Chapter 42 Extraoral and Digital Radiography Copyright 2003, Elsevier Science (USA). All rights...

Chapter 42Extraoral and Digital

Radiography

Chapter 42Extraoral and Digital

Radiography

Copyright 2003, Elsevier Science (USA).

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Produced in the United States of America

ISBN 0-7216-9770-4

Copyright 2003, Elsevier Science (USA). All rights reserved.

IntroductionIntroduction Extraoral radiographs (outside the mouth) are taken

when large areas of the skull or jaw must be examined or when patients are unable to open their mouths for film placement.

Extraoral radiographs do not show the details as well as intraoral films.

Extraoral radiographs are very useful for evaluating large areas of the skull and jaws but are not adequate for detection of subtle changes such as the early stages of dental caries or periodontal disease.

There are many type of extraoral radiographs. Some types are used to view the entire skull, whereas other types focus on the maxilla and mandible.

Extraoral radiographs (outside the mouth) are taken when large areas of the skull or jaw must be examined or when patients are unable to open their mouths for film placement.

Extraoral radiographs do not show the details as well as intraoral films.

Extraoral radiographs are very useful for evaluating large areas of the skull and jaws but are not adequate for detection of subtle changes such as the early stages of dental caries or periodontal disease.

There are many type of extraoral radiographs. Some types are used to view the entire skull, whereas other types focus on the maxilla and mandible.


Panoramic RadiographyPanoramic Radiography Panoramic radiographs show the entire dentition

and related structures on a single film. Some types of panoramic units operate with the

patient in a seated position, and other types require the patient to be in a standing position.

Regardless of the type of machine, you must follow the manufacturer’s instructions carefully.

Because the images on a panoramic film are not as clear or as well defined as the images on intraoral films, bite-wing films are used to supplement a panoramic film to detect dental caries or periapical lesions.

Panoramic radiographs show the entire dentition and related structures on a single film.

Some types of panoramic units operate with the patient in a seated position, and other types require the patient to be in a standing position.

Regardless of the type of machine, you must follow the manufacturer’s instructions carefully.

Because the images on a panoramic film are not as clear or as well defined as the images on intraoral films, bite-wing films are used to supplement a panoramic film to detect dental caries or periapical lesions.


Basic ConceptsBasic Concepts

In panoramic radiography the film and tubehead rotate around the patient, and it produces a series of individual images.

The term panorama means “an unobstructed view of a region in any direction.” When the series of images are combined onto a single film, an overall view (panorama) of the maxilla and mandible is created.

In panoramic radiography the film and tubehead rotate around the patient, and it produces a series of individual images.

The term panorama means “an unobstructed view of a region in any direction.” When the series of images are combined onto a single film, an overall view (panorama) of the maxilla and mandible is created.


Fig 42-2 The film and x-ray tubehead move around the patient in opposite directions in panoramic radiography.Fig 42-2 The film and x-ray tubehead move around the patient in opposite directions in panoramic radiography.

Fig. 42-2Fig. 42-2


Focal TroughFocal Trough An imaginary, three-dimensional curved area

that is horseshoe shaped. This is a very important concept because

many technique errors are caused by improper positioning of the patient’s jaws within the focal trough.

When the jaws are positioned within this area, the radiograph will be clear.

When the jaws are positioned outside of this area, the images on the radiograph will appear blurred or indistinct.

An imaginary, three-dimensional curved area that is horseshoe shaped.

This is a very important concept because many technique errors are caused by improper positioning of the patient’s jaws within the focal trough.

When the jaws are positioned within this area, the radiograph will be clear.

When the jaws are positioned outside of this area, the images on the radiograph will appear blurred or indistinct.


Fig. 42-3 An example of an image layer, or “focal trough.” Fig. 42-3 An example of an image layer, or “focal trough.”

Fig. 42-3Fig. 42-3


Components of the Panoramic UnitComponents of the Panoramic Unit Panoramic x-ray tubehead

Head positioner

Exposure controls

Panoramic x-ray tubehead

Head positioner

Exposure controls


Fig. 42-4 The main components of a panoramic unit. Fig. 42-4 The main components of a panoramic unit.

Fig. 42-4Fig. 42-4


The Head PositionerThe Head Positioner Each panoramic unit has a head positioner

used to align the patient’s teeth as accurately as possible.

Each head positioner consists of a chin rest, notched bite-block, forehead rest, and lateral head supports or guides.

Each panoramic unit is different, and the operator must follow the manufacturer’s instructions on how to position the patient in the focal trough.

Each panoramic unit has a head positioner used to align the patient’s teeth as accurately as possible.

Each head positioner consists of a chin rest, notched bite-block, forehead rest, and lateral head supports or guides.

Each panoramic unit is different, and the operator must follow the manufacturer’s instructions on how to position the patient in the focal trough.


Fig. 42-5 The head positioner is used to align the patient’s teeth in the focal trough. Fig. 42-5 The head positioner is used to align the patient’s teeth in the focal trough.

Fig. 42-5Fig. 42-5


Common Errors Common Errors Patient preparation errors

• Ghost images: A ghost image looks like the real object except that it appears on the opposite side of the film.

• Lead apron artifact: If the lead apron is placed too high, or if a lead apron with a thyroid collar is used, a cone-shaped radiopaque artifact results.

Patient seating errors

• Chin too high

• Chin too low

Patient preparation errors

• Ghost images: A ghost image looks like the real object except that it appears on the opposite side of the film.

• Lead apron artifact: If the lead apron is placed too high, or if a lead apron with a thyroid collar is used, a cone-shaped radiopaque artifact results.

Patient seating errors

• Chin too high

• Chin too low


Fig. 42-13 Large hoop earrings (A) and ghost images (B). The ghost image of the earring appears on the opposite side of the film. Fig. 42-13 Large hoop earrings (A) and ghost images (B). The ghost image of the earring appears on the opposite side of the film.

Fig. 42-13Fig. 42-13


Fig. 42-14 On a panoramic radiograph, a lead apron artifact appears as a large cone-shaped radiopacity obscuring the mandible.Fig. 42-14 On a panoramic radiograph, a lead apron artifact appears as a large cone-shaped radiopacity obscuring the mandible.

Fig. 42-14Fig. 42-14


Fig. 42-16 The patient’s head is tipped too far upward. Fig. 42-16 The patient’s head is tipped too far upward.

Fig. 42-16Fig. 42-16


Fig. 42-18 The patient’s head is incorrectly positioned; the chin is tipped downward. Fig. 42-18 The patient’s head is incorrectly positioned; the chin is tipped downward.

Fig. 42-18Fig. 42-18


Positioning of the TeethPositioning of the Teeth Posterior to focal trough

• If the patient’s anterior teeth are not positioned in the groove on the bite-block and are either too far back on the bite-block or posterior to the focal trough, the anterior teeth appear “fat” and out of focus on the radiograph.

Anterior to focal trough

• If the patient’s anterior teeth are not positioned in the groove on the bite-block and are either too far forward or anterior to the focal trough, the teeth will appear “skinny” and out of focus.

Posterior to focal trough

• If the patient’s anterior teeth are not positioned in the groove on the bite-block and are either too far back on the bite-block or posterior to the focal trough, the anterior teeth appear “fat” and out of focus on the radiograph.

Anterior to focal trough

• If the patient’s anterior teeth are not positioned in the groove on the bite-block and are either too far forward or anterior to the focal trough, the teeth will appear “skinny” and out of focus.


Fig. 42-21 The patient is biting too far back on the bite-block.Fig. 42-21 The patient is biting too far back on the bite-block.

Fig. 42-21Fig. 42-21


Fig. 42-22 The anterior teeth appear widened and blurred on a panoramic film when the patient is positioned too far back on the bite-block.Fig. 42-22 The anterior teeth appear widened and blurred on a panoramic film when the patient is positioned too far back on the bite-block.

Fig. 42-22Fig. 42-22


Fig. 42-23 The anterior teeth appear narrowed and blurred on a panoramic film when the patient is positioned too far forward on the bite-block.Fig. 42-23 The anterior teeth appear narrowed and blurred on a panoramic film when the patient is positioned too far forward on the bite-block.

Fig. 42-23Fig. 42-23


Fig. 42-24 If the patient is not standing erect, superimposition of the cervical spine (arrows) may be seen on the center of the panoramic film.Fig. 42-24 If the patient is not standing erect, superimposition of the cervical spine (arrows) may be seen on the center of the panoramic film.

Fig. 42-24Fig. 42-24


Positioning of the SpinePositioning of the Spine If the patient’s spine is not straight, the

cervical spine will appear as a radiopaque artifact in the center of the film and obscure diagnostic information.

If the patient’s spine is not straight, the cervical spine will appear as a radiopaque artifact in the center of the film and obscure diagnostic information.


Extraoral RadiographyExtraoral Radiography Extraoral radiographs provide images of larger areas

such as the skull and jaws. In some instances, an extraoral film may be

necessary for handicapped patients who cannot open their mouths for film placement, or because a patient has swelling or severe pain and is unable to tolerate the placement of intraoral films.

Extraoral films are also very useful for patients who are uncooperative and may refuse to open their mouths.

Images seen on an extraoral film are not as clear or as well defined as the images seen on an intraoral radiograph.

Extraoral radiographs provide images of larger areas such as the skull and jaws.

In some instances, an extraoral film may be necessary for handicapped patients who cannot open their mouths for film placement, or because a patient has swelling or severe pain and is unable to tolerate the placement of intraoral films.

Extraoral films are also very useful for patients who are uncooperative and may refuse to open their mouths.

Images seen on an extraoral film are not as clear or as well defined as the images seen on an intraoral radiograph.


EquipmentEquipment Extraoral radiographs may be taken with a

standard intraoral x-ray machine. To aid in patient positioning, special head

positioning and beam alignment devices can be added to the standard x-ray unit.

In addition, panoramic x-ray units may also be fitted with a special device known as a cephalostat.

The cephalostat includes a film holder and head positioner that allow the operator to easily position the patient.

Extraoral radiographs may be taken with a standard intraoral x-ray machine.

To aid in patient positioning, special head positioning and beam alignment devices can be added to the standard x-ray unit.

In addition, panoramic x-ray units may also be fitted with a special device known as a cephalostat.

The cephalostat includes a film holder and head positioner that allow the operator to easily position the patient.


Grid Grid

A device used to decrease film fog and increase the contrast of the radiographic image.

It does this by reducing the amount of scatter radiation that reaches an extraoral film during exposure.

Scatter radiation causes film fog and reduces film contrast.

A device used to decrease film fog and increase the contrast of the radiographic image.

It does this by reducing the amount of scatter radiation that reaches an extraoral film during exposure.

Scatter radiation causes film fog and reduces film contrast.


Fig. 42-27 A grid decreases the amount of scatter radiation that reaches the extraoral film. Fig. 42-27 A grid decreases the amount of scatter radiation that reaches the extraoral film.

Fig. 42-27Fig. 42-27


Lateral Jaw ProjectionLateral Jaw Projection Used to view the posterior region of the

mandible. This type of projection is very useful for patients with a limited jaw opening and in patients who cannot or will not tolerate intraoral film placement.

A lateral jaw projection does not provide as much diagnostic information as a panoramic radiograph.

The advantage is that the lateral jaw projection can be taken with a standard x-ray unit.

Used to view the posterior region of the mandible. This type of projection is very useful for patients with a limited jaw opening and in patients who cannot or will not tolerate intraoral film placement.

A lateral jaw projection does not provide as much diagnostic information as a panoramic radiograph.

The advantage is that the lateral jaw projection can be taken with a standard x-ray unit.


Lateral Jaw Projection Techniques Lateral Jaw Projection Techniques Body of mandible projection

Ramus of mandible projection

Body of mandible projection

Ramus of mandible projection


Fig. 42-28 A, The body of the mandible; proper patient and film positioning is shown as viewed from the front and side of the patient. B, The body of the mandible.Fig. 42-28 A, The body of the mandible; proper patient and film positioning is shown as viewed from the front and side of the patient. B, The body of the mandible.

Fig. 42-28Fig. 42-28


Ramus of the MandibleRamus of the Mandible This film is used to evaluate impacted third

molars, large lesions, and fractures that extend into the ramus of the mandible.

The ramus from the angle of the mandible to the condyle is visible in this projection.

This film is used to evaluate impacted third molars, large lesions, and fractures that extend into the ramus of the mandible.

The ramus from the angle of the mandible to the condyle is visible in this projection.


Fig. 42-29 A, Ramus of the mandible; proper patient and film positioning is shown as viewed from the front and side of the patient. B, An example of a lateral jaw radiograph; the ramus of the mandible.

Fig. 42-29 A, Ramus of the mandible; proper patient and film positioning is shown as viewed from the front and side of the patient. B, An example of a lateral jaw radiograph; the ramus of the mandible.

Fig. 42-29Fig. 42-29


Skull Radiography Skull Radiography Lateral cephalometric projection

Posteroanterior projection

Water’s projection

Submentovertex projection

Reverse Towne’s projection

Lateral cephalometric projection

Posteroanterior projection

Water’s projection

Submentovertex projection

Reverse Towne’s projection


Fig. 42-30 B, An example of a lateral cephalometric radiograph.Fig. 42-30 B, An example of a lateral cephalometric radiograph.

Fig. 42-30 BFig. 42-30 B


Fig. 42-31 B, An example of a posteroanterior skull radiograph.Fig. 42-31 B, An example of a posteroanterior skull radiograph.

Fig. 42-31 BFig. 42-31 B


Fig. 42-33 B, An example of a submentovertex radiograph. Fig. 42-33 B, An example of a submentovertex radiograph.

Fig. 42-33 BFig. 42-33 B


Fig. 42-34 B, An example of a reverse Towne’s radiograph.Fig. 42-34 B, An example of a reverse Towne’s radiograph.

Fig. 42-34 BFig. 42-34 B


Temporomandibular Joint Radiography Temporomandibular Joint Radiography Radiographs of the temporomandibular joint

(TMJ) can be very difficult to examine because of the multiple adjacent bony structures.

The articular disc and other soft tissues of the TMJ cannot be examined by radiographs.

Special imaging techniques (e.g., arthrography, magnetic resonance imaging) must be used.

Radiographic projections of the TMJ can be used to show the bone and the relationship of the jaw joint.

Radiographs of the temporomandibular joint (TMJ) can be very difficult to examine because of the multiple adjacent bony structures.

The articular disc and other soft tissues of the TMJ cannot be examined by radiographs.

Special imaging techniques (e.g., arthrography, magnetic resonance imaging) must be used.

Radiographic projections of the TMJ can be used to show the bone and the relationship of the jaw joint.


Fig. 42-36 Patient positioned for a transcranial radiograph of the temporomandibular joint.Fig. 42-36 Patient positioned for a transcranial radiograph of the temporomandibular joint.

Fig. 42-36Fig. 42-36


Digital RadiographyDigital Radiography Advances in digital technology have led to a

unique “filmless” imaging system known as digital radiography.

Introduced in 1987, digital radiography has influenced both how dental disease is recognized and how it is diagnosed.

In the last 2 years, the use of digital radiography is rapidly increasing in both general and specialty dental practices.

Numerous companies are producing digital radiography systems.

Advances in digital technology have led to a unique “filmless” imaging system known as digital radiography.

Introduced in 1987, digital radiography has influenced both how dental disease is recognized and how it is diagnosed.

In the last 2 years, the use of digital radiography is rapidly increasing in both general and specialty dental practices.

Numerous companies are producing digital radiography systems.


The Basics of Digital RadiographyThe Basics of Digital Radiography Digital radiography uses a sensor to capture

a radiographic image, breaking it into electronic pieces and storing the image in a computer.

The patient is exposed to less x-radiation than with conventional radiography.

The image is displayed on a computer screen rather than on film.

The term image (not radiograph) is used to describe the pictures that are produced.

Digital radiography uses a sensor to capture a radiographic image, breaking it into electronic pieces and storing the image in a computer.

The patient is exposed to less x-radiation than with conventional radiography.

The image is displayed on a computer screen rather than on film.

The term image (not radiograph) is used to describe the pictures that are produced.


The x-ray beam strikes the sensor.

An electronic charge is produced on the surface of the sensor, and this electronic signal is digitized.

The digital sensor in turn transmits this information to the computer.

Software in the computer is used to store the image electronically.

The x-ray beam strikes the sensor.

An electronic charge is produced on the surface of the sensor, and this electronic signal is digitized.

The digital sensor in turn transmits this information to the computer.

Software in the computer is used to store the image electronically.

The Basics of Digital Radiography cont’dThe Basics of Digital Radiography cont’d


Fig. 42-38 The size of the electronic sensor is compared with sizes 0, 1, and 2 of traditional intraoral film. Fig. 42-38 The size of the electronic sensor is compared with sizes 0, 1, and 2 of traditional intraoral film.

Fig. 42-38Fig. 42-38


Fig. 42-39 All types of radiographs may be produced in digital format.Fig. 42-39 All types of radiographs may be produced in digital format.

Fig. 42-39Fig. 42-39


Radiation ExposureRadiation Exposure Digital radiography requires much less x-

radiation than conventional radiography because the sensor is more sensitive to x-rays than to conventional film.

Exposure times for digital radiography are 50% to 80% less than that required for radiography using conventional film.

With less radiation, the absorbed dose to the patient is significantly lower.

Digital radiography requires much less x-radiation than conventional radiography because the sensor is more sensitive to x-rays than to conventional film.

Exposure times for digital radiography are 50% to 80% less than that required for radiography using conventional film.

With less radiation, the absorbed dose to the patient is significantly lower.


Equipment Equipment For digital radiography, special equipment is

required. The essential components include:

• Dental x-ray unit

• Intraoral sensor

• Computer

For digital radiography, special equipment is required. The essential components include:

• Dental x-ray unit

• Intraoral sensor

• Computer


Types of Digital Imaging Types of Digital Imaging

Direct digital imaging

Indirect digital imaging

Storage phosphor imaging

The difference between each method is in how the image is obtained and in what size the receptor plates are available (e.g., panoramic).

Direct digital imaging

Indirect digital imaging

Storage phosphor imaging

The difference between each method is in how the image is obtained and in what size the receptor plates are available (e.g., panoramic).


Fig. 42-40 Computer with modified image.Fig. 42-40 Computer with modified image.

Fig. 42-40Fig. 42-40


Fig. 42-15: If the tongue is not placed on the roof of the mouth, a radiolucent shadow will be superimposed over the apices of the maxillary teeth. Fig. 42-15: If the tongue is not placed on the roof of the mouth, a radiolucent shadow will be superimposed over the apices of the maxillary teeth.

Fig. 42-15Fig. 42-15

Chapter 42 Extraoral and Digital Radiography Copyright 2003, Elsevier Science (USA). All rights...

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