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RADIOGRAPHY DENTALELLE TUTORING DENTALELLE TUTORING - WWW.DENTALELLE.COM 1

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DENTALELLE TUTORING - WWW.DENTALELLE.COM 1

RADIOGRAPHYDENTALELLE TUTORING

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HISTORY

In 1895, Wilhelm Konrad Roentgen was searching for invisible light by experimenting with a Crookes vacuum discharge tube. This is a glass tube in which the vacuum is nearly complete, having a negative electrode (cathode) and a positive electrode (anode). Many investigators believed that invisible light rays were emitted from the negative electrode when a high voltage current was sent through the tube. With the room darkened and the tube covered with black paper,

Roentgen passed a high voltage current through the Crookes tube and was surprised to observe that a fluorescent screen lying on a table at some distance was glowing brightly. He then noted that a shadow was produced when an object was placed between the tube and the screen. Further experimentation revealed that the rays that caused the fluorescent screen to glow also acted upon the emulsion on photographic plates in the same manner as light. Thus it was shown that the rays produced would pass through some substances through which light would not pass. In later years scientists have referred to them as Roentgen rays.

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SOURCES OF RADIATION

Natural Background Radiation. There are three sources of natural background radiation: cosmic, earth, and internal. Although

natural background radiation may be harmful, man has lived in this environment without significant injurious effects since his appearance on earth.

Man-Made Radiation. Man-made radiation has many sources. Some of them are from medical and dental radiographs,

occupational exposure, fallout from weapons testing, television sets, and certain radioactive watch dials, clocks, and meters. Man-made radiation, used improperly, can be significantly more harmful to man than natural background.

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TYPES OF RADIATION

Particulate. Particulate or corpuscular radiation comes from radioactive decay or disintegration of radioactive

materials.

Alpha and beta particles are examples of this type radiation.

Electromagnetic. Electromagnetic radiation covers a very wide spectrum ranging from electrical power to visible light

to x and gamma rays.

X-rays are electromagnetic

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THE X-RAY MACHINE

The Control Panel. The components of the control panel are switches, dials, gauges, and

lights. Basically, each control panel has the same function, the arrangement and location of these components will differ, depending upon the make, model, and year of construction of the dental x-ray unit. An operator's manual is issued with each unit. The operator should study it until he is familiar with its operational capability.

The Extension Arm. The tube head is attached to the metal extension arm by means of a

yoke that can revolve 360 degrees horizontally where it is connected. The construction of the yoke also provides vertical movement as well.

The Tube Head Inside the metal tube housing is the x-ray tube. This tube emits

radiation in the form of photons or x-rays. X-ray photons expose the film. In addition to exposing the film, it also exposes the patient to radiation.

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STEPS

The First Step When the unit is turned on, the filament of the cathode is heated by electrical current, causing it to

emit electrons

The Second Step

The electrons or electron cloud from the filament are drawn across the opening toward the anode. The anode is made of tungsten and is sometimes called the tungsten target.

The Third Step

Collison of electrons with the anode (tungsten target). This rapid deceleration of electrons produces x-rays, also referred to as photons.

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HOW IT WORKS

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PROTECTION

The filter and collimator (diaphragm) block the majority of the unwanted x-ray photons.

Filter The aluminum filter or disk is placed in the path of the x-ray beam. It is located at the base of the

cone or position indicating device (PID) just inside the metal housing. The filter completely covers the opening where the x-ray beam emerges from the x-ray tube. The reason for the aluminum filter is to absorb the low energy, long wavelength x-rays (photons) and allow the high energy, short wavelength x-rays (photons) to pass through the filter. Filters on dental x-ray machines with over 70 kVp have a minimum thickness of 2.5 mm of aluminum. Those machines below 70 kVp have a safety standard minimum of 1.5 mm aluminum.

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COLLIMATION

The lead diaphragm is collocated with the aluminum filter. It restricts the x-ray beam to the desired size.

The diaphragm or collimator is constructed of 1/16-inch lead. Without this collimator, x-ray photons would cover a wide area of the patient's head.

With the lead diaphragm or collimator in place, only the area necessary for exposure receives the primary beam.

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COLLIMATION AND FILTER

Collimator

Filter

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RADIATION MONITORING

It requires all primary x-ray technicians to wear a dosimeter or film badge. The dosimeter monitors or measures radiation received by the technician. Radiation standards for the technician operating a dental x-ray machine, the level of radiation must not ever exceed an accumulated whole body dose, in rems, of five times the number of years beyond age 18 and a maximum of three rems in any 3-month period.

NOTE: The term rem refers to "roentgen equivalent in man," a unit measuring the biological effect of radiation energy. For x-rays, 1 rem is equal to 1 rad, or "radiation absorbed dose" (rad).

Standards for dental x-ray booths or rooms require a shielding thickness of 1/16-inch lead or equivalent. The timer switch used to activate the machine for exposures is permanently affixed to the outside wall. The timer switch is mounted outside the protective shielding to prevent the operator from standing inside the booth during exposures.

The shield is so designed that the radiation must scatter at least twice before reaching the x-ray technician. Leaded glass on the booth or shield provides a continuous view of the patient during the exposure. Consequently, any holding of the film or tube head by the x-ray technician is strictly prohibited.

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QUALITY AND QUANTITY

The quality (kVp) of the x-ray beam is controlled by the voltage, while the milliamperes control the quantity. An increase in the voltage and milliamperes reduces exposure time for the patient.

X-ray Beam Quality Voltage provides contrast to the film. The desired contrast appears as various shades of gray, black and white.

Increased voltage provides less contrast (or more shades of gray). However, the beam has more penetrating power. Decreased voltage, on the other hand, provides more contrast (fewer shades of gray and more black and white shades). However, there is less penetrating power in the low voltage exposure.

X-ray Beam Quantity The more x-rays (photons) in the x-ray beam, the more dense (dark) the x-ray negative (radiograph) becomes. By

increasing the milliamperes, we increase the number of available electrons at the cathode filament. When they impact on the anode (tungsten target), a greater number of x-rays (photons) are also produced. The more x-rays that are available to penetrate an object, the more dense (dark) is the x-ray negative (radiograph).

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PHOTONS

X-ray photons are electromagnetic rays produced in the x-ray tube head when electrons from the cathode filament strike the anode target. They are bundles of pure energy. The photons transfer their energy to the substance through which they pass whether it be air, an x-ray film, or the living tissue of the patient or the specialist.

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PHOTONS AND ATOMS

Photon collision with the nucleus of an atom.

The photon may strike the nucleus of an atom. If this occurs, the atom will be destroyed and the photon will release or expend its energy.

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DIRECT PHOTON

A direct photon hit upon an electron by a photon. The photon may strike an electron with a direct hit. This action will result in the release of the photon's energy, transferring its energy to the electron.

The electron will be dislodged from its shell.

When an electron is dislodged in this manner, it is called a photo-electron. The dislodged or departing electron (now a photo-electron) will have energy to ionize or strike other electrons.

This is a form of scattered/secondary radiation

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INDIRECT PHOTON HIT

The photon may strike one of the orbiting electrons with a glancing blow, dislodging the electron from its shell.

By striking a glancing blow, the photon will still possess energy and go on to strike other electrons.

The dislodged electron becomes a photon-electron and will have energy itself. It, too, may strike and dislodge other electrons.

This is also a form of scattered/secondary radiation.

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HARMFUL EFFECTS TO KNOW

Somatic Effects.

(1) Erythema. This is the reddening of the skin much like that of a sunburn; however, radiation exposure affects deeper tissue.

(2) Radiodermatitis. This refers to dry, flaky skin that doesn't heal easily. Ulcerations may become malignant.

(3) Cataracts. An overexposure to the eye could result in cataracts (a clouding of the lens or of its surrounding transparent membrane); however, this effect will appear long after the original exposure.

(4) Cancer. The cause of most natural occurring cancers is unknown. With increased exposure to radiation there is an increase in the incidence of cancer.

(5) Alopecia (epilation). This is hair loss.

Genetic Effects.

(1) Female. The ovaries are especially sensitive to radiation to the female fetus before birth and through childhood. The ovaries decline in sensitivity when the female reaches 20 to 30 years of age. After this time, there is increased sensitivity with increasing age.

(2) Male.

(3) An unborn child. The period of greatest danger is between 18 and 45 days of gestation. The results of excessive exposure could result in reduced growth, skeletal malformation, vision problems, and reduced head size which is associated with mental retardation.

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TYPES OF FILMS

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BITEWINGS

Bitewing images focus on the clinical crowns of both the maxillary and mandibular teeth. Bitewings do not show the apices of the tooth and cannot be used to diagnose in this area.

The greatest value of bitewing radiographic images is the detection of interproximal caries in the early stages of development, before it is clinically apparent.

Bitewing images also reveal the size of the pulp chamber and the relative extent to which proximal caries have penetrated.

Bitewings also provide a useful adjunct to evaluating periodontal conditions.

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PERIAPICALS

The purpose of the intraoral periapical examination is to obtain a view of the entire tooth and its surrounding structures

Two exposure techniques may be employed for periapical radiography: the paralleling technique and the bisecting angle technique. The paralleling technique is the preferred method. This technique provides less image distortion and reduces excess radiation to the patient. The paralleling technique should always be attempted before other techniques.

The bisecting technique can be employed for patients unable to accommodate the positioning of the paralleling technique. Disadvantages to the bisecting technique include image distortion and excess radiation due to increased angulations involving the eye and thyroid glands.

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OCCLUSAL

Occlusal radiography is a supplementary radiographic examination designed to provide a more extensive view of the maxilla and mandible.

The occlusal image is very useful in determining the buccolingual extension of pathologic conditions, and provides additional information as to the extent and displacement of fractures of the mandible and maxilla. Occlusal radiographic images also aid in localizing unerupted teeth, retained roots, foreign bodies, and calculi in the submandibular and sublingual salivary glands and ducts.

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FULL MOUTH SERIES – 18 FILMS OR 22 FILMS

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EDENTULOUS

Placement of the radiographic receptor holding device may be complicated by its tendency to tip or slip into the voids which would normally be occupied by the crowns of the missing teeth. This can usually be overcome by placing cotton rolls between the patient’s alveolar ridge and the holder, thereby supporting it in position.

The use of radiographic receptor holders allows the paralleling technique to be used with edentulous patients. The operator may be able to reduce radiation exposure in the edentulous patient by 25 % by using the paralleling technique. The radiographic receptor can be held in biteblocks to which cotton rolls have been taped. To prevent patient discomfort on biting due to missing teeth and resultant over-closing of the arches, the cotton rolls can be attached to the upper and lower surfaces of the biteblocks. Opposing arch denture or partial denture appliances can be left in place to make contact with the biteblock.

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ANGULATION

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PARALLELING

The paralleling technique of intraoral radiography was developed by Gordon M. Fitzgerald and its basis lies in the principle that image sharpness is primarily affected by focal-receptor distance (distance from the focal spot within the tube head and the receptor), object receptor distance, motion, and the effective size of the focal spot of the tube.

Successfully using the paralleling technique depends largely on maintaining certain essential conditions: 1) the receptor should be flat;

2) the receptor must be positioned parallel to the long axis of the teeth; and

3) the central ray of the radiographic beam must be kept perpendicular to the teeth and receptor.

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DETAILS

To achieve parallelism between the receptor and tooth (i.e., to avoid bending or angling the receptor) there must be space between the object and receptor. However, remember that as the object-to-receptor distance increases, the image magnification or distortion also increases. The goal is to have the focal spot at least 12” or 30 cm from the receptor to reduce image distortion.

The anatomic configuration of the oral cavity determines the distance needed between receptor and tooth and varies among individuals. A diagnostic quality image can be obtained provided that the receptor is not more than 20 degrees out of parallel with the tooth, and that the face of the PID/cone is exactly parallel to the receptor to produce a central beam which is perpendicular to the long axis of the tooth and the receptor.

The major advantage of the paralleling technique, when done correctly, is that the image formed on the receptor will have both linear and dimensional accuracy. The major disadvantages are the difficulty in placing the receptor and the relative discomfort the patient must endure as a result of the receptor holding devices used to maintain parallelism.

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ANGULATION

The position of the tube head is usually adjusted in two directions:  vertically and horizontally. 

The vertical plane is adjusted by moving the tube head up and down.  The horizontal plane is adjusted by moving the tube head from side to side.  By convention, deflecting the head so that it points downward is described as positive vertical angulation or + vertical. 

Correspondingly, an upward deflection is referred to as negative vertical angulation or – vertical.  The degree of vertical angulation is usually described in terms of plus or minus degrees as measured by a dial on the side of the tube head

The tooth, the receptor, and end of the position indicating device (PID) are all kept on parallel planes. If the vertical angulation is excessive, the image will appear foreshortened. Insufficient vertical angulation produces an elongated image.

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CONTINUED

The beam’s horizontal direction determines the degree of overlap among the tooth images at the interproximal spaces. When radiographing relatively aligned teeth, if the central beam is not perpendicular to the interproximal spaces, the teeth will overlap and the spaces between the contacts will close on the image.

The degree of overlapping will increase or decrease as the beam angle increases or decreases from perpendicular.

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HOLDERS

Rinn Holders for Paralleling technique

Snap-A-Ray for Bisecting

Stabe Bite Blocks for Bisecting

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REMEMBER

When taking a full mouth survey, the radiographer should always attempt to follow the same exposure sequence.

Since patients tolerate anterior images better, they should be done first. Starting with the maxillary central incisors and proceeding distally, first along one side, then the other, is recommended.

The radiographic parameters or exposure factors should also be determined prior to placing receptors in the patient’s mouth.

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HOW-TO

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MAXILLARY ANTERIORS

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STEPS FOR MAXILLARY ANTERIORS

Center the receptor on the central/lateral incisors.

Position the receptor in the palate as posteriorly as possible so that the entire tooth length will appear on the radiographic image, with approximately a one-eighth inch border on the receptor extending below the incisal edge of the teeth. Position the biteblock on the incisal edges of the teeth to be radiographed

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible without actually touching the patient. Align the tube head close to the aiming ring, and center

Expose the radiograph

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MAXILLARY CANINES

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MAXILLARY CANINES

Center the receptor on the canine and first premolar. Position the receptor in the palate as posteriorly as possible so that the entire tooth length will appear on the radiographic image with approximately a one-eighth inch border below the incisal edge of the canine.

Position the biteblock on the incisal edges of the teeth to be radiographed.

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible. Align the tube head close to the aiming ring, and center

Expose

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MAXILLARY PREMOLARS

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MAXILLARY PREMOLARS

Center the receptor on the premolars . The receptor should be parallel with the long axis of the tooth. Position the receptor in the palate so that the entire tooth length will appear on the radiographic image with approximately a one-eighth inch border below the cuspal ridge.

Align the anterior edge of the receptor with the canine so that the image captured on the anterior border of the receptor will include the distal third of the canine. Position the biteblock on the occlusal surfaces of the teeth to be radiographed.

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. (The occlusal border of the receptor tends to slip lingually.)

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible without actually touching the patient. Align the tube head close to the aiming ring, and center

Expose

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MAXILLARY MOLAR

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MAXILLARY MOLARS Center the receptor on the molars. The receptor should be parallel with the long axis of

the tooth.

Position the receptor in the palate so that the entire tooth length will appear on the radiographic image with approximately a one-eighth inch border below the cuspal ridge. Align the anterior border of the receptor with the second premolar so that the image captured on the anterior edge of the receptor will be the distal third of the second premolar. Position the biteblock on the occlusal surfaces of the teeth to be radiographed.

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position.

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible without actually touching the patient. Align the tube head close to the aiming ring, and center

Expose

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MANDIBULAR ANTERIORS

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MANDIBULAR ANTERIORS Center the receptor on the mandibular central and lateral incisors. It may be necessary to

displace the tongue distally and depress the receptor onto the floor of the mouth so that the entire tooth length will show with approximately a one-eighth inch border above the incisal edges.

The receptor must be as posterior as the anatomy allows and the biteblock should be positioned on the edges of the incisors to be radiographed.

A cotton roll may be inserted between the maxillary teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be adjusted as the patient closes and the floor of the mouth relaxes.

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible without actually touching the patient. Align the tube head close to the aiming ring, and center

Expose

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MANDIBULAR CANINES

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MANDIBULAR CANINES

Center the receptor on the mandibular canine. It may be necessary to displace the tongue distally and depress the receptor onto the floor of the mouth so that the entire tooth length will show with approximately a one-eighth inch border above the cuspal edge. The receptor must be as posterior as the anatomy allows and the biteblock should be positioned on the edges of the teeth to be radiographed.

A cotton roll may be inserted between the maxillary teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be adjusted as the patient closes and the floor of the mouth relaxes.

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible without actually touching the patient. Align the tube head close to the aiming ring, and center

Expose

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MANDIBULAR PREMOLARS

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MANDIBULAR PREMOLARS

Center the receptor on the premolars. The receptor should be parallel with the long axis of the tooth. The object-to-receptor distance in both the mandibular premolar and molar regions is minimal since the oral anatomy only allows the receptor to be positioned very close to the teeth and still remain parallel.

Align the anterior border of the receptor with the canine so that the image captured on the anterior edge of the receptor will be the distal third of the canine. Position the biteblock on the occlusal surfaces of the teeth to be radiographed.

A cotton roll may be inserted between the maxillary teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be adjusted as the patient closes and the floor of the mouth relaxes.

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible without actually touching the patient. Align the tube head close to the aiming ring, and center

Expose

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MANDIBULAR MOLARS

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MANDIBULAR MOLARS

Center the receptor on the molars. The receptor should be parallel with the long axis of the tooth. Depress the receptor onto the floor of the mouth so the entire length of the teeth will appear with approximately a one-eighth inch border above the occlusal surface.

Align the anterior border of the receptor with the second premolar so that the image captured on the anterior edge of the receptor will be the distal third of the second premolar. Position the biteblock on the occlusal surfaces of the mandibular teeth.

A cotton roll may be inserted between the maxillary teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be adjusted as the patient closes and the floor of the mouth relaxes.

Slide the aiming ring down the indicator rod; it should be as close to the skin as possible without actually touching the patient. Align the tube head close to the aiming ring, and center

Expose

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BISECTING TECHNIQUE

The dotted line BD bisects the triangle, dividing it exactly in half. Thus, two equal triangles are formed from the original. Legs AB and BC were unchanged and thus are still equal.

The original line CA was divided in half by D, and thus the lines AD and CD are equal.

We know that the angle at point B was 60 degrees, and since it was bisected (divided equally), it now is 30 degrees at the intersections of AD and BD.

We also know that bisecting the angle did not affect the angle at the old point A which was 60 degrees, and still is.

The angle at the bisecting point DC must be 90 degrees because the sum of all the angles in any triangle is 180 degrees, and thus 180-(60+30)=90.

Cyzynski’s Rule of Isometry states that two triangles are equal when they share one complete side, and have two equal angles. We can see that triangles ADB and BDC share the common side BD.

We know further that the angles ADB and BDC are equal because D was defined as a bisector of the old angle ABC.

Lastly, we know that the angles CAB and BCA were unchanged by bisecting and are still equal. Therefore, under Cyzynski’s theorem, we can prove the triangles ABD and CBD are equal.

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BISECTING

• Horizontal angulation: The horizontal angulation of the tube head should be adjusted for each projection to position the central ray through the contacts in the region to be examined.

• Vertical angulation: The operator should position the central ray of the x-ray beam so that it is perpendicular to the imaginary line bisecting the angle formed between the tooth long axis and the receptor. This principle works well with flat, two dimensional structures. If the vertical angulation is excessive the image will appear foreshortened. Insufficient vertical angulation produces an elongated image.

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BEAM ANGULATION

Projection Maxilla MandibleIncisors +40 degrees -15 degreesCanine +45 degrees -20 degrees

Premolar +30 degrees -10 degreesMolar +20 degrees -5 degrees

A MUST know for the exam (and a handy chart for the real world

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POSITIONING

Maxillary region: For bisecting angle radiographic images of the maxilla, the patient should be positioned so that the maxillary occlusal plane is parallel to the floor and the sagittal plane of the patient’s head is perpendicular to the floor.

Mandibular region: For bisecting angle radiographic images of the mandible, the patient should be positioned so that the mandibular occlusal plane is parallel to the floor and the sagittal plane of the patient’s head is perpendicular to the floor.

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ANGULATION FOR THE BISECTING

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MAXILLARY ANTERIORS

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MAXILLARY ANTERIORS

Center the receptor on the central/lateral incisors as close as possible to the lingual surfaces of the teeth with approximately a one-eighth inch border of the receptor extending below the incisal edge of the teeth Position the biteblock on the incisal edges of the teeth to be radiographed

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position.

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should bisect the central/lateral. For maxillary exposures the tube head will be pointed down for positive (+) angulation.

Expose

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MAXILLARY CANINES

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MAXILLARY CANINES

Center the receptor on the canine as close as possible to the lingual surfaces of the teeth with approximately a one-eighth inch border of the receptor extending below the incisal edge of the. Position the biteblock on the incisal edges of the teeth to be radiographed

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position.

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should bisect the canine. For maxillary exposures the tube head will be pointed down for positive (+) angulation.

Expose

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MAXILLARY PREMOLARS

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MAXILLARY PREMOLARS

Center the receptor on the premolars as close as possible to the lingual surfaces of the teeth. Position the receptor in the palate so that the entire tooth length will appear on the radiographic image with approximately a one-eighth inch border below the cuspal ridge.

Align the anterior border of the receptor with the canine so that the image captured on the anterior edge of the receptor will be the distal third of the canine. Position the biteblock on the occlusal surface of the teeth being radiographed

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. (Watch the occlusal border of the receptor; it tends to slip down anteriorly.)

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should pass between the contact of the first and second premolar. For maxillary exposures the tube head will be pointed down for positive (+) angulation.

Expose

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MAXILLARY MOLARS

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MAXILLARY MOLARS

Center the receptor on the molars as close as possible to the lingual surfaces of the teeth. Position the receptor in the palate so that the entire tooth length will appear on the radiographic image with approximately an one-eighth inch border below the cuspal ridge.

Align the anterior border of the receptor with the second premolar so that the image captured on the anterior edge of the radiographic image is the distal third of the second premolar. Position the biteblock on the occlusal surface of the teeth being radiographed.

A cotton roll may be inserted between the mandibular teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position.

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should pass between the contact of the first and second molar (Figure 51). For maxillary exposures the tube head will be pointed down for positive (+) angulation.

Expose

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MANDIBULAR ANTERIORS

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MANDIBULAR ANTERIORS

Center the receptor on the central/lateral incisors as close as possible to the lingual surfaces of the teeth with approximately a one-eighth inch border of the receptor extending above the incisal edge of the teeth.  Position the biteblock on the incisal edges of the teeth to be radiographed.

A cotton roll may be inserted between the maxillary incisors and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be straightened as the patient closes and the floor of the mouth relaxes.

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should pass between the central/lateral incisors. For mandibular exposures the tube head will be pointed up for negative (-) angulation.

Expose

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MANDIBULAR CANINES

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MANDIBULAR CANINES

Center the receptor on the canine as close as possible to the lingual surfaces of the teeth with approximately a one-eighth inch border of the receptor extending above the incisal edge of the canine. Position the biteblock on the incisal edges of the teeth to be radiographed.

A cotton roll may be inserted between the maxillary teeth and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be straightened as the patient closes and the floor of the mouth relaxes.

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should bisect the canine. For mandibular exposures the tube head will be pointed up for negative (-) angulation.

Expose

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MANDIBULAR PREMOLARS

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MANDIBULAR PREMOLARS

Center the receptor on the premolars as close as possible to the lingual surfaces of the teeth. Align the anterior border of the receptor with the canine so that the image captured on the anterior edge of the receptor will be the distal third of the canine. Position the biteblock on the occlusal surface of the teeth to be radiographed.

A cotton roll may be inserted between the maxillary premolars and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be straightened as the patient closes and the floor of the mouth relaxes.

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should pass between the first and second premolars. For mandibular exposures the tube head will be pointed up for negative (-) angulation.

Expose

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MANDIBULAR MOLARS

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MANDIBULAR MOLARS Center the receptor on the molars as close as possible to the lingual surfaces of the teeth.

Align the anterior border of the receptor with the second premolar so that the image captured on the anterior edge of the receptor will be the distal third of the second premolar. Position the biteblock on the occlusal surface of the teeth to be radiographed.

A cotton roll may be inserted between the maxillary molars and the biteblock for patient comfort. Ask the patient to slowly, but firmly bite onto the block to maintain the correct position. The receptor should be straightened as the patient closes and the floor of the mouth relaxes.

Align the central ray perpendicular to the bisector vertically and at the desired interproximal contact to be viewed. Horizontally, the central ray should pass between the contact of the first and second molar. For mandibular exposures the tube head will be pointed up for negative (-) angulation.

Expose

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THE BITEWING FILM

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BITEWINGS

Bitewing radiographic images are usually exposed with an indicated vertical angulation of +10 degrees (tube head points down for positive (+) angulation). This angulation provides an acceptable compromise for the differences between the long axis inclinations of the maxillary and mandibular teeth. Horizontal angulation is aligned with the direction of the contact, and the central ray is directed between the contacts of the teeth to be radiographed.

The interproximal examination may be done using a special type 3 bitewing receptor but is preferably achieved by using four type 2 receptors fitted with a tab. There are also receptor holding devices available that support the receptor as well as provide an external reference for positioning the tube head. The patient stabilizes the receptor by gently biting together on the manufactured tab or on the holding device.

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MAXILLARY OCCLUSAL

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MAXILLARY OCCLUSAL

Uses: To view the maxilla for anterior alveolar fractures, cysts, supernumerary teeth and impacted canines, and to view pathology at the apices of the incisors. It is not used to diagnose periodontal conditions.

Patient positioning: The patient is seated with the sagittal plane perpendicular to the floor and the occlusal plane parallel to the floor. Before any radiographic images are exposed, the patient must be draped with a protective apron and thyroid collar. The apron must be properly placed to avoid interference with the radiographic exposure.

Receptor placement: Use a type 4 receptor. With the tube side of the receptor toward the maxilla, the receptor is placed crosswise in the mouth, like a cracker. It is gently pushed backwards until it contacts the anterior border of the mandibular ramus. The patient bites down gently to maintain position.

Exposure factors: Follow the recommendations of the receptor and equipment manufacturer.

Direction of the central ray: The central ray is directed at the center of the receptor with a vertical angulation of +65 degrees and a horizontal angulation of 0 degrees. In this case, the central ray will pass through the bridge of the nose

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MANDIBULAR OCCLUSAL

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MANDIBULAR OCCLUSAL

Uses: To view the anterior portion of the mandible for fractures, cysts, root tips, and periapical pathology. It provides a very good view of the symphysis region of the mandible

Patient positioning: The patient is seated with the head tilting slightly backward, so that the occlusal plane (ala-tragus line) is 45 degrees above the horizontal plane. Before any radiographs are exposed, the patient must be draped with a protective apron and thyroid collar. The apron must be properly placed to avoid interference with the radiographic exposure.

Receptor placement: Use a type 4 receptor. With the tube side of the receptor toward the mandible, the receptor is placed crosswise in the mouth, like a cracker. It is gently pushed backwards until it contacts the anterior border of the mandibular ramus. The patient bites down gently to maintain position.

Exposure factors: Follow the recommendations of the receptor and equipment manufacturer.

Direction of the central ray: The central ray is directed between the apices of the mandibular central incisors and the tube is angled at -55 degrees relative to the receptor plane

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INFECTION CONTROL

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FIRST THINGS FIRST – INFECTION CONTROL!

There are many opportunities for cross contamination in both digital and film-based radiography for semicritical and noncritical items.

First of all, it should be understood that the standard protocols such as hand hygiene, gloves, attire, barriers, and personal protective equipment must be observed. Extraoral devices are considered noncritical, meaning they do not come in contact with the mucous membranes but still require observation of aseptic technique. Examples include the lead apron, cone, tube head (PID), exposure button, control panel, computer keyboard/mouse, at-risk countertops, or other surfaces that have potential for risk of cross contamination.

According to the ADA Council on Scientific Affairs, "All extraoral devices that will be contacted during the procedure should be either disinfected between patients or protected by a barrier and changed between patients. An EPA-registered hospital-level disinfectant with low-to-intermediate activity should be used to treat any surfaces that become contaminated."

Film and processing protocols deserve discussion since they are prime areas for cross contamination. Joen Iannucci and Laura Howerton suggest the following steps for film handling:

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FILM HANDLING DURING PROCESSING WITH BARRIERS

Place disposable towel on work surface in darkroom/processor

Place container with contaminated films next to towel

Put on gloves

Take one contaminated film out of container

Tear open barrier envelope

Allow film to drop on paper towel

Do not touch film with gloved hands

Dispose of barrier envelope

After all barrier envelopes have been opened, dispose of container

Remove gloves and wash hands (film packets are still unopened; only the barriers have been removed)

Unwrap and process films (in daylight loader or darkroom)

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LABEL A FILM MOUNT, PAPER CUP, OR ENVELOPE AND USE TO COLLECT PROCESSED FILMS WITHOUT BARRIER ENVELOPES

Label a film mount, paper cup, or envelope and use to collect processed films without barrier envelopes

Place disposable towel on work surface in darkroom/processor

Place container with contaminated films next to towel

Put on gloves

Turn out darkroom lights if in darkroom

Take one contaminated film out of container

Open film packet and slide out lead foil backing and black paper; discard film packet wrapping

Rotate foil away from black paper and discard

Without touching film, open the black paper wrapping

Allow film to drop on paper towel

Do not touch film with contaminated gloved hands

Discard black paper wrapping

After all packets have been opened, remove gloves carefully and place gloves in contaminated holder

Wash hands

Process films

Label a film mount, paper cup, or envelope and use to collect processed films

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ALTERNATIVE METHOD FOR DAYLIGHT LOADERS AND FILMS WITH PLASTIC (NON PAPER) OUTER COVERING

Soak films in an EPA moderate-level chemical germicide for the recommended time

Put on clean gloves

Rinse film packets with water

Place on barriered surface and dry with paper towels

Remove gloves, wash hands, don new gloves

Process films

Label a film mount, paper cup, or envelope and use to collect processed films

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GUIDELINES

Gone are the days of cookie-cutter bitewings every six months and full mouth series every five years for all patients. FDA and ADA recommend use of exposure guidelines that take into account patient dental and medical history; even clinical exams are part of these guidelines. This means that each patient is individually assessed for the need for radiographs.

For example, bitewings for recalls at six- to 12-month intervals are not recommended on a routine basis unless they are accompanied by the appropriate risk factors delineated in the guidelines. Such risk factors include a patient with recent caries experience, numerous restorations, and poor oral hygiene.

According to the FDA, the guidelines entitled "The Selection of Patients for X-ray Examination" were developed in 1987 by a panel of dental experts convened by the Center for Devices and Radiological Health of the U.S. Food and Drug Administration (FDA).

These guidelines stemmed from a concern about the public's exposure to radiation. From this the guidelines specific for dental X-rays were developed, and these were in place for 15 years. Revisions in 2002/2004 took into account advancing technology. Some of the updates include:

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UPDATES

An additional "other circumstances" category, including implants and remineralization of enamel

Restorative, endodontic needs, and other pathology

Inclusion of edentulous patients

Use of panoramics

Clarification that bitewings can be either horizontal or vertical

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GUIDELINES

The guidelines categorize 1) new and recall patients, 2) age and dental development stage from children with primary through adults with edentulous dentition, and 3) risk category based on presence or absence of certain conditions. These guidelines must be used in conjunction with a complete medical/dental history and clinical exam.

Some examples of applying these guidelines include:

1. An adult recall patient with no caries risk and no clinical caries during the exam should have bitewings every 24 to 36 months.

2. A child with the same situation is recommended for bitewings every 12 to 24 months if the proximal surfaces cannot be visually examined.

(Note that these examples are low risk, no clinical caries categories.)

3. An adult recall patient with caries or increased risk for caries should have bitewings every six to 18 months.

4. A child in the same situation is recommended for bitewings every six to 12 months if proximal surfaces cannot be visually examined.

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IT DEPENDS

Ultimately, the guidelines defer to the clinician's judgment and an individual evaluation of each case. In some instances, an individual case and accompanying clinical judgment will merit six-month intervals on bitewings, while others will only need bitewings every 12, 18, 24, or 36 months.

Guidelines are available at the FDA's Web site at www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm116506.htm.

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ALARA

Every dental professional should be aware of the "As Low as Reasonably Achievable" (ALARA) Principle, in which consumer diagnostic radiation exposure is minimized. There are many methods to accomplish this. Examples of good radiologic practice include: Use of digital radiography (exposure times are reduced by 50% to 80% from conventional high-

speed film)

Patient selection criteria, including health history and oral exam prior to taking radiographs

Collimation of the beam to the size of the receptor whenever feasible

Proper film exposure and processing techniques to avoid retakes

Use of leaded aprons and thyroid collars with both film and filmless images

Other techniques and safety protocols that protect patients from unnecessary secondary radiation.

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LEAD APRONS AND COLLARS

According to the FDA, "The amount of scattered radiation striking the patient's abdomen during a properly conducted radiographic examination is negligible. However, there is some evidence that radiation exposure to the thyroid during pregnancy is associated with low birth weight. Protective thyroid collars substantially reduce radiation exposure to the thyroid during dental radiographic procedures. Because every precaution should be taken to minimize radiation exposure, protective thyroid collars and aprons should be used whenever possible. This practice is strongly recommended for children, women of child bearing age, and pregnant women."

Unlike the early days of primitive equipment with minimal safeguards and long exposures, today's radiographs afford the patient the least possible exposure with the best diagnostic information. From the times of Roentgen, Kells, and Rollins, the contrast with today's technology and safe practices is remarkable.

Ellen Standley, RDH, BS, MA, is president of CDHA and a long-time active member of ADHA, CDHA, and the Sacramento Valley Dental Hygienists' Association. She is a professor of Dental Hygiene at Sacramento City College and holds memberships in the California Dental Hygiene Educators' Association and the American Academy of Dental Hygiene. Ms. Standley can be reached at [email protected].

Heidi Emmerling, RDH, PhD, is interim director and assistant professor of dental hygiene at Sacramento City College and a CODA site consultant. She is owner of Writing Cures, a writing and editing service, and co-author, of The Purple Guide: Paper Persona, a guide to preparing professional development and job search materials. Dr. Emmerling can be reached at [email protected].

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HARP ACT

The Healing Arts Radiation Protection (HARP) Act , and the X-ray Safety Code (Regulation 543) cover the use of x-rays for the irradiation of human beings in the province of Ontario. These regulations govern radiographic equipment, their operation, and the qualifications of individuals operating them. Section 5(2) of the HARP Act lists members of the College of Dental Hygienists of Ontario (CDHO) as persons deemed to meet the qualifications prescribed by the regulations. This means that even though dental hygienists complete radiography training in a dental hygiene program, they are not considered HARP certified until they are registered with the CDHO. The HARP Act does not approve or certify dental hygiene radiography programs. Only the CDHO has the authority to grant HARP certification to dental hygienists in Ontario.

Dental hygienists who currently hold a general or specialty certificate of registration are deemed to be HARP certified. Those who have resigned, are suspended or revoked from the College are not considered HARP certified. The Act also states that an inspector may enter and inspect the premises and require the production of proof that any person who operates an x-ray machine meets the qualifications and requirements. A ministry inspector will accept a dental hygienist’s certificate of registration (or CDHO wallet card) as proof that they meet the requirements.

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DIGITAL

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DIGITAL IMAGE

Digital radiography is technology that uses a sensor, computer and monitor to acquire, process, store, retrieve and display the radiographic image. In some cases, a scanner is required. Unlike a conventional radiograph, a digital radiographic image has no physical form. The dental radiograph seen in film-based radiography is analogous to a painting, where colors blend continuously to create the finished canvas. In filmless digital radiography, the image is more like a mosaic, tiny pieces put together to make the final portrait. These tiny dots of information, called pixels, are short for “picture elements.” The more pixels that are present, the higher the resolution, greater the sharpness and an overall better quality image is produced.

Each pixel is assigned a number in the computer from 0 to 255, each representing a specific shade of gray, from pure black at 0 to pure white at 255. This gray scale displayed by the monitor is another important characteristic of a digital image because it is critical in our ability to diagnosis or interpret oral conditions. Despite the 256 shades of gray available, the human eye can only detect 32-shade levels unaided5.

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CONTINUED

Most digital systems use a conventional dental x-ray unit as the source for x-radiation. With digital radiography, we “acquire” an image rather than “take” a radiograph like in film-based radiography. Digital radiography requires 50 percent to 80 percent less radiation exposure in order to achieve an image, depending on the speed of film currently being used in the practice6. Besides the required computer and monitor, basic components of digital systems include imaging software, image-recording device and scanner if needed.

Many systems are available today and include intraoral, panoramic and cephalometric systems.

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TYPES

Direct: This is the fastest method to acquire an image and requires a specially coated electronic receptor, called a sensor, which records the

image. The sensor is placed in the oral cavity in a similar manner as you would place a film packet. When exposed to x-radiation, the sensor converts the x-rays to an electronic form that is read by the computer almost immediately. Intraoral sensors are comparable in size to an intraoral film packet and may be wired or wireless. Wired sensors are connected to the computer via a fiberoptic cable and wireless sensors communicate with the computer via a radio frequency. (Currently only Schick Technologies sells a wireless sensor.)

Indirect: This is the slowest method and requires a conventional dental radiograph. The film-based radiograph is converted into a digital image

using a x-ray film scanner with a transparency adapter option and transferred to a computer for display and storage. A digital still or video camera can also be used to take a photograph of the dental radiograph. The resulting image is considered a copy of the original.

Semi-indirect: This method requires a special sensor called a photostimuable phosphor plate (PSP) and a special scanner. The sensor is coated on one

side with reusable phosphorus that stores the x-radiation until a scanning device converts it into a digital image. The PSP plate looks and handles like dental film, and the image is acquired when exposed to x-rays. Step two involves placing the plate in a special scanner, specific to the imaging software, to convert it to a digital image. This method is not as fast as the direct method, but quicker than the indirect method. The image stored on the plate is erased by exposing it to bright light. Once the plate is cleared, it can be used again. Some systems offer a scanner that also clears the plate, while other systems require the plate to be placed separately in bright light.

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TECHNIQUE

The paralleling technique is the preferred method of exposure. Sensor holding devices are available to assist the clinician in stabilizing the sensor in the mouth and acquiring a diagnostic image. A poorly placed sensor or PSP plate results in a poor image. New disposable holding devices are also available.

Digital sensor aids are available to ease patient comfort and prevent sensor slippage as well as add a barrier cover to the wired sensor. A finger cot can also be used to cover a sensor if the patient is not allergic to latex. These adhesive sponge pads can also be attached to the PSP envelope to add rigidity and help protect it from damage during exposure.

Despite less x-radiation exposure, lead or lead-free aprons are still needed to protect patients, this includes thyroid shields for intraoral exposures.

Continue to follow the FDA/ADA guidelines for prescribing dental radiographs.

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SENSORS

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STEPS FOR THE SENSOR TECHNIQUE

Steps: ProcedureStep 1 Create a patient file and template for images.Step 2 Prepare and cover receptor, then place in holder instrument.Step 3 Pre-set the exposure time.Step 4 Place radiation shield on patient and explain procedure.Step 5 Place covered receptor in mouth in the proper position.Step 6 Align vertical & horizontal angle and center x-ray beam.Step 7 Prepare software for exposure, move behind barrier and trigger exposure.Step 8 Remove receptor; view direct image on monitor or scan plate.Step 9 Evaluate result; retake, enhance and/or save as needed.

Step 10 Or acquire additional images as needed, repeat steps 8 and 9 as appropriate.

Adapted from: Williamson GF. Digital radiography in dentistry. J Prac Hyg, Montage Media Corporation, November-December, 2004;13.

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YOUR IMAGES ARE NOW IN THE COMPUTER!

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PHOSPHOR PLATES

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REFERENCES

http://www.rdhmag.com/articles/print/volume-31/issue-1/features/dental-radiography.html

1. Wenzel A. Two decades of computerized information technologies in dental radiography. J Dent

Res 2002; 81(9):590-3.

2. Dental Products Report (DPR). Radiography: A DPR survey report. Dental Products Report. 2005 May;

Accessed on July 23, 2007.

3. Russo JM, Russo JA, Guelmann M. Digital radiography: a survey of pediatric dentists. J Dent Child

(Chic). 2006 Sep-Dec;73(3):132-5.

4. Marrow, SG. Digital radiography: examining the choices. Loma Linda University Dentistry.

Winter/Spring 2006;17(1):12.

5. Bushong SC. Radiologic science for technologists: physics, biology and protection. 7th edition. St

Louis, MO: CV Mosby., 2001, 374.

6. Haring J, Howarten L. Dental Radiography Principles and Techniques. 3rd ed. Philadelphia, PA:

Elsevier; 2006, 351-2.

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