radiology in orthodontics-dr.kavitha / orthodontic courses by indian dental academy

RADIOLOGY IN ORTHODONTICSRADIOLOGY IN ORTHODONTICS

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INDIAN DENTAL ACADEMY

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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


INTRODUINTRODUCTIONCTION

The use of X Rays in an integral part of clinical The use of X Rays in an integral part of clinical dentistry with some form of radiographic examination dentistry 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 main radiographs 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 radiation X Rays are form of high energy electromagnetic radiation & part of electromagnetic spectrum, which also includes & part of electromagnetic spectrum, which also includes low energy radio waves, television & visible light. low 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 SupplyFunctionsFunctions

1. Provide low – voltage current to heat the X Ray tube 1. 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 anode 2. 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 RADIATION BREMSSTRAHLUNG RADIATION..

IfIf High speed electrons hits the nuclei High speed electrons hits the nuclei of a target atom, all its kinetic energy is of 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 is The energy of the resultant photon is numerically equal to the energy of the numerically equal to the energy of the electron.electron.

II. II. CHARACTERISTIC RADIATONCHARACTERISTIC RADIATON..

It occurs when an electron from a It occurs when an electron from a filament displaces an electron from a filament displaces an electron from a shell of a tungsten target atom. When shell of a tungsten target atom. When the displaced electron is replaced by the the displaced electron is replaced by the outer-shell electron, a PHOTON is outer-shell electron, a PHOTON is emitted with an energy equivalent to the emitted with an energy equivalent to the difference in the two orbital binding difference in the two orbital binding energies.energies. www.indiandentalacademy.comwww.indiandentalacademy.com

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 = No No of photons generated of 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 energyMaximal energy.Maximal energy.Bramsstrahlung photons. Bramsstrahlung photons.

Quality control.Quality control.


FILTRATIONFILTRATION To reduce the pTo reduce the patient dose, the less penetrating photons atient dose, the less penetrating photons

should be removed. This can be accomplished by placing a should 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 therefore Used 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 quantity Determining the quantity of radiation exposure (or) dose.of radiation exposure (or) dose.

UNITS OF MEASUREMENTUNITS OF MEASUREMENT:-:-

Quantity Quantity SI Unit SI Unit Traditional UnitTraditional Unit

(a) Exposure(a) Exposure C/Kg C/Kg Roentgen Roentgen (b) Absorbed Dose Gray(b) Absorbed Dose Gray RadRad(c) Equivalent (or)(c) Equivalent (or)

effective doseeffective dose Sievert Sievert RemRem(d) Radioactivity(d) Radioactivity Becquerel (Bg) Becquerel (Bg) Curie Curie


IMAGE RECEPTORS (FILMIMAGE RECEPTORS (FILM)) Composition:-Composition:-

(i) Emulsion (i) Emulsion (ii) (ii) BaBasese

EmulsionEmulsion - It is sensitive to X - It is sensitive to X Rays & visible light, Rays & visible light, records the radiographic records the radiographic Image.Image.

BaseBase - it is a plastic supporting - it is a plastic supporting

material on to which the material on to which the emulsion is coated.emulsion is coated.

TypesTypes direct actions or non direct actions or non

screen film ex- IOPAscreen film ex- IOPA indirect actions or screen indirect actions or screen

film ex- extra oral film film ex- extra oral film ( it is used in combination ( it is used in combination with intensifying screen)with intensifying screen)


INTENSIFYING SCREENINTENSIFYING SCREEN It transfers X-Ray energy into visible light and this in turn exposes the screen films. So less radiation exposure and less radiation time is required.It transfers X-Ray energy into visible light and this in turn exposes the screen films. So less radiation exposure and less radiation time is required.Base Base

These are made up of polyester plastic measures .25mmthickness.These are made up of polyester plastic measures .25mmthickness.It provides mechanical support for the screen.It provides mechanical support for the screen.

Reflecting layerReflecting layerIt is a white layer of It is a white layer of

titanium dioxide coated on the titanium dioxide coated on the base lies beneath the phosphor base lies beneath the phosphor layer. It reflects any light emitted layer. It reflects any light emitted from the phosphor layer back to from the phosphor layer back to the X-Ray film.the X-Ray film.Phosphor layerPhosphor layer It consists of light sensitive It consists of light sensitive phosphor crystals suspended in a phosphor crystals suspended in a plastic material. When phosphors plastic material. When phosphors are struck by photons, they are struck by photons, they fluorescence i.e they emit visible fluorescence i.e they emit visible light photons that exposes X-ray light photons that exposes X-ray film.film.


Most common phosphor used areMost common phosphor used are

Calcium tungstate that fluorescence in blue portion of Calcium 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 fluorescence Thulium 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 a They 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 IMAGE RADIOGRAPHIC IMAGE CHARACTERSTICSCHARACTERSTICS

(i) (i) Radiographic DensityRadiographic Density -- Exposure time (x) Exposure time (x) Subject ThicknessSubject Thickness∞ ∞ Subject Density Subject Density

(ii) (ii) Contrast Contrast -- Subject contrast Subject contrast (Subject’s (Subject’s thickness, thickness, density and density and

atomic no)atomic no)Film contrast (Intensity Film contrast (Intensity

of of the remnant beam)the remnant beam)Scattered radiation.Scattered radiation.

(iii) (iii) Radiographic SpeedRadiographic Speed Fast film requires Fast film requires -- exposureexposureSlowSlow - - 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 and Radiation effects at the tissue and organ levelorgan level

The radio sensitivity of a tissue or organ is The radio sensitivity of a tissue or organ is measured by its response to radiation.measured by its response to radiation.Short term effects Short term effects

Of radiation on a tissue is determined primarily Of radiation on a tissue is determined primarily by the sensitivity of its parenchymal cells. Cells by 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 the Extent of cell loss depends on – damage to the stem cell pools & proliferative rate of cell stem cell pools & proliferative rate of cell population.population.Long term effectsLong term effects

The long term deterministic effects of radiation The long term deterministic effects of radiation on tissues and organs depend primarily on the on tissues 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 tissuesOral mucous membraneOral mucous membrane• mucositis mucositis • secondary candida albicans infectionsecondary candida albicans infection• long term – atrophic changes due to progressive long 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 5.5Ph ↓ to 5.5• Progressive fibrosis, adiposis, loss of fine vasculature Progressive fibrosis, adiposis, loss of fine vasculature

and parenchymal degenerationand parenchymal degenerationTeeth Teeth • radiation cariesradiation caries..

Bone Bone • Normal marrow may be replaced with fatty marrow and Normal marrow may be replaced with fatty marrow and

fibrous connective tissue fibrous 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 oral I Intra oral -- IOPA, Bitewing, Occlusal.IOPA, Bitewing, Occlusal.II Extra OralII Extra Oral -- Oblique lateral, various Oblique lateral, various skull projections OPG.skull projections OPG.

INTRA ORAL PERIAPICAL RADIOGRAPHINTRA ORAL PERIAPICAL RADIOGRAPH:-:-

It shows 2 to 4 teeth & provides detailed information It 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 teeth the long axis of the teeth by film holder & the central by film holder & the central beam in directed at right beam in directed at right angle to the teeth & the angle to the teeth & the filmfilm

– – To further reduce To further reduce geometric distortion X Ray geometric distortion X Ray source be located source be located relatively distant from the relatively distant from the teeth. teeth. www.indiandentalacademy.comwww.indiandentalacademy.com

BISECTING ANGLE TECHBISECTING ANGLE TECH

• Based on the simple geometric Based on the simple geometric theorem (i.e.) (ieszynski’s rule theorem (i.e.) (ieszynski’s rule of isometry), which states the 2 of isometry), which states the 2 angles are equal when they angles are equal when they share one complete side & share one complete side & have 2 equal angles. have 2 equal angles.

• The plane of the film & long axis of the teeth form an The plane of the film & long axis of the teeth form an

angle with its apex at the point where the film is in angle with its apex at the point where the film is in contact with the teeth. When this angle is bisected contact with the teeth. When this angle is bisected

by an by an imaginary line or plane, 2 congruent angles with a imaginary line or plane, 2 congruent angles with a

common side (Imaginary bisector) formed. central ray is common side (Imaginary bisector) formed. central ray is directed at a right angle to the plane that bisects the directed at a right angle to the plane that bisects the angle angle between the long axis at the tooth & the film. between the long axis at the tooth & the film.


OBJECT LOCALIZATIONOBJECT LOCALIZATION

TUBE SHIFT TECHNIQUE (Buccal TUBE SHIFT TECHNIQUE (Buccal object rule, Clark' rule)object rule, Clark' rule)

The relative positions of radiographic The relative positions of radiographic images of two separate objects change images of two separate objects change when the projection angle at which the when the projection angle at which the images were is changed.images were is changed.

If the object in question appears to If the object in question appears to move in the same direction with respect move in the same direction with respect to the reference structures as does the to the reference structures as does the X-ray tube, it is on the lingual aspect of X-ray tube, it is on the lingual aspect of the reference object.the reference object.

If it appears to move in the opposite If it appears to move in the opposite direction of the X-ray tube, it is on the direction of the X-ray tube, it is on the buccal aspect. If it does not move with buccal aspect. If it does not move with respect to the reference object ,it lies at respect to the reference object ,it lies at the same depth (in the same vertical the same depth (in the same vertical plane) as the reference object plane) as the reference object


RIGHT ANGLE TECHNIQUERIGHT ANGLE TECHNIQUE

Two projections taken at Two projections taken at right angles to one another right angles to one another localize an object. In localize an object. In clinical practice the clinical practice the position of an object on position of an object on each radiograph is noted each radiograph is noted relative to the anatomical relative to the anatomical land marks. This allows an land marks. This allows an observer to determine the observer to determine the position of the object or an position 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 occlusal A rotational panoramic radiograph with an ant occlusal radiograph is a preferred combination of radiographs to radiograph is a preferred combination of radiographs to localize unerupted mandibular anterior teeth. This localize unerupted mandibular anterior teeth. This combination uses a tube shift in the vertical plane. The combination uses a tube shift in the vertical plane. The rotational panoramic radiograph is taken at an effective rotational panoramic radiograph is taken at an effective angle of +7°C to the occlusal plane & anterior occlusal angle 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 canines was States that localization of ectopic maxillary canines was significantly more successful with horizontal parallax than significantly more successful with horizontal parallax than with vertical parallax. But both radiographic techniques were with vertical parallax. But both radiographic techniques were poor at localizing buccal EMC (success rate is only 63%).poor at localizing buccal EMC (success rate 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 the Film 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 through X 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, ant Maxilla & dentition, ant nasal fossa.nasal fossa.

(b) Cross Sectional(b) Cross Sectional - - Palate, Zygomatic Process Palate, Zygomatic Process of Maxilla, nasolacrimal of Maxilla, nasolacrimal Canal Nasal Septum, 2nd Canal Nasal Septum, 2nd Molar to 2nd Molar.Molar to 2nd Molar.

( c) Lateral Topographical ( c) Lateral Topographical • Half of the ridge of Half of the ridge of

Maxilla, Maxilla, Inferio Lateral aspect of Inferio Lateral aspect of the antrum, tuberosity, the antrum, tuberosity, teeth from lateral teeth 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 2 molar to 2ndnd molar.molar.

(b) Lateral cross section(b) Lateral cross sectionSoft 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 the To 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 RADIOGRAPHIC EXTRA 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 the It 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 and Used 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 the The X ray passes in a posterior anterior direction through the skull.skull.

A cassette is positioned vertically in a holding device. A grid is A cassette is positioned vertically in a holding device. A grid is used used

Head is centered in front of the cassette with the cantho meatal Head is centered in front of the cassette with the cantho meatal line.line.

UsesUses

To detect developmental abnormalities like facial asymmetries.To detect developmental abnormalities like facial 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 mediolateral Used to detect progressive change in the mediolateral

dimensions of the skull.dimensions of the skull. It offers good visualization of facial structures including frontal, It offers good visualization of facial structures including frontal,

ethmoidal sinus, nasal fossa and orbits.ethmoidal sinus, nasal fossa and orbits.


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 of anatomic 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 head 1922 – 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 the Large fixed distance from the X Ray source to the

cassette. The head of the subject is placed adjacent to a stand cassette. The head of the subject is placed adjacent to a stand holding the cassette and war immobilized with a gauge holding the cassette and war immobilized with a gauge bandage wrapped around both the face and the cassette, after bandage wrapped around both the face and the cassette, after the pt’s midsagittal plane was carefully oriented parallel to the the 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 the on proportional relationships in the face conforming to the principles used in antiquity.principles used in antiquity.www.indiandentalacademy.comwww.indiandentalacademy.com

RADIOGRAPHIC CEPHALOMETRIC RADIOGRAPHIC CEPHALOMETRIC TECHNIQUETECHNIQUE

Simplest procedure to obtain Simplest procedure to obtain head radiographs in natural head radiographs in natural head position is to instruct head position is to instruct the patients to sit upright and the patients to sit upright and look straight ahead to a point look straight ahead to a point at eye level on the wall in at eye level on the wall in front of them.front of them.

Patient is positioned within the Patient is positioned within the cephalostat using adjustable cephalostat using adjustable bilateral ear rods placed within bilateral ear rods placed within each auditory meatus, usually each auditory meatus, usually while the patient is in the while the patient is in the standing position. The midsagital standing position. The midsagital plane of the patient is vertical plane of the patient is vertical and perpendicular to the X Ray and perpendicular to the X Ray beam. It is also parallel to the film beam. It is also parallel to the film plane which in turn perpendicular plane which in turn perpendicular to the X Ray beam.to the X Ray beam.


OREINTATION IN NATURAL HEAD OREINTATION IN NATURAL HEAD POSITIONPOSITION

Orientation of pts in natural head position Orientation of pts in natural head position will result in only a small range of error. Such will result in only a small range of error. Such differences have only minor effect on the differences 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 major in 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’ sCharacterization or description comes first.Characterization or description comes first.Comparison of one individual to another is made possible Comparison 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 PlanningMore useful to make a “Cephalometric set up”More useful to make a “Cephalometric set up”


TRACING & IDENTIFICATION OF TRACING & 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 & ear Cranial 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 outcome Growth and mechano therapy contribute to the outcome of orthodontic treatment to different degrees. of orthodontic treatment to different degrees. cephalometric superimpositions demonstrate the combined cephalometric superimpositions demonstrate the combined effects of growth and mechanotherapy.effects of growth and mechanotherapy.

Regional cephalometric superimpositions are performed Regional cephalometric superimpositions are performed to evaluate three basic components of skeletal and dento to evaluate three basic components of skeletal and dento alveolar development:-maxillary ,mandibular and overall alveolar development:-maxillary ,mandibular and overall facial changes.facial changes.

Superimposition of cranial base yields information about Superimposition of cranial base yields information about the movements of facial bones away from the cranial the movements of facial bones away from the cranial structures.structures.

Superimposition of maxillary structures can be used to Superimposition of maxillary structures can be used to evaluate changes in the maxillary dento alveolar complex evaluate changes in the maxillary dento alveolar complex (PNS-ANS line).(PNS-ANS line).

Mandibular superimposition on relatively stable Mandibular superimposition on relatively stable anatomical structures can be used to evaluate dento anatomical structures can be used to evaluate dento alveolar changes.alveolar changes.


Methods of superimpositionMethods of superimposition1.Superimposition on S-N at S.1.Superimposition on S-N at S.

2.Superimposition natural reference structures such as cranial 2.Superimposition natural reference structures such as cranial base.base.

3.Using a subtraction technique where a positive copy is 3.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 place Areas of radiograph where no change has taken place appear uniformly grey.appear uniformly grey.

4.Using a “blink comparator”. Two radiographs are illuminated 4.Using a “blink comparator”. Two radiographs are illuminated alternately in rapid succession, giving an impression of alternately 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 radiographs 5.Using digital images tracings of cephalometric radiographs can be superimposed either on landmarks or structures can 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 by To identify position of unerupted canine by using lateral cephalogram, 3 different using 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 the & sagittal displacement of the incisor point of the impacted canine, angulation, length of the teeth impacted canine, angulation, length of the teeth measured on cephalogram appeared to give an measured on cephalogram appeared to give an accurate representation.accurate representation.


COMPUTERIZED CEPHCOMPUTERIZED CEPH

With introduction of digital imaging, automated and With introduction of digital imaging, automated and semi-automated landmark identification directly from the semi-automated landmark identification directly from the digital images can be done. This would avoid the digital 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 match but 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 traditional Yi Jane chen et al (AO 2000), compared the traditional and computer aided digital cephalometric landmarks and and computer aided digital cephalometric landmarks and concluded that the inter observer error for each landmark concluded that the inter observer error for each landmark in digital images was generally larger than that in the in 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 radiography Automatic computerized radiography identification of cephalometric identification of cephalometric Landmarks. Landmarks. D J Rudolph et al.D J Rudolph et al.

This study compared manual identification on a This study compared manual identification on a computer monitor and Spatial Spectrometry computer monitor and Spatial Spectrometry automatic method for landmark identification on automatic method for landmark identification on minimum resolution image. Fifteen landmarks minimum resolution image. Fifteen landmarks were selected on set of 14 test images. The were 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 between in mean landmark identification errors between manual identification on a computer display and manual identification on a computer display and automatic identification using SSautomatic identification using SS


THREE DIMENSIONAL CEPHALOMETRIC THREE 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 occur contour changes, and changes in proportion that occur with aging. Computed assisting tomographic data can be with 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 methods Precise 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 points Ability 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 reformatting CT scans were reconstructed in 3 D by reformatting

process.process.

Uses:-Uses:-

Especially useful in patient with marked dentofacial Especially useful in patient with marked dentofacial asymmetries. asymmetries.

To improve preoperative diagnostic capabilities including To improve preoperative diagnostic capabilities including volumetric analysis.volumetric analysis.


XERORADIOGRAPHYXERORADIOGRAPHY

It is the process of recording a latent radiographic It is the process of recording a latent radiographic image on aimage on a selenium coated aluminum plate ,the image is selenium coated aluminum plate ,the image is then transferred to a specially treated paper for then transferred to a specially treated paper for visualization. The whole process is fully automatic , taking visualization. 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 clearly 1) Soft tissues, bone, teeth, and air passages are clearly visible because of a large recording latitude , high visible 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 radiography Xeroradiography is superior to conventional radiography


ORTHOPANTOMOGRAPHYORTHOPANTOMOGRAPHY It is a technique for producing a single tomographic image It is a technique for producing a single tomographic image

of the facial structures that includes both the maxillary and of 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 opposite Two adjacent disks rotate at the same speed in opposite direction as an X Ray beam passes through their centers of direction 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 which It is a 3 – dimensional curved zone (focal trough) in which the structures lying with in the layer are reasonably well the 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. Patient Mid sagital plane must be centered with in the image layer. Patient ‘s chin and occlusal plane is aligned so that it is lower anteriorly, ‘s chin and occlusal plane is aligned so that it is lower anteriorly, angled 20-30 degrees below the horizontal plane. Line from the angled 20-30 degrees below the horizontal plane. Line from the tragus of the ear to the outer canthus of the eye is parallel with the tragus of the ear to the outer canthus of the eye is parallel with the floor.floor.

POSITIONING ERRORPOSITIONING ERROR

1) Pt. too far from the film. Ant teeth magnified in 1) 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 out 2) Pt. too close to the film Ant teeth narrowed and out of focus.of focus.3) Pt. Asymmetrically turned Post teeth enlarge on one 3) Pt. Asymmetrically turned Post teeth enlarge on one right or left right or left side and decreased on other side 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) horizontal Vertical (or) horizontal

to keep still throughout distortion of the part to keep still throughout distortion of the part the cycle the cycle of the image being produced of the image being produced

at the time of the movement.at the time of the movement.www.indiandentalacademy.comwww.indiandentalacademy.com

SPECIALISED IMAGING TECHNIIQUESSPECIALISED IMAGING TECHNIIQUES

Conventional tomography Conventional tomography

StereoscopyStereoscopy

ScanographyScanography

Computed tomographyComputed tomography

Magnetic resonance ImagingMagnetic resonance Imaging

UltrasonographyUltrasonography

ArthrographyArthrography

Digital radiographyDigital radiographywww.indiandentalacademy.comwww.indiandentalacademy.com

COMPUTED TOMOGRAPHYCOMPUTED TOMOGRAPHY

CT image is a display of a thin slice of the body, developed CT image is a display of a thin slice of the body, developed from multiple X ray absorption measurements made from 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 processing Digital image processing Quick and Non invasiveQuick and Non invasive


TECHNIQUESTECHNIQUES 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..

INDICATIONSINDICATIONS 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 the Control console – This allows the operator to dictate the

parameters of the CT scanparameters of the CT scan..www.indiandentalacademy.comwww.indiandentalacademy.com

IMAGE ACQUISITIONIMAGE ACQUISITION

CT images are acquired CT images are acquired in the axial, coronal, or in the axial, coronal, or sagital planes. These sagital planes. These images are taken in images are taken in succession and are succession and are generally referred to as generally referred to as slices. The information slices. The information form these multiple slices form these multiple slices can then be reformatted to can then be reformatted to produce images in other produce images in other planes.planes.


CT NUMBERS OR HOUNSFIELD CT NUMBERS OR HOUNSFIELD UNITSUNITS

The numeric data in each The numeric data in each pixel is called a CT number. pixel is called a CT number. The CT number corresponds to The CT number corresponds to the linear attenuation the linear attenuation coefficient of a particular tissue coefficient 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 = +1Muscle = +50Muscle = +50Bone = +1000Bone = +1000


Gary yip et al (seminar Gary yip et al (seminar in ortho 2004).in ortho 2004).

Concluded that micro Concluded that micro tomography is particularly tomography is particularly useful for the technically useful for the technically demanding task of assessing demanding task of assessing mineral density patterns of mineral density patterns of bone, supporting titanium bone, supporting titanium implants.implants.

The expediency, The expediency, nondestructive nature, & 3D nondestructive nature, & 3D imagery of this technique imagery of this technique used to evaluate quantity, used to evaluate quantity, quality & mechanical quality & mechanical properties of bone.properties of bone.


MAGNETIC RESONANCE IMAGING MAGNETIC 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 the MRI uses non-ionizing radiation from the radiofrequency (RF) band of the Electromagnetic radiofrequency (RF) band of the Electromagnetic spectrum.spectrum.

Unpaired Neutron/Proton Unpaired Neutron/Proton Magnetic Dipoles Magnetic Dipoles in biological tissues- H2 atom is the most in 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.MRI reflects the magnetic properties of mobile H2.www.indiandentalacademy.comwww.indiandentalacademy.com

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 state Rotation of bulk magnetic vector to pre-excitation state Induction of electric current in wire coils .Signal received and Induction of electric current in wire coils .Signal received and processed.processed.T1 T1 measures the longitudinal return of protons to align with the measures 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 to Small 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

T2 T2 measures the energy transfer between interacting protons measures the energy transfer between interacting protons after excitation. For water, CSF, saliva – Long T2 – White or after 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 sequenceApplication of RF pulses-localization of signals-Fourier Application 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 by Injected 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 diethylene DTPA-Most popular (Gaddolinium diethylene Triamine pantothenic acid).Triamine pantothenic acid).

SAFETY CONSIDERATIONSSAFETY CONSIDERATIONS

Contraindicated in pts with Ferromagnetic materials Contraindicated in pts with Ferromagnetic materials like Cardiac pacemaker.like Cardiac pacemaker.

Safety in Pregnancy not established.Safety in Pregnancy not established.


ADVANTAGESADVANTAGES It offers best resolution of tissues of low inherent It 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 in Because e at the region of the body Imaged in MRI in

controlled electronically, direct multiplannar imaging is controlled 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 hazard Relatively long imaging times and the potential hazard imposed by the presence of ferromagnetic metals in the imposed 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 when Some patients suffer from claustrophobia when

positioned in a MRI Machine.positioned in a MRI Machine.INDICATIONSINDICATIONS

It gives excellent soft tissue contrast resolution.It gives excellent soft tissue contrast resolution. Diagnosing a suspected internal derangement of the Diagnosing a suspected internal derangement of the

TMJ and evaluating the treatment of that derangement TMJ 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 mandibular Using Magnetic resonance imaging, temporo mandibular joint Effects of activator treatment are analyzed by Sabine joint Effects of activator treatment are analyzed by Sabine et al , Angle Orthodontist 6; 72, 2002 he concluded the et al , Angle Orthodontist 6; 72, 2002 he concluded the following:following:

During the one year treatment period the sagital During the one year treatment period the sagital dental arch relationship improved .On average, the dental arch relationship improved .On average, the physiologic position of disc, condyle and fossa was present physiologic position of disc, condyle and fossa was present both present and after one year activator treatment. both present and after one year activator treatment.

A pretreatment physiological disc condyle A pretreatment physiological disc condyle relationship was unaffected by activator therapy. The relationship was unaffected by activator therapy. The prevalence of sub clinical capsulitis of the inferior stratum prevalence of sub clinical capsulitis of the inferior stratum of posterior attachment during activator treatment. of posterior attachment during activator treatment.

Using magnetic resonance imaging and Using magnetic resonance imaging and cephalometric investigation , temporo mandibular joint cephalometric investigation , temporo mandibular joint remodeling in adolescent and young adults during Herbst remodeling in adolescent and young adults during Herbst treatment was analyzed by sabine et altreatment was analyzed by sabine et al

The increase in mandibular prognatism The increase in mandibular prognatism accomplished by Herbst therapy is found to be a result of accomplished by Herbst therapy is found to be a result of codylar and glenoid fossa remodeling. codylar and glenoid fossa remodeling.


ULTRASONOGRAPHYULTRASONOGRAPHY The phenomenon perceived as sound is the result of The 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 and Periodicity 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 the Electrical impulses generated by the scanner causes the

dipoles in the crystal to realign themselves and to the dipoles in the crystal to realign themselves and to the electrical field and thus suddenly change the crystal’s electrical field and thus suddenly change the crystal’s thickness. This abrupt change begins a series of vibrations thickness. This abrupt change begins a series of vibrations that produce the sound waves that are transmitted in to the that produce the sound waves that are transmitted in to the tissues being examined.tissues being examined.

ADVANTAGESADVANTAGES Does not require special facilities.Does not require special facilities. Can be used to view the joint in a continuum with out Can 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 To differentiate infantile and mature swallow. He used B +ve mode ultrasonography movements of the used B +ve mode ultrasonography movements of the tongue tip & submental musculature during swallowing tongue tip & submental musculature during swallowing were recorded on video cassette. were recorded on video cassette.

It provides a noninvasive visualization of tongue It provides a noninvasive visualization of tongue movements & no foreign body is required in the oral cavity movements & 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 elements A 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 sensitive 1) Conventional radiographic 1) a) Light sensitive Image Image elements to elements to

record record the image.the image.

b) Shades of gray to b) Shades of gray to display the Image display the Image

2) Silver halide grain 2) Light sensitive 2) Silver halide grain 2) Light sensitive elements elements

3) Randomly dispersed 3) Regular grid of rows 3) Randomly dispersed 3) Regular grid of rows and Columns and 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 grouped Sampling - 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 Pixels are arranged in proper locations and given

a a shade of gray corresponding to quantization shade of gray corresponding to quantization number. number.


ADVANTAGES OF DIGITAL RADIOLOGYADVANTAGES OF DIGITAL RADIOLOGY

Reduces time and effort needed for chemical processing Reduces 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 rough X-ray receptor in IO systems –susceptible to rough

handling.handling. Risk of system becomes obsolete.Risk of system becomes obsolete.


TECHNIQUESTECHNIQUES

Single step system Single 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 the The CCD uses a thin wafer of silicon as the

basis for image recording.basis for image recording.

Associated read out and amplifying Associated read out and amplifying electronics.electronics.

Scintillating layer-Gadolinium oxybromide or Scintillating 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 pixel Charge pocket in each pixel forms latent forms latent

imageimage

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 displayed It 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 the Electronic 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 oxide C-MOS (Complementary Metal oxide Semiconductor Semiconductor 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.www.indiandentalacademy.comwww.indiandentalacademy.com

2 STEP WIRELESS SYSTEM2 STEP WIRELESS SYSTEM

PSP plates (Phosphostimulable PSP plates (Phosphostimulable phosphor plates)phosphor plates)

COMPOSITIONCOMPOSITION

Contains “Europium – doped” Barium Contains “Europium – doped” Barium fluorohalidefluorohalideeuropium creates imperfections.europium creates imperfections.

PRINCIPLESPRINCIPLES

PHOSPHORESENCEPHOSPHORESENCE Quantified as a measure of X Quantified as a measure of X ray energy absorbed by ray energy absorbed by

material materialwww.indiandentalacademy.comwww.indiandentalacademy.com

IMAGE FORMATIONIMAGE FORMATION Radiation Radiation movement of Valance electron into Conduction movement of Valance electron into Conduction

band band migration into nearby Halogen vacancies migration into nearby Halogen vacancies (‘F’ Centers) (‘F’ Centers) Formation of Latent images.Formation of Latent images.

Stimulation by Red light Stimulation by Red light Return of electrons into the Valence Return of electrons into the Valence band band Release of energy in green spectrum Release of energy in green spectrum Fibro optics Fibro optics Photomultiplier tube Photomultiplier tube Conversion of light into Electrical Conversion of light into Electrical energy. Removal of stimulatory light by Red filter energy. 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 ADC Quantification 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.www.indiandentalacademy.comwww.indiandentalacademy.com

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 articular Ex – Asymmetries, extensive erosions changes in articular

eminance.eminance.

TRANSCRANIAL PROJECTIONTRANSCRANIAL PROJECTION

Lateral aspect of the condyle, and temporal component and Lateral 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 condylar skull base and condyles superimposed on the condylar necks and mandibular raminecks and mandibular rami

• Facial asymmetries, condylar displacement, rotation of the Facial asymmetries, condylar displacement, rotation of the mandible.mandible.

CONVENTIONAL TOMOGRAPHYCONVENTIONAL TOMOGRAPHY

• erosive changes of the condyle erosive 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 osseous Depicting true condylar position and revealing osseous

changeschanges

COMPUTED TOMOGRAPHYCOMPUTED TOMOGRAPHY

• Gives 3 dimensional shape and internal structure of the Gives 3 dimensional shape and internal structure of the osseous components of the joint and soft tissue structuresosseous components of the joint and soft tissue structures


TMJ SOFT TISSUETMJ SOFT TISSUE

ARTHROGRAPHYARTHROGRAPHY

• Information about disk position, function, morphology Information 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 effusion Inflammation and joint effusion

• MEDIAL DISK displacement are best detected.MEDIAL DISK displacement are best detected.


MAXILLARY CANINE IMPACTIONMAXILLARY CANINE IMPACTIONIn 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. www.indiandentalacademy.comwww.indiandentalacademy.com

Vertex occlusalVertex occlusal X-Ray Tube is positioned above the patient , in X-Ray Tube is positioned above the patient , in

the mid line, aiming downwards through the the mid line, aiming downwards through the vertex of the skull.vertex of the skull.

Buccal or palatal position of an unerupted teeth Buccal or palatal position of an unerupted teeth can be identified.can be identified.

Dis Adv: Radiation to eyes, gonads and Dis Adv: Radiation to eyes, gonads and pitutarygland.pitutarygland.

True lateral & PA Jaws.True lateral & PA Jaws. Steroscopic Views.Steroscopic Views.

Cross sectional spiral Cross sectional spiral tomography.tomography.


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.


Thank youThank you

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radiology in orthodontics-dr.kavitha / orthodontic courses by indian dental academy

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