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D E N TA L R A D I O G R A P H Y

R H C 4 0 6 3 R A D I O G R A P H I C P R O C E D U R E S I I I

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D E N TA L R A D I O G R A P H Y

Terminologies

Indications

Intra-oral radiography

Extra-oral radiography

Cephalometry

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TERMINOLOGIES Occlusal plane

Dental formula

Intra-oral

Extra-oral

Bitewing

Periapical

Panoramic view

OPG

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INDICATIONS Find problems in the mouth such as tooth decay, damage to the bones supporting

the teeth, and dental injuries (such as broken tooth roots). Dental X-rays are often

done to find these problems early, before any symptoms are present.

Find teeth that are not in the right place or do not break through the gum properly.

Teeth that are too crowded to break through the gums are called impacted.

Find cysts, solid growths (tumors), or abscesses.

Check for the location of permanent teeth growing in the jaw in children who still

have their primary (or baby) teeth.

Plan treatment for large or extensive cavities, root canal surgery, placement of

dental implants, and difficult tooth removals.

Plan treatment of teeth that are not lined up straight (orthodontic treatment).

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OCCLUSAL PLANE The imaginary curved surface on which upper and

lower teeth meet

Important especially when molding dentures

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DENTAL FORMULA The development of teeth and their arrangement in the mouth

The characteristic arrangement, kind, and number of teeth of human

at a given age

For adult human, the formula of teeth are as follows:

Incisors - 2/2

Canine - 1/1

Premolars - 2/2

Molars - 3/3

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I N T R A - O R A L D E N TA L X - R AY

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INTRA-ORAL Intra-oral: the film is inserted into patient's mouth

A basic rather than specialized equipment

Low power and low kilovoltage, but enough to

meet the demands of dental radiography

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INTRA-ORAL Designed so that

it will be easily

maneuvered

around patient'sface

Compact and light

Mounted on agimbal, which

allows rotation in

two planes

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INTRA-ORAL Scale are build in to

measure the angle of

rotation

Supported on a multi-jointed arm

Loose enough to be

flexed by slight pressure,

but tight enough to holdby friction

Commonly set at 65 kV,

with 10 mA

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GENERAL PROCEDURE Patient will be covered with a lead apron while sitting

upright on a chair. Thyroid shield may also be provided

Everyone else in the room wears a protective apron orstays behind a protective shield.

Patient will bite down on a small piece of cardboard or

plastic. The cardboard or plastic holds X-ray film.

Patient may have do this several times to get pictures

of all the teeth.

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BITEWING VIEW Shows the upper and lower back teeth and how the

teeth touch each other in a single view

These radiographs are used to:

check for decay between the teeth

show how well the upper and lower teeth lined up

show bone loss when severe gum disease or a

dental infection is present

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BITEWING VIEW The receptor is placed into the mouth parallel to

the crowns of the maxillary and mandibular

posterior teeth.

The patient stabilizes the receptor by biting on a

tab or bitewing holder. The horizontal angle of the

x-ray beam is then directed through the contacts of

the posterior teeth and at a 5 to 10 vertical

angle.

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PERIAPICAL VIEW Show the entire tooth, from the exposed crown to

the end of the root and the bones that support the

tooth

These radiographs are used to:

find dental problem below the gum line or in the

jaw

diagnose bone changes linked to some diseases

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PERIAPICAL VIEW A film will be placed into the mouth using a plastic film holding device

which has a metal rod with an attached ring that projects out of the mouth.

Radiographer will carefully place the film and holder into patient's mouth in

the required position to obtain a good-quality image. Patient must bitefirmly onto the film holding device to keep the film positioned properly and

ensure that it remains stable.

Radiographer must work quickly and employ techniques to minimize

discomfort as much as possible.

Once the film is positioned and stable, the cone of the x-ray unit will be

aligned, directing it toward the film and using the ring of the film holder to

help guide its position.

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OCCLUSAL VIEW Show the roof or floor of the mouth

Radiographs can be used to:

find extra teeth, teeth that have not yet broken

through the gum, jaw fractures, cleft in the cleft

palate, cyst, abscess, or growth

find any foreign objects

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OCCLUSAL VIEW The film packet, with the white surface facing downwards, is

placed centrally into the mouth, on to the occlusal surfaces of

the lower teeth, with its long axis crossways. The patient is

asked to bite together gently.

The patient then leans forwards and then tips the head

backwards as far as is comfortable, where it is supported.

The X-ray tubehead, with circular collimator fitted, is placedbelow the patients chin, in the midline, centering on an

imaginary line joining the first molars, at an angle of 90 to

the film

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TECHNIQUE ERRORS Error in technique will produce undesirable images

Notable errors are as follow:

Inadequate coverage

Backward placement

Bending

Tilted occlusal plane

Vertical alignment errors

Elongation

Foreshortening

Horizontal alignment errors

Horizontal overlapping

Centering errors

Double exposure

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INADEQUATE COVERAGE A common receptor placement error is inadequate coverage of the area to

be viewed.

This commonly occurs in molar projections when the patient cannot tolerate

proper receptor placement. Missing apices can also be caused by a receptorplacement error.

When using receptor holders, the bite block should be placed on the teeth

to be exposed and not on the opposing teeth. If the bite block is placed on

the opposing teeth and the patient is required to bite the receptor into

place, a placement error is likely to result.

Placing the receptor more lingual to the teeth where the palate and floor

are deeper will make placement easier and more comfortable for the

patient.

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BACKWARD PLACEMENT

Placing the film backwards in the mouth causes the lead foil

inside the packet to face the radiation source instead of the film.

The x-ray beam is attenuated by the lead foil before striking the

film, and embossed pattern on the foil will appear on the

processed film.

This error also results in a lighter image and confusion when

mounting the processed film.

Backwards placement is less likely with digital receptors

particularly the rigid sensors.

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BENDING Receptor bending may occur due to the curvature of the palate or lingual

arch and/or mishandled receptors

When using holders, flex the receptor into place to decrease the chances of

bending.

If the receptor is too large, bending can occur. Choose a receptor that will

adequately record the image

Bending a receptor causes the emulsion to crease, which in turn

compromises the quality of the image

Rigid digital receptors cannot be bent but phosphor plate receptors can be

creased, bent or folded. This produces a permanent artifact on the plate

and the image

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TILTED OCCLUSAL When the receptor is not placed perpendicular to the

occlusal plane, the occlusal plane will appear slanted or

diagonal.

The receptor must be placed straight or perpendicular with

the occlusal plane, or the receptor should be farther away

from the teeth to avoid this error.

Always place the biteblock in contact with the occlusal orincisal surfaces of the teeth you are imaging not on the

opposing teeth. Placement on the opposing teeth will cause

the receptor to displace when it contacts bony anatomy.

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ELONGATION Elongation or lengthening of the teeth and

surrounding structures results from

underangulation.

This error can also occur when using the bisecting

angle technique. Often the error is caused by the

x-ray beam being perpendicular to the long axis of

the teeth, rather than bisecting the angle between

the teeth and the receptor.

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FORESHORTENING Foreshortening is the result of over-angulation of the x-

ray beam.

To correct foreshortening when using the parallelingtechnique, the operator should decrease the positive

vertical angulation for maxillary projections, and

decrease the negative vertical for mandibular

projections.

This error can also occur if the receptor is not placed

parallel to the long axis of the teeth.

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HORIZONTAL OVERLAPPING

The x-ray beam should be aimed directly between

the targeted teeth in order to open interproximal

surfaces.

Horizontal alignment errors cause the image to

shift right or left, resulting in the overlapping of the

interproximal surfaces.

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CENTERING ERRORS The central ray should be aligned over the center of the receptor

with the x-ray beam directed perpendicular to the receptor.

When this alignment is not observed, a cone-cut occurs

Cone cuts appear as clear zone on traditional radiographs afterprocessing, due to the lack of x-ray exposure in the area of the

cut. When using digital imaging, the cone-cut appears as an

opaque area

The shape of the cone-cut depends on the type of collimator

used when exposing the receptor. For example, if a round

collimator or PID is used, a curved cone cut will appear

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DOUBLE EXPOSURE Double exposure results when the receptor is exposed

twice and two images appear superimposed onto each

other.

This error results in increased radiation exposure for

the patient. It is extremely important to avoid this error

because it exposes the patient to radiation twice.

To avoid this error, maintain an organized work space

in which exposed receptors are placed in one area or

turned over to separate from unexposed receptors.

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E X T R A - O R A L D E N TA L X - R AY

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EXTRA-ORAL Extra-oral: the film is outside patient's mouth

Most commonly used orthopantomography (OPG)

Offers panoramic view of patient's jaw and teeth

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EXTRA-ORAL kVp and mA can be

adjusted, as opposed

to intra-oral

equipment

Time is fixed and not

adjustable

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EXTRA-ORAL Cassette and film are

curved

The film is exposedthrough a narrow slit in

a protective metal

sheet

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EXTRA-ORAL

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EXTRA-ORAL The tube and film are

linked so that they

move in opposite

directionsimultaneously

The film moves around

the face, while the

tube moves around

the head

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EXTRA-ORAL

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EXTRA-ORAL

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PANORAMIC VIEW Show a broad view of the jaw, teeth, sinuses, nasal

area, and temporomandibular joint.

Cannot be used to find cavities

Can be used to show:

impacted teeth, bone abnormalities, cysts, solidgrowth (tumors), infections, and fractures

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C E P H A L O M E T R Y

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CEPHALOMETRY Cephalometry is the measurement of the human

head by imaging from x-ray films

Cephalometric analysis is used in dentistry, andespecially in orthodontics, to gauge the size and

spacial relationships of the teeth, jaws, and cranium.

This analysis informs treatment planning, quantifieschanges during treatment, and provides data for

clinical research.

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CEPHALOMETRY Five major components of face:

the cranium and cranial base

the skeletal maxillae

the skeletal mandible

the maxillary dentition and alveolar process

the mandibular dentition and alveolar process

These measurements will provide information to estimate the

relationships, vertically and horizontally, of the jaws to the cranial base &

to each other and the relationship of the teeth to their surrounding bone.

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