAGE LAYER
 It is a 3 – dimensional curved zone (focal trough) in whichIt is a 3 – dimensional curved zone (focal trough) in which
the structures lying with in the layer are reasonably wellthe structures lying with in the layer are reasonably well
defined on final panoramic image.defined on final panoramic image.

PATIENT POSITIONINGPATIENT POSITIONING
Mid sagital plane must be centered with in the image layer.Mid sagital plane must be centered with in the image layer.
Patient ‘s chin and occlusal plane is aligned so that it is lowerPatient ‘s chin and occlusal plane is aligned so that it is lower
anteriorly, angled 20-30 degrees below the horizontal plane. Lineanteriorly, angled 20-30 degrees below the horizontal plane. Line
from the tragus of the ear to the outer canthus of the eye isfrom the tragus of the ear to the outer canthus of the eye is
parallel with the floor.parallel with the floor.
POSITIONING ERRORPOSITIONING ERROR
1) Pt. too far from the film. Ant teeth magnified in1) Pt. too far from the film. Ant teeth magnified in
width and out of focus.width and out of focus.
2) Pt. too close to the film Ant teeth narrowed and out2) Pt. too close to the film Ant teeth narrowed and out
of focus.of focus.
3) Pt. Asymmetrically turned Post teeth enlarge on one3) Pt. Asymmetrically turned Post teeth enlarge on one
right or leftright or left side and decreased on otherside and decreased on other
side.side.
4) Pts. Wearing earrings Artefactual shadow.4) Pts. Wearing earrings Artefactual shadow.
5) Failure to instruct the pt5) Failure to instruct the pt Vertical (or) horizontalVertical (or) horizontal
to keep still throughout distortion of the partto keep still throughout distortion of the part
the cyclethe cycle of the image being producedof the image being produced
at the time of the movement.at the time of the movement.

SPECIALISED IMAGING TECHNIIQUESSPECIALISED IMAGING TECHNIIQUES
 Conventional tomographyConventional tomography
 StereoscopyStereoscopy
 ScanographyScanography
 Computed tomographyComputed tomography
 Magnetic resonance ImagingMagnetic resonance Imaging
 UltrasonographyUltrasonography
 ArthrographyArthrography
 Digital radiographyDigital radiography

COMPUTED TOMOGRAPHYCOMPUTED TOMOGRAPHY
 CT image is a display of a thin slice of the body, developedCT image is a display of a thin slice of the body, developed
from multiple X ray absorption measurements madefrom multiple X ray absorption measurements made
around the periphery.around the periphery.
ADVANTAGES:-ADVANTAGES:-
 Cross Sectional ImageCross Sectional Image
 Superior contrast resolutionSuperior contrast resolution
 Geometric accuracyGeometric accuracy
 Tissue CharacterizationTissue Characterization
 Image windowingImage windowing
 Digital image processingDigital image processing
 Quick and Non invasiveQuick and Non invasive

 Xenon CT – To study blood flow.Xenon CT – To study blood flow.
 Quantitative CT – Determination of bone mineral content.Quantitative CT – Determination of bone mineral content.
 Dynamic CT (Rapid sequence CT) - to study physiology.Dynamic CT (Rapid sequence CT) - to study physiology.
 High Speed resolution CTHigh Speed resolution CT..
LIMITATIONSLIMITATIONS
 High dose of radiationHigh dose of radiation..
 Geometric (or) Contrast missGeometric (or) Contrast miss..
 ArtifactsArtifacts..
 Bone lesions affecting the TMJBone lesions affecting the TMJ..
 Implant planningImplant planning..
COMPONENTSCOMPONENTS
 Gantry – Consists of a) Detector arrayGantry – Consists of a) Detector array
b) X Ray sourceb) X Ray source..
c) Pt. Support couchc) Pt. Support couch..
 ComputerComputer..
 Control console – This allows the operator to dictate theControl console – This allows the operator to dictate the
parameters of the CT scanparameters of the CT scan..

IMAGE ACQUISITIONIMAGE ACQUISITION
CT images are acquiredCT images are acquired
in the axial, coronal, orin the axial, coronal, or
sagital planes. Thesesagital planes. These
images are taken inimages are taken in
succession and aresuccession and are
generally referred to asgenerally referred to as
slices. The informationslices. The information
form these multiple slicesform these multiple slices
can then be reformatted tocan then be reformatted to
produce images in otherproduce images in other
planes.planes.

CT NUMBERS OR HOUNSFIELDCT NUMBERS OR HOUNSFIELD
UNITSUNITS
The numeric data in eachThe numeric data in each
pixel is called a CT number.pixel is called a CT number.
The CT number corresponds toThe CT number corresponds to
the linear attenuationthe linear attenuation
coefficient of a particular tissuecoefficient of a particular tissue
at a designated kilo voltage.at a designated kilo voltage.
Air = -1000Air = -1000
Fat = -100Fat = -100
Water = -0Water = -0
CSF = +1CSF = +1
Muscle = +50Muscle = +50
Bone = +1000Bone = +1000

Gary yip et al (seminarGary yip et al (seminar
in ortho 2004).in ortho 2004).
Concluded that microConcluded that micro
tomography is particularlytomography is particularly
useful for the technicallyuseful for the technically
demanding task of assessingdemanding task of assessing
mineral density patterns ofmineral density patterns of
bone, supporting titaniumbone, supporting titanium
implants.implants.
The expediency,The expediency,
nondestructive nature, & 3Dnondestructive nature, & 3D
imagery of this techniqueimagery of this technique
used to evaluate quantity,used to evaluate quantity,
quality & mechanicalquality & mechanical
properties of bone.properties of bone.

MAGNETIC RESONANCE IMAGINGMAGNETIC RESONANCE IMAGING
(MRI)(MRI)
Discovered by Purcell and Loch in 1946.Discovered by Purcell and Loch in 1946.
PRINCIPLE:PRINCIPLE:
 MRI uses non-ionizing radiation from theMRI uses non-ionizing radiation from the
radiofrequency (RF) band of the Electromagneticradiofrequency (RF) band of the Electromagnetic
spectrum.spectrum.
 Unpaired Neutron/ProtonUnpaired Neutron/Proton  Magnetic DipolesMagnetic Dipoles
in biological tissues- H2 atom is the mostin biological tissues- H2 atom is the most
common.common.
 Natural state – Net magnetization is zero.Natural state – Net magnetization is zero.
 Application of External Magnetic fieldApplication of External Magnetic field..
• Spin-up (Lower energy state)Spin-up (Lower energy state)..
• Spin -down (Higher energy state )Spin -down (Higher energy state )..
 MRI reflects the magnetic properties of mobile H2.

IMAGING PROCESS
1)Patient placed in the magnetic field.
The protons act like small magnets ,align themselves with in the
magnetic field and begin to rotate at a precise frequancy. This is
called ‘Precession’ ( Larmor Frequency)
Protons align in external magnetic field.a new magnetic
vector is induced. That is Net Magnetic vector in Longitudinal
Magnetization
Superconductive magnet – field strength 0.1 – 2 Telsa.
2)Radio wave sent in.
New Magnetic vector excited by RF wave.
Tipping of Bulk magnetic vector in space.
Duration of RF wave determinates Angle of tip.
the tipping of new magnetic vector results in a decrease in its
size and a new magnetic vector- Transverse Magnetization
appears.
3)Radio wave turned off.
Protons calm down/relax to original position.
Recovery via T1 & T2 relaxation times.

4)Patient emits signal ( as T1, T2).4)Patient emits signal ( as T1, T2).
Rotation of bulk magnetic vector to pre-excitation stateRotation of bulk magnetic vector to pre-excitation state 
Induction of electric current in wire coils .Signal received andInduction of electric current in wire coils .Signal received and
processed.processed.
T1T1  measures the longitudinal return of protons to align with themeasures the longitudinal return of protons to align with the
external magnet after the RF pulse has stopped.external magnet after the RF pulse has stopped.
Small water molecules takes long time to transfer energy.leads toSmall water molecules takes long time to transfer energy.leads to
long T1- appear black on T1 weighted images.long T1- appear black on T1 weighted images.
Larger fat molecules-shorter T1- White or Bright.Larger fat molecules-shorter T1- White or Bright.
T1 - Shows AnatomyT1 - Shows Anatomy
T2T2  measures the energy transfer between interacting protonsmeasures the energy transfer between interacting protons
after excitation. For water, CSF, saliva – Long T2 – White orafter excitation. For water, CSF, saliva – Long T2 – White or
bright. For fat – short T2 – bright signal suppressed.bright. For fat – short T2 – bright signal suppressed.
T2 - Shows PathologyT2 - Shows Pathology
5)Reconstruction of picture.5)Reconstruction of picture.
Most common –spin echo pulse sequenceMost common –spin echo pulse sequence
Application of RF pulses-localization of signals-FourierApplication of RF pulses-localization of signals-Fourier
transformation-reconstruction of image.transformation-reconstruction of image.

MR CONTRAST AGENTMR CONTRAST AGENT
 Injected contrast agents change the signal intensity byInjected contrast agents change the signal intensity by
altering T 1 and T 2 relaxation times. Paramagnetic Gd-altering T 1 and T 2 relaxation times. Paramagnetic Gd-
DTPA-Most popular (Gaddolinium diethyleneDTPA-Most popular (Gaddolinium diethylene
Triamine pantothenic acid).Triamine pantothenic acid).
SAFETY CONSIDERATIONSSAFETY CONSIDERATIONS
 Contraindicated in pts with Ferromagnetic materialsContraindicated in pts with Ferromagnetic materials
like Cardiac pacemaker.like Cardiac pacemaker.
 Safety in Pregnancy not established.Safety in Pregnancy not established.

 It offers best resolution of tissues of low inherentIt offers best resolution of tissues of low inherent
contrast.contrast.
 No ionizing radiation in involved with MRI.No ionizing radiation in involved with MRI.
 Because e at the region of the body Imaged in MRI inBecause e at the region of the body Imaged in MRI in
controlled electronically, direct multiplannar imaging iscontrolled electronically, direct multiplannar imaging is
possible without reorienting the patient.possible without reorienting the patient.
DIS ADVAVTAGESDIS ADVAVTAGES
 Relatively long imaging times and the potential hazardRelatively long imaging times and the potential hazard
imposed by the presence of ferromagnetic metals in theimposed by the presence of ferromagnetic metals in the
vicinity of the imaging magnet.vicinity of the imaging magnet.
 Ex – Cardiac pacemakers, cerebral aneurysm clipsEx – Cardiac pacemakers, cerebral aneurysm clips
 Some patients suffer from claustrophobia whenSome patients suffer from claustrophobia when
positioned in a MRI Machine.positioned in a MRI Machine.
 It gives excellent soft tissue contrast resolution.It gives excellent soft tissue contrast resolution.
 Diagnosing a suspected internal derangement of theDiagnosing a suspected internal derangement of the
TMJ and evaluating the treatment of that derangementTMJ and evaluating the treatment of that derangement
after surgery.after surgery.
 Identifying and Localizing orofacial soft tissue lesions.Identifying and Localizing orofacial soft tissue lesions.
 Gives Images of salivary gland parenchyma.Gives Images of salivary gland parenchyma.

Using Magnetic resonance imaging, temporo mandibularUsing Magnetic resonance imaging, temporo mandibular
joint Effects of activator treatment are analyzed by Sabinejoint Effects of activator treatment are analyzed by Sabine
et al , Angle Orthodontist 6; 72, 2002 he concluded theet al , Angle Orthodontist 6; 72, 2002 he concluded the
following:following:
During the one year treatment period the sagital dentalDuring the one year treatment period the sagital dental
arch relationship improved .On average, the physiologicarch relationship improved .On average, the physiologic
position of disc, condyle and fossa was present bothposition of disc, condyle and fossa was present both
present and after one year activator treatment.present and after one year activator treatment.
A pretreatment physiological disc condyle relationshipA pretreatment physiological disc condyle relationship
was unaffected by activator therapy. The prevalence of subwas unaffected by activator therapy. The prevalence of sub
clinical capsulitis of the inferior stratum of posteriorclinical capsulitis of the inferior stratum of posterior
attachment during activator treatment.attachment during activator treatment.
Using magnetic resonance imaging and cephalometricUsing magnetic resonance imaging and cephalometric
investigation , temporo mandibular joint remodeling ininvestigation , temporo mandibular joint remodeling in
adolescent and young adults during Herbst treatment wasadolescent and young adults during Herbst treatment was
analyzed by sabine et alanalyzed by sabine et al
The increase in mandibular prognatism accomplishedThe increase in mandibular prognatism accomplished
by Herbst therapy is found to be a result of codylar andby Herbst therapy is found to be a result of codylar and
glenoid fossa remodeling.glenoid fossa remodeling.

ULTRASONOGRAPHYULTRASONOGRAPHY
The phenomenon perceived as sound is the result ofThe phenomenon perceived as sound is the result of
periodic changes in the pressure of air against the eardrum.periodic changes in the pressure of air against the eardrum.
Periodicity of these changes lies anywhere between 1500 andPeriodicity of these changes lies anywhere between 1500 and
20,000 cycles per second.20,000 cycles per second.
PRINCIPLEPRINCIPLE
 Electrical impulses generated by the scanner causes theElectrical impulses generated by the scanner causes the
dipoles in the crystal to realign themselves and to thedipoles in the crystal to realign themselves and to the
electrical field and thus suddenly change the crystal’selectrical field and thus suddenly change the crystal’s
thickness. This abrupt change begins a series of vibrationsthickness. This abrupt change begins a series of vibrations
that produce the sound waves that are transmitted in to thethat produce the sound waves that are transmitted in to the
tissues being examined.tissues being examined.
 Does not require special facilities.Does not require special facilities.
 Can be used to view the joint in a continuum with outCan be used to view the joint in a continuum with out
invasion, discomfort.invasion, discomfort.
DISADVANTAGESDISADVANTAGES
 Noise signal.Noise signal.
 Size of the transducer.Size of the transducer.
 Meniscus not seen.Meniscus not seen. www.indiandentalacademy.comwww.indiandentalacademy.com

Chien_Lun peng et al (EJO – 2003).Chien_Lun peng et al (EJO – 2003).
To differentiate infantile and mature swallow. He usedTo differentiate infantile and mature swallow. He used
B +ve mode ultrasonography movements of the tongue tipB +ve mode ultrasonography movements of the tongue tip
& submental musculature during swallowing were recorded& submental musculature during swallowing were recorded
on video cassette.on video cassette.
It provides a noninvasive visualization of tongueIt provides a noninvasive visualization of tongue
movements & no foreign body is required in the oral cavitymovements & no foreign body is required in the oral cavity
allowing more natural swallowing behaviour.allowing more natural swallowing behaviour.

DIGITAL RADIOGRAPHYDIGITAL RADIOGRAPHY
 A digital image is a matrix of square pieces or picture elementsA digital image is a matrix of square pieces or picture elements
(pixels), that form a mosaic pattern from wherein original image can(pixels), that form a mosaic pattern from wherein original image can
be reconstructed for visual display.be reconstructed for visual display.
Analog Image Digital ImageAnalog Image Digital Image
 1) Conventional radiographic 1) a) Light sensitive1) Conventional radiographic 1) a) Light sensitive
ImageImage elements to recordelements to record
the image.the image.
b) Shades of gray tob) Shades of gray to
display the Imagedisplay the Image
 2) Silver halide grain 2) Light sensitive2) Silver halide grain 2) Light sensitive
elementselements
 3) Randomly dispersed 3) Regular grid of rows3) Randomly dispersed 3) Regular grid of rows
and Columnsand Columns
 4) Continuous Spectrum 4) Numeric and Discrete.4) Continuous Spectrum 4) Numeric and Discrete.

PIXELS AND VOXELSPIXELS AND VOXELS
 PixelPixel
2-D Digital Images – Composed of Picture elements.2-D Digital Images – Composed of Picture elements.
 VoxelVoxel
3-D Digital Images – Composed of volume elements.3-D Digital Images – Composed of volume elements.
PRODUCTION OF DIGITAL IMAGEPRODUCTION OF DIGITAL IMAGE
Analog to Digital conversion (ADC).Analog to Digital conversion (ADC).
 Sampling - Small range of voltage values groupedSampling - Small range of voltage values grouped
together.together.
 Quantization - Every sampled signal is assigned a value.Quantization - Every sampled signal is assigned a value.
Pixels are arranged in proper locations and given aPixels are arranged in proper locations and given a
shade of gray corresponding to quantizationshade of gray corresponding to quantization
number.number.

ADVANTAGES OF DIGITAL RADIOLOGYADVANTAGES OF DIGITAL RADIOLOGY
 Reduces time and effort needed for chemical processingReduces time and effort needed for chemical processing
error.error.
 Eliminates faulty radiographs due to processing error.Eliminates faulty radiographs due to processing error.
 Eases image transfer for electronic communication.Eases image transfer for electronic communication.
 Eases storage, back up and retrieval.Eases storage, back up and retrieval.
 Permits computed optimization at image.Permits computed optimization at image.
 Facilities pt communication.Facilities pt communication.
 Lowers radiation dose to the pt.Lowers radiation dose to the pt.
 Ability to manipulate image contrast and density.Ability to manipulate image contrast and density.
 Initial expenditure high.Initial expenditure high.
 X-ray receptor in IO systems –susceptible to roughX-ray receptor in IO systems –susceptible to rough
handling.handling.
 Risk of system becomes obsolete.Risk of system becomes obsolete.

 Single step systemSingle step system (CCD/C MOS).(CCD/C MOS).
 2 step wireless system2 step wireless system (PSP Plated).(PSP Plated).
CCD (Charge coupled device)CCD (Charge coupled device)
 The CCD uses a thin wafer of silicon as theThe CCD uses a thin wafer of silicon as the
basis for image recording.basis for image recording.
 Associated read out and amplifyingAssociated read out and amplifying
electronics.electronics.
 Scintillating layer-Gadolinium oxybromide orScintillating layer-Gadolinium oxybromide or
cesium iodide.cesium iodide.

IMAGE PRODUCTION IN CCD SENSORIMAGE PRODUCTION IN CCD SENSOR
RadiationRadiation
Breakage of silicon bondsBreakage of silicon bonds
Production of electron hole pairsProduction of electron hole pairs
Creation of Charge pocketsCreation of Charge pockets
Charge pocket in each pixelCharge pocket in each pixel
forms latent imageforms latent image
Bucket brigade transferBucket brigade transfer
Read out amplifierRead out amplifier
ADC IMAGEADC IMAGEwww.indiandentalacademy.comwww.indiandentalacademy.com

 It is a part of the direct sensor system. Image is displayedIt is a part of the direct sensor system. Image is displayed
on the monitor in a few seconds.on the monitor in a few seconds.
 It has the lowest noise.It has the lowest noise.
 Bulk of the sensor.Bulk of the sensor.
 Electronic cable is necessary to transfer the data from theElectronic cable is necessary to transfer the data from the
senior to the ADC.senior to the ADC.
 Detectors are expensive.Detectors are expensive.

C-MOS (Complementary Metal oxideC-MOS (Complementary Metal oxide
SemiconductorSemiconductor
sensors)sensors)
It is also silicon-based semiconductors.It is also silicon-based semiconductors.
ADANTAGESADANTAGES
 ““Design Integration”.Design Integration”.
 ADC control functions are built in with in the sensor.ADC control functions are built in with in the sensor.
 Easy manufacturability.Easy manufacturability.
 Less expensive than CCD.Less expensive than CCD.
 C-Mos sensors may not perform well in low light conductors.C-Mos sensors may not perform well in low light conductors.
 More noise than CCD.More noise than CCD.
 Less active area for image acquisition than CCD sensors.Less active area for image acquisition than CCD sensors.

2 STEP WIRELESS SYSTEM2 STEP WIRELESS SYSTEM
PSP plates (PhosphostimulablePSP plates (Phosphostimulable
phosphor plates)phosphor plates)
COMPOSITIONCOMPOSITION
Contains “Europium – doped” BariumContains “Europium – doped” Barium
fluorohalidefluorohalide
europium creates imperfections.europium creates imperfections.
PRINCIPLESPRINCIPLES
PHOSPHORESENCEPHOSPHORESENCE  Quantified as a measure of XQuantified as a measure of X
ray energy absorbed byray energy absorbed by
materialmaterial

IMAGE FORMATIONIMAGE FORMATION RadiationRadiation  movement of Valance electron into Conductionmovement of Valance electron into Conduction
bandband  migration into nearby Halogen vacanciesmigration into nearby Halogen vacancies
(‘F’ Centers)(‘F’ Centers) Formation of Latent images.Formation of Latent images.
 Stimulation by Red lightStimulation by Red light  Return of electrons into the ValenceReturn of electrons into the Valence
bandband  Release of energy in green spectrumRelease of energy in green spectrum  Fibro opticsFibro optics 
Photomultiplier tubePhotomultiplier tube  Conversion of light into ElectricalConversion of light into Electrical
energy. Removal of stimulatory light by Red filterenergy. Removal of stimulatory light by Red filter 
conversion of remaining green light into varying voltage—conversion of remaining green light into varying voltage—
Quantification in ADCQuantification in ADC  Storage and display.Storage and display.

 It can be used indefinitely.It can be used indefinitely.
 Can be used with existing sources.Can be used with existing sources.
 Linear or Logarithmic response to radiation.Linear or Logarithmic response to radiation.
 Wide exposure range.Wide exposure range.
 High Initial cost.High Initial cost.
 Poor spatial resolution.Poor spatial resolution.
INDICATIONINDICATION
 Caries detection.Caries detection.
 Alveolar bone imaging.Alveolar bone imaging.
 To study trabecular Pattern of jaw bones.To study trabecular Pattern of jaw bones.
 Cephalometric radiography.Cephalometric radiography.

IMAGE QUALITY CONSIDERATIONSIMAGE QUALITY CONSIDERATIONS
• Active area.Active area.
• Signal to noise ratio.Signal to noise ratio.
• Contrast resolution.Contrast resolution.
• Spatial resolutions.Spatial resolutions.
• Radiation dose.Radiation dose.
• Detector latitude.Detector latitude.
• Detector sensitivity.Detector sensitivity.

TMJ PROJECTIONSTMJ PROJECTIONS
HARD TISSUEHARD TISSUE
PANORAMIC PROJECTIONPANORAMIC PROJECTION
 Gross osseous changes in the condyle may be identified.Gross osseous changes in the condyle may be identified.
 Ex – Asymmetries, extensive erosions changes in articularEx – Asymmetries, extensive erosions changes in articular
eminance.eminance.
TRANSCRANIAL PROJECTIONTRANSCRANIAL PROJECTION
 Lateral aspect of the condyle, and temporal component andLateral aspect of the condyle, and temporal component and
range of motion.range of motion.
TRANSPHARYNGEAL (PARMA) PROJECTIONTRANSPHARYNGEAL (PARMA) PROJECTION
 Sagital view of the medial pole of the condyle.Sagital view of the medial pole of the condyle.
 Erosive changes of the condyle.Erosive changes of the condyle.

SUBMENTOVERTEX VIEWSUBMENTOVERTEX VIEW
• skull base and condyles superimposed on the condylarskull base and condyles superimposed on the condylar
necks and mandibular raminecks and mandibular rami
• Facial asymmetries, condylar displacement, rotation of theFacial asymmetries, condylar displacement, rotation of the
mandible.mandible.
CONVENTIONAL TOMOGRAPHYCONVENTIONAL TOMOGRAPHY
• erosive changes of the condyleerosive changes of the condyle
• Entire condylar head is visible in the mediolateral planeEntire condylar head is visible in the mediolateral plane
• Depicting true condylar position and revealing osseousDepicting true condylar position and revealing osseous
changeschanges
COMPUTED TOMOGRAPHYCOMPUTED TOMOGRAPHY
• Gives 3 dimensional shape and internal structure of theGives 3 dimensional shape and internal structure of the
osseous components of the joint and soft tissueosseous components of the joint and soft tissue
structuresstructures www.indiandentalacademy.comwww.indiandentalacademy.com

TMJ SOFT TISSUETMJ SOFT TISSUE
ARTHROGRAPHYARTHROGRAPHY
• Information about disk position, function, morphologyInformation about disk position, function, morphology
and integrity of diskal attachments.and integrity of diskal attachments.
MRIMRI
• demonstrate osseous and diskal tissues.demonstrate osseous and diskal tissues.
• Inflammation and joint effusionInflammation and joint effusion
• MEDIAL DISK displacement are best detected.MEDIAL DISK displacement are best detected.

MAXILLARY CANINE IMPACTIONMAXILLARY CANINE IMPACTION
In RadiographIn Radiograph
• To determine size and shape of the teeth.To determine size and shape of the teeth.
• To determine position of the teeth.To determine position of the teeth.
CANINE LOCALISATIONCANINE LOCALISATION
Parallax in horizontal plane.Parallax in horizontal plane.
Required Radiography :Required Radiography :
 2 IOPA2 IOPA
 Upper occlusal.Upper occlusal.
Parallax in Vertical Plane.Parallax in Vertical Plane.
 OPGOPG
 Upper occlusal.Upper occlusal.

Vertex occlusalVertex occlusal
 X-Ray Tube is positioned above the patient , inX-Ray Tube is positioned above the patient , in
the mid line, aiming downwards through thethe mid line, aiming downwards through the
vertex of the skull.vertex of the skull.
 Buccal or palatal position of an unerupted teethBuccal or palatal position of an unerupted teeth
can be identified.can be identified.
 Dis Adv: Radiation to eyes, gonads andDis Adv: Radiation to eyes, gonads and
pitutarygland.pitutarygland.
True lateral & PA Jaws.True lateral & PA Jaws.
Steroscopic Views.Steroscopic Views.
Cross sectional spiralCross sectional spiral
tomography.tomography.www.indiandentalacademy.comwww.indiandentalacademy.com

CONCLUSION
Radiology is one of the rapidly changing field in diagnostic imaging.
Systematic approach is necessary to evaluate the complex
anatomical relationships displayed on the CT & MRI and other
specialized images.
For a long time, radiographic film was the most important medium
with which to acquire & archive the diagnostic image.
In the future conventional radiographs will become obsolete and will
be replaced by digital images.

Cephalometric landmarks

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Cephalometric landmarks

Similar to Cephalometric landmarks (20)

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Cephalometric landmarks