Xray - Outcome 6

Question 1

How much does digital imaging reduce radiation exposure?

Answer 1

Digital imaging reduces radiation exposure from 50 to 80%

Question 2

The advantages of digital radiography are..

Answer 2

Instant image

Decrease in time for processing

Improved grayscale through image enhancement

Reduced radiation

Capability for electronic transmission

Patient education

No need for processing chemicals

Question 3

The disadvantages of digital radiography are..

Answer 3

Overhead

Debate over the quality of an image

Infection control (unable to sterilize sensor)

Bulkiness of the sensor (patient comfort)

Concerns about legal implications as the original can be modified.

Question 4

Basic Principles of Shadow Casting

Answer 4

1. Xrays should be emitted from the smallest source (target or focal spot) possible - To produce an image with sharp detail, we need an X-ray beam with parallel rays. The smaller the point at which X-rays are generated, the more parallel the rays will be (smaller focal spot - better detail)
2. The distance from the Xray sourace (focal spot or target) to the object should be as long as possible - The added distance results in an image with less magnification and a sharper outline
3. The distance between the object (oral structure) and the film should be as short as possible. - Placing the film as close to the object as possible decreases distortion by reducing magnification
4. The film and the long axis of the object should be parallel. - A film not parallel to the long axis of the tooth will display magnification and distortion
5. The x-ray should be directed perpendicular to the film - If the x-ray beam is not perpendicular, the image will be distorted on the film, and will not be representative of the object being examined (shorter or stretched out)

Question 5

Interproximal / Bitewing Radiographs

Answer 5

Interproximal radiographs show the crowns of the teeth and alveolar crests of both the maxillary and mandibular arches on the same film

Question 6

Greatest value of the bitewing radiograph?

Answer 6

One of the greatest values of the interproximal radiograph is that it reveals caries in the earliest stages that are not clinically evident. It also reveals changes in the pulp, overhanging restorations, improperly fitted crowns, recurrent decay beneath restorations, and to some degree, loss of alveolar bone

Question 7

Periapical radiographs are required to assess…

Answer 7

Periapical radiographs are required to assess the entire tooth, the crown, the root, and its surrounding tissues.

Question 8

What are the two basic techniques employed in intra-oral radiography?

Answer 8

the bisecting angle and the paralleling

Question 9

Other names for the paralleling technique?

Answer 9

Right angle or long cone

Question 10

Positioning for Paralleling technique

Answer 10

Film is placed parallel to the long axis of the tooth. The film must be positioned away from the lingual surface of the tooth in most areas. Paralleling is achieved by placing the film as parallel as possible to the long axis of the tooth while taking into consideration the anatomical features. The central ray is then directed so it is perpendicular to the long axis of the tooth being exposed.

Question 11

Difficulty with the paralleling technique?

Answer 11

The difficulty with the paralleling technique is film placement with a shallow roof of the mouth creating discomfort.

Question 12

Successful use of the paralleling technique depends on maintaining certain conditions:

Answer 12

1. The film plane must be flat and positioned so that it covers the necessary teeth.
2. The film must be parallel to the long axis of the teeth.
3. In all areas, except the mandibular molars, the film must be positioned away from the lingual surface of the teeth and located in the deeper areas of the mouth to cover the apices of the teeth.
4. The face of the open cone must be kept parallel to the film plane by adjusting both the vertical and horizontal angulations. In this way, the central ray is directed perpendicularly to the film plane.
5. The cone must be directed so that all of the film is covered by the x-ray beam.

Question 13

What is a film holder?

Answer 13

A film holder is a device that holds a dental X-ray film far enough away from the teeth and surrounding tissues to keep it parallel with the teeth being exposed. Many film holders have an external marker, usually called a “locator ring,” to help the operator position the PID exactly over the film

Question 14

A number of film holders are available for exposing radiographs using the paralleling technique

Answer 14

-Rinn XCP (Extension Cone Paralleling) film holders are the type of film holders that we use at SAIT.
-Stabe styrofoam bite blocks and snap-a-ray film holders are also commonly used.

Question 15

Tips for placement of a film holder in a patient’s mouth

Answer 15

Always soften the corners of the film that contact soft tissue: this contributes greatly to patient comfort.

When exposing the maxillary anterior teeth, place the film deep in the mouth: this allows the film to parallel the teeth as much as possible. The patient will bite on the end of the bite-block. Make two-point contact before asking the patient to close on the bite-block.

When exposing the maxillary posterior teeth, place the bite-block in the mouth so that the upper edge of the film is at the highest part of the palate. Angle the bite-block up to the occlusal surfaces of the teeth. Hold in position and ask the patient to close on the bite- block.

When placing the film for the lower anterior teeth, compress the tongue back in the mouth with the bite-block while placing the film in position. (Having the patient close his mouth in a protrusive manner may aid you in this procedure). Make two-point contact before asking the patient to close on the bite-block.

When placing the film for the lower posterior teeth, the film may be placed close to the lingual surfaces and still be parallel to the long axis of the teeth. Insert indicator in the inside holes of plastic bite-block.

To ensure patient comfort and stability of the XCP instrument, a cotton roll on the opposing arch should be used. Use orthodontic elastics to secure cotton roll to plastic bite block.

There may be instances in which your patient will have missing teeth. The bite-block may take an uneven position in the mouth when the patient closes. To maintain an even plane, use a cotton roll to replace the missing teeth.

Question 16

Which way are films/receptors typically placed for anterior teeth?

Answer 16

Vertical

Question 17

Which way is the film/receptor typically placed for posterior teeth?

Answer 17

Horizontal

Question 18

The advantages of the X-Tension Cone Paralleling (XCP) technique are:

Answer 18

Simplicity - Eliminates the need for predetermined angulation and positioning of the patient’s head.

Adaptability - Can be used in most offices regardless of space limitations, by rotating the chair and/or the patient’s head.

Reliability - Anatomic accuracy of tooth size, length of canals, etc., is assured.

Results - Radiographs that reproduce anatomic structures in their normal size and relationship, free of distortion with minimal superimposition of the zygomatic shadow, and exhibiting maximum detail definition.

Question 19

“TPR” Method stands for?

Answer 19

Tilt-position-relax method

Tilt - For maxillary exposures, tilt the film holder as you place it into the patient’s mouth, trying not to touch any tissues until the film is in its proper position. The same procedure is used for mandibular exposures except for the posterior teeth when the cheek and tongue must be contacted during film placement.

Position - With the film still tilted, carefully position it exactly in line with the teeth you wish to radiograph, remembering that the central ray must be directed through the teeth to the center of the film.

Relax - As the patient begins to close on the bite-block, relax your grip on the bite-block handle. This will allow the film to move itself into the best possible placement for each patient. The patient must close firmly or the periapical areas of the teeth will not be adequately recorded on the resultant radiograph.

Question 20

Interproximal films can be made using:

Answer 20

XCP Bite-wing instrument
Cardboard tabs (loops)

Question 21

Bitewings

Answer 21

The bite-wing survey (BWS) can be made with two to eight films using the appropriate size film. Exposures can be made in both the anterior and posterior regions of the mouth; however, anterior exposures are rarely made because it is easier to detect caries in the anterior teeth through visual examination and transillumination. Over 95% of all interproximal exposures are made in the posterior regions. Interproximal films can be made with the film in either a vertical or horizontal orientation. The horizontal placement is the most common but vertical placement is increasing in popularity.

Question 22

What size of film is recommended for adult bitewings?

Answer 22

For most adults, two #2 size films for bite-wings films on each side are recommended because the curve of the arch may require two different horizontal angulations when moving from the bicuspid to the molar region.

Question 23

Bitewing sizes for children

Answer 23

One posterior bite-wing on each side is usually all that is needed for children under twelve or an adult with a small jaw. For a child, two #0-size films for bite-wing films on each side are used

Question 24

Correct horizontal angulation for a bite-wing radiograph is crucial because…

Answer 24

Correct horizontal angulation for a bite-wing radiograph is crucial to the diagnostic value of the film. Even a slight amount of overlap may lead to a misdiagnosis. The goal is to obtain bite-wings with no overlapping of the interproximal contacts.

Question 25

Overlapping of contact areas for bitewings

Answer 25

Since the primary purpose of a bite-wing is to obtain a clear view of the contact areas and interproximal spaces, overlapping on a bite-wing is a critical error. Overlapping of contact areas are generally caused due to a technical error such as incorrect horizontal angulation. Overlapped areas on periapical films are technical errors as well but are not as serious because the purpose of a periapical (PA) film is to view the “periapical area” not the interproximal aspect

Question 26

The Bisecting Angle Technique of Exposing Peri-Apical Radiographs

Answer 26

The Bisecting Angle technique is another method that can be used to expose peri-apical films. The Bisecting Angle technique for the radiographic exposure of peri-apical films is a technique whereby the central ray (CR) of the x-ray beam is directed at right angles to an imaginary line which bisects the angle formed by the long axis of the tooth or teeth being examined and the plane in which the film is positioned behind the tooth or teeth

Question 27

Steps for using the bisecting angle technique

Answer 27

The patient must be positioned with the occlusal plane of the arch being examined parallel to the floor and the mid-sagittal plane perpendicular to the floor.
The film must be placed against the lingual surface of the tooth being examined (film is not parallel to the tooth).
An angle is formed where the film contacts the tooth.
The operator must visualize a line that divides in half, or bisects, the angle formed by the film and the tooth.
The operator must then direct the central ray of the x-ray beam perpendicular to the imaginary bisector.
Then, the central ray must be directed between the contacts of the teeth.
Finally, the film must be centered in the circle of radiation.

Question 28

Direction of the Central Ray

Answer 28

If we direct the CR at a right angle to the film, the resulting image will be shorter than the actual structure. If we direct the CR at a right angle to the long axis of the tooth, the resulting image will be much longer than the actual structure. Even when used accurately, this method produces a greater magnification of the structure being examined, than the paralleling technique

Question 29

Disadvantages of the bisecting angle technique

Answer 29

The operator cannot see the angle formed by the tooth and film.

The operator must imagine the line that bisects the angle.

The operator cannot see exactly where the film is, and therefore may have difficulty centring the film in the circle of radiation.

The Bisecting Angle technique requires more perseverance on the part of the novice operator to develop skills in the judgment of the angulations necessary for the reproduction of accurate images.

Question 30

Examples of commercially available intra-oral film holders that can be used with the bisecting angle technique include:

Answer 30

1. RINN Bisecting Angle Instrument (BAI)
   These instruments, similar to the RINN XCP film holders (bite blocks, aiming rings, and indicator arms), have been designed to assist in determining vertical and horizontal angulations and prevent cone-cutting.
2. Stabe Bite-Block
   For use with the BA technique, the scored section is removed and the film is placed as close to the teeth as possible.
3. Eezee-Grip (Snap-A-Ray)
   Place the “dot edge” of a size two film into the teeth of the holder and secure the film with the sliding lock. The front of the film should face the wide part of the holder. Place the “dot edge” of a size two film into the teeth of the holder and secure the film with the sliding lock. The front of the film should face the wide part of the holder.

Question 31

Produce an occlusal radiograph for maxillary teeth

Answer 31

For an adult, a size #4 film and a child size #2 film are recommended.

Adjust the headrest so that the patient’s head is upright and the maxillary arch parallel to the floor, and place a lead apron.

Set the control panel to bring the extension arm in close to the patient.

Place the film with the tube side towards the area being radiographed (maxilla) with the orientation allowing for maximum anatomical coverage. Ask the patient to gently occlude.

Confirm the ID dot is placed anteriorly and the film is centered.

Bisect the angle between the teeth and the film.

Center the tubehead (+65 degrees) over the film with the CR perpendicular to the bisected angle.

Confirm patient is still, and expose the film.

Question 32

Produce an occlusal radiograph for mandibular teeth

Answer 32

For an adult, a size #4 film and for a child, a size #2 film is recommended.

Slightly recline the patient and place the lead apron.

Set the control panel and bring the extension arm in close to the patient.

Place film with the tube side towards the area being radiographed (mandible) with the orientation allowing form maximum anatomical coverage. Ask the patient to gently occlude.

Confirm the ID dot is placed anteriorly and the film is centered.

Bisect the angle between the teeth and the film.

Center the tubehead (90 degree angle to the film) with the CR perpendicular to the bisected angle.

Confirm patient is still, exposed the film.

Question 33

The following guidelines will minimize film-positioning errors

Answer 33

-The distal surface of the cuspid should be visible in any bicuspid view.

-The third molar region should be visible in the molar view.

-When exposing a specific tooth, e.g. 2.6, the tooth/teeth of interest should be centered.

Question 34

Errors in Exposing: Eleongation

Answer 34

This is one of the most frequent errors made by beginners. Paralleling the open face of the cone (PID) with the film will ensure the correct vertical angulation. When the image of the tooth is longer than the tooth itself, it is called elongation. This is caused by insufficient vertical angulation (too shallow) of the tube head.

Question 35

Errors in Exposing: Foreshortening

Answer 35

This is the opposite of elongation. The image of the tooth is shorter than the actual tooth. This is caused by too much (too steep) vertical angulation. If a vertical angulation of +45 degrees is necessary and the angulation is set at +55 degrees, foreshortening occurs.

Question 36

Errors in Exposing: Horizontal Overlap

Answer 36

Improper selection of the horizontal angulation will result in overlapping of interproximal contact areas. This occurs when the central rays are not directed through the contact points parallel to the interproximal surfaces causing super-imposition of the proximal surfaces of adjacent teeth.

Question 37

Errors in Exposing: Cone Cutting

Answer 37

This is caused by failure of the central ray to expose the entire film. The film will have a crescent-shaped clear area. This happens when the x-ray beam is not directed at the centre of the film. The primary beam must encircle the film.

Question 38

Errors in exposing: Film bending

Answer 38

Sometimes, it is appropriate to gently curve or bend the film, allowing the film to follow the contours of the oral anatomy more readily. Gross bending or creasing causes image distortion. The distortion caused by film bending is localized to the “bent” region. Excessive bending of the film is most frequently found in exposures of the cuspid area. The portion of the film which was bent will have an image similar to an elongated image. However, only the roots of the tooth appear distorted while the crowns remain relatively true in dimension. The cause of excessive bending is usually improper film positioning. The film must be placed deep in the mouth for all exposures except mandibular posteriors. If you bend or crease the film, it will have black lines on it when processed.

Question 39

Errors in exposing: Reversed film

Answer 39

The sensitive side of the film must face the x-ray tube. When the film is exposed with the wrong side facing the tube, the x-rays must pass through the lead foil backing. This prohibits some x-rays from reaching the film. The resulting images lack density: The overall appearance is lighter and weaker than normal; a peculiar pattern known as the “herringbone pattern” appears on the radiograph. This is due to the embossed pattern on the lead foil backing. The images on this film are reversed in relation to the dot.

Question 40

Errors in exposing: Improper film selection

Answer 40

Incorrect selection of film size will cause many problems. If the film selected is too small, the tooth of interest may be missing. If the film selected is too large, the patient may not accept the film comfortably, which can result in areas of distortion, missed apical areas, patient movement, or overlapping of structures. The correct size film is that which will cover the area of interest and be comfortable for the patient.

Question 41

Errors in exposing: Double exposure

Answer 41

A double exposure results when an already exposed film is placed back into the mouth and re-exposed. Because the film was exposed twice, it has an overall appearance of being too dark as well as a double image. You must be very careful to separate exposed and unexposed films. Double exposure of films can be avoided by paying attention to detail and using a systematic approach to placement and exposure.

Question 42

Errors in exposing: Double Image/Double Exposure

Answer 42

A double image is caused when the film is moved slightly during the exposure and then held firmly in the new position during the remainder of the exposure. The image is “doubled” or has a shadowy appearance. Instruct the patient to hold the film securely in the exact position you have placed it.

Question 43

Errors in exposure: Saliva Leak

Answer 43

If the film is bent too sharply or left in the patient’s mouth too long, the seal around the edge of the packet may break. This allows saliva to leak into the film. When it contacts the film emulsion it causes the surrounding black envelope to adhere to the film. Later, when the film is stripped, the black paper remains stuck to the film in these areas.

Question 44

Errors in exposing: Blurred image

Answer 44

A blurred image is usually caused by the movement of the patient’s head, film, or PID/tubehead during the exposure. Remember, caution the patient to “sit still” while the exposure is being made.

Question 45

Errors in exposure: Incorrect instrument assembly

Answer 45

When assembling film holders, always look through the locator ring to make sure that the film is centered in the ring. If it is not, reassemble the film-holding instrument.

Question 46

Errors in exposure: Overexposure (dark image) / Underexposure (light image)

Answer 46

One can overexpose a film by incorrect selection of (1) exposure time (too long), (2) kvp, and (3) mA. Since most machines have a fixed kvp and ma, overexposure is usually caused by improper time (tooth) selection. An overexposed film will appear too dark. If you select too short of an exposure time, the finished radiograph will appear too light (underexposed).

Question 47

Errors in exposure: blank film/no image

Answer 47

A blank film usually results when no x-rays are generated in the tube during what you thought was the exposure time. Make sure the unit is plugged in securely and that it is functioning properly. A partial image can result from the lead apron in the path of the x-ray beam. Always make sure the thyroid collar of the lead apron is securely fastened around the patient’s neck.

Question 48

Errors in exposure: Superimposed images

Answer 48

Failure to remove an appliance from the patient’s mouth before exposing a film will result in the superimposition of these structures over the areas exposed.

Question 49

Patient Positioning for Panoramic

Answer 49

Matching the plane-in-focus and the focal trough to the patient’s anatomy will correct many of the errors. If the roots of the anterior teeth are centered in the focal trough, the neck is straight and the occlusal plane is tilted slightly down:

Hard palate shadow is minimized

Equal detail and uniform length of upper and lower anterior roots is achieved

Minimal spinal shadow is present

Question 50

Panoramic Errors: Metal Objects

Answer 50

If METAL OBJECTS are not removed from the patient’s head and neck area, they will appear on the resulting films, obscuring diagnosis; e.g., earrings will obscure the molar regions and a bib chain will obscure the lower anterior

The lead apron (vest type) must be placed carefully so it does not cause large unexposed areas on the film.

Question 51

Panoramic Errors: Occlusal Plane Too Low

Answer 51

If the occlusal plane is positioned TOO LOW, the roots of the lower anterior will be placed out of the focal trough. They will appear foreshortened and blurred. The palate will form an occlusal plane “smile” and the condyles will tilt inwards

Question 52

Panoramic Errors: Occlusal Plane Too High

Answer 52

If the occlusal plane is positioned TOO HIGH, the upper anterior roots are placed out of the focal trough and will appear blurred and foreshortened (Robinson, 2024). The hard palate will form an occlusal plane “frown” superimposed over the maxillary roots, and the condyles tilt outwards

Question 53

Panoramic Errors: Slumped Posture

Answer 53

if the patient is positioned in a “slumped” posture, the spinal cord will be superimposed over the anterior area of the mouth (Robinson, 2024). The anterior region will appear extremely light and there will be loss of detail because of the superimposed shadow of the spine. Patients with very heavy bone and neck structure may present spinal shadow even though positioned properly. It may be necessary to increase the kvp 5-10 to compensate for this

Question 54

Panoramic Errors: Mid-Sagittal Plane not vertical

Answer 54

If the patient is not positioned with the mid-sagittal plane vertically, there will be unequal left-right magnification. The bite guide and holder will be off-center also. If the bite guide is not used, the upper and lower anterior crowns will appear overlapped and blurred. If the patient’s chin is not on the chin rest, the lower border of the mandible will be located too high within the film

Question 55

Dr. Sait suggested that you take periapicals and bitewings. What is the difference and do
I need to have both types taken?

Answer 55

 Periapical is a specific xray that show the entire tooth (root tip-crown) &
supporting structures.
 Bitewings – show max and mand crowns and bone level and are primarily used
to detect cavities in between the teeth and to assess bone levels.
 Both types are required for the exam today because the DDS will use both types
for an accurate diagnosis.
 PA’s are typically used for specific concerns (cold sensitvity, swelling, pain etc..)
 BW’s are used for an overall exam of all quads to look for decay that cannot be
seen in between the teeth.

Question 56

What are the characteristics of a diagnostically acceptable periapical?

Answer 56

Contrast, magnification, sharpness, all required anatomy visible

Question 57

Teeth required in bitewings

Answer 57

-Right side posterior – 1.8-1.6 & 4.8-4.6

 Right side premolar – 1.3 (distal) -1.6 (mesial) & 4.3(distal) – 4.6 (mesial)

 Left side posterior – 2.8-2.6 &.3.8-3.6

 Left side premolar – 2.3(distal) – 2.6(mesial) & 3.3(distal)-3.6(mesial)

Question 58

Describe what closed contacts look like
on a BW image and how can this be corrected.

Answer 58

Closed contacts have overlap. No space between teeth and unable to detect
interproximal cavities.
Adjust horizontal angulation to make sure the central ray is directed through the
contacts.