Lecture 6

Question 1

What is a benefit of premolar PA placements when it comes to patient toleration?

Answer 1

Premolar placements are easier for the patient to tolerate.

Question 2

How do premolar PA placements affect the gag reflex?

Answer 2

Premolar placements are less likely to evoke the gag reflex.

Question 3

What should be included in the radiograph for maxillary premolars using the paralleling technique?

Answer 3

All crowns and roots of the first and second premolars and the first molar, including the apices, alveolar crests, contact areas, and surrounding bone. The distal contact of the maxillary canine must also be visible.

Question 4

What should be included in the radiograph for maxillary molars using the paralleling technique?

Answer 4

All crowns and roots of the first, second, and third molars, including the apices, alveolar crests, contact areas, surrounding bone, and the tuberosity region. The distal contact of the maxillary second premolar must also be visible.

Question 5

What should be included in the radiograph for mandibular premolars using the paralleling technique?

Answer 5

All crowns and roots of the first and second premolars and the first molar, including the apices, alveolar crests, contact areas, and surrounding bone. The distal contact of the mandibular canine must also be visible.

Question 6

What should be included in the radiograph for mandibular molars using the paralleling technique?

Answer 6

All crowns and roots of the first, second, and third molars, including the apices, alveolar crests, contact areas, and surrounding bone. The distal contact of the mandibular second premolar must also be visible.

Question 7

How should film or sensors be oriented when using the paralleling technique?

Answer 7

When using film, the white side of the film should face the teeth (“white in sight”), and the identification dot should be placed at the incisal or occlusal edge. When using a sensor, it should be positioned according to the manufacturer’s instructions, with the active side toward the X-ray tube.

Question 8

How are anterior receptors placed in the paralleling technique?

Answer 8

Anterior receptors are always placed vertically to align properly with the anatomy of the anterior teeth.

Question 9

How are posterior receptors placed in the paralleling technique?

Answer 9

Posterior receptors are always placed horizontally to align with the anatomy of the posterior teeth.

Question 10

How should the receptor be positioned in the mouth?

Answer 10

When placing the receptor in the mouth, always lead with the apical end of the receptor and then rotate the beam alignment device into position.

Question 11

Where should the receptor be placed relative to the teeth?

Answer 11

The receptor should be placed away from the teeth and positioned toward the middle of the oral cavity to ensure accurate parallel alignment.

Question 12

How should the receptor be centered during placement?

Answer 12

Always center the receptor over the area to be examined, ensuring alignment with the prescribed placements for proper coverage.

Question 13

What should the patient be instructed to do when positioning the beam alignment device?

Answer 13

The patient should be asked to “slowly close” on the bite block. Ensure that the teeth, and not the lips, stabilize the bite block to prevent distortion of the image.

Question 14

What are the key steps for patient preparation in posterior PA imaging using the paralleling technique?

Answer 14

1. Place Lead Apron and Collar: Protect the patient from radiation exposure.
2. Position the Patient’s Chair: Adjust the chair to the correct height and ensure the patient is upright.
3. Remove Obstructions: Ask the patient to remove eyeglasses, dentures, and retainers to avoid interference.

Question 15

What equipment setup is required before performing a posterior PA using the paralleling technique?

Answer 15

1. XCP Assembly: Assemble the XCP and attach the receptor to ensure the correct side is toward the X-ray beam.
2. Radiograph Machine: Set the exposure device to “ready to expose” and position the tube head closer to the patient. Avoid placing the XCP in the mouth until the software or machine is prepared.

Question 16

How is the XCP positioned inside the mouth for posterior PAs for the paralleling technique?

Answer 16

1. Rotate the XCP with the Receptor: Maneuver the XCP to fit comfortably in the mouth.
2. Push Back the Receptor: Place the receptor as far posteriorly as necessary, focusing on the apical edge of the receptor.
3. Adjust the Bite Block: Ensure the bite block is aligned against the target teeth for stability.

Question 17

How should the PID and machine head be angulated during posterior PA imaging for paralleling technique?

Answer 17

Check alignment from the side, front, and behind the tube head to ensure the central ray is directed properly and covers the receptor area.

Question 18

When is the bisecting technique recommended?

Answer 18

The bisecting technique is used in limited circumstances, such as:
1. Extremely Shallow Palate: When the patient’s anatomy prevents proper receptor placement.
2. Patient Discomfort: If the patient finds it too painful to close on a bite block.
3. Unavailable Paralleling Instruments: When a rubber dam is in use or no XCP is available.

Question 19

How is the bisecting technique similar to the sun-shadow analogy?

Answer 19

• A longer image occurs when the X-ray beam is too flat (like the sun rising).
• A shorter image occurs when the X-ray beam is too steep (like the sun at noon).
• A correct image occurs when the X-ray beam is perpendicular to an imaginary plane that bisects the angle formed by the tooth and receptor, similar to a shadow matching the tree’s height.

Question 20

What are the key steps in performing the bisecting technique?

Answer 20

1. Place the receptor along the lingual surface of the tooth.
2. Ensure the receptor contacts the tooth and forms an angle with the long axis of the tooth.
3. Visualize the imaginary bisector, dividing the angle into two equal parts.
4. Direct the central ray perpendicular to the imaginary bisector to form two congruent triangles.
5. Position the X-ray beam correctly to ensure the tooth’s image matches its actual length.

Question 21

How is the X-ray beam aligned in the paralleling technique?

Answer 21

In the paralleling technique, the X-ray beam is directed perpendicular to the long axis of the tooth and the receptor, ensuring an accurate and distortion-free image.

Question 22

How is the X-ray beam aligned in the bisecting technique?

Answer 22

In the bisecting technique, the X-ray beam is directed perpendicular to the imaginary bisector, which divides the angle formed by the tooth’s long axis and the receptor.

Question 23

How does the length of the tooth appear in the bisecting technique?

Answer 23

The tooth and its image will be equal in length when the X-ray beam is correctly aligned perpendicular to the imaginary bisector, creating two equal triangles.

Question 24

What are the key differences between the paralleling and bisecting techniques?

Answer 24

• Paralleling Technique:
• The receptor is parallel to the long axis of the tooth.
• The X-ray beam is perpendicular to both the receptor and the tooth.
• Produces accurate and distortion-free images.

• Bisecting Technique:
• The receptor is positioned close to the tooth, forming an angle with the tooth’s long axis.
• The X-ray beam is perpendicular to the imaginary bisector.
• More prone to distortion due to angulation errors.

Question 25

When is the bisecting technique advantageous?

Answer 25

• The bisecting technique is useful when the anatomy of the patient (e.g., shallow palate, bony growths, sensitive mandibular premolars) makes the paralleling technique impractical. • It is also an alternative when paralleling instruments are unavailable.

Question 26

What are the disadvantages of the bisecting technique?

Answer 26

• Image Distortion: Errors in vertical angulation can result in elongated or foreshortened images. • Angulation Challenges: It is difficult for the radiographer to accurately visualize the imaginary bisector and determine the correct vertical angulation.

Question 27

Why is the paralleling technique preferred over the bisecting technique?

Answer 27

The paralleling technique is preferred because it produces more accurate and distortion-free images, whereas the bisecting technique is prone to angulation errors and distortion.

Question 28

How does the bisecting technique ensure the image on the receptor is the same length as the tooth?

Answer 28

• The image is equal to the tooth’s length when the central ray is directed at 90 degrees to the imaginary bisector. • The imaginary bisector divides the angle formed by the long axis of the tooth and the receptor into two equal parts. • When the X-ray beam is perpendicular to the bisector, it creates two congruent triangles, ensuring that the length of the tooth and its image match.

Question 29

How does a shallow palate affect the paralleling technique?

Answer 29

A shallow palate can tilt the bite block, affecting the parallelism between the receptor and the long axis of the tooth.

Question 30

What level of parallelism is acceptable for a shallow palate?

Answer 30

A lack of parallelism of up to 20 degrees is acceptable. If the deviation exceeds this, modifications are required.

Question 31

What are the modification options for a shallow palate?

Answer 31

1. Using Cotton Rolls: Place cotton rolls on both sides of the bite block to stabilize the receptor. 2. Increasing Vertical Angulation: Adjust the X-ray beam’s vertical angulation to compensate for the lack of parallelism.

Question 32

What are tori, and how do they impact receptor placement?

Answer 32

• Tori are bony growths in the oral cavity, such as: • Maxillary Tori: Nodular bone along the midline of the hard palate. • Mandibular Tori: Bone growths along the lingual (tongue side) of the mandible. • These can interfere with receptor placement, requiring adjustments.

Question 33

How should receptors be placed for patients with maxillary or mandibular tori?

Answer 33

For maxillary tori, position the receptor behind the torus; for mandibular tori, place the receptor between the tongue and the torus.

Question 34

What is the difference between radiolucent and radiopaque structures in a dental image?

Answer 34

• Radiolucent: Dark or black areas where X-rays pass through soft or thin tissues with little resistance (e.g., dental caries). • Radiopaque: Light or white areas where dense structures resist X-ray passage (e.g., enamel, bone).

Question 35

How does tissue density affect a dental image?

Answer 35

Thin or soft tissues appear radiolucent (dark), while thick or dense tissues appear radiopaque (light).

Question 36

What does the term “periapical” refer to in dental radiography?

Answer 36

• Periapical refers to the area around the apex of a tooth. • For example, a periapical radiolucency could indicate a periapical cyst caused by pulpal necrosis.

Question 37

What is an example of a condition visible in the periapical area?

Answer 37

A periapical cyst, commonly seen secondary to pulpal necrosis, appears as a radiolucent area around the apex of the tooth.

Question 38

What are the types of dental fillings, and how are they categorized?

Answer 38

• Metal Fillings: Examples include amalgam. These are durable but radiopaque. • Non-metal Fillings: Examples include resin composite. These vary in density, appearing slightly radiopaque to radiolucent depending on material properties.

Question 39

How are crowns and bridges classified?

Answer 39

• Tooth-colored Crowns/Bridges: Include materials like ceramic, zirconia, or porcelain, designed to mimic natural teeth. • Non-tooth-colored Crowns/Bridges: Examples include gold, stainless steel, or steel crowns, which are durable and distinctly radiopaque.

Question 40

What other dental materials are commonly used?

Answer 40

• Removable Prosthetics: Such as dentures, designed to replace missing teeth. • Implants: Metal anchors embedded in the jawbone to support crowns or bridges. • Orthodontic Devices: Examples include braces for tooth alignment. • Root Canal Materials: Used to seal and fill tooth canals after treatment.

Question 41

How do metallic and non-metallic restorations appear on a radiograph?

Answer 41

• Metallic Restorations: Absorb X-rays completely, appearing radiopaque (light or white). • Non-metallic Restorations: Vary from radiolucent (dark) to slightly radiopaque, depending on material density.

Question 42

What is the maxillary sinus, and where is it located?

Answer 42

• The maxillary sinus is a paired cavity in the maxilla. • It is located above the maxillary premolar and molar teeth and rarely extends anteriorly beyond the canines.

Question 43

What is the mandibular canal, and what does it contain?

Answer 43

• The mandibular canal is a tubelike passage within the mandible. • It runs from the mandibular foramen to the mental foramen, housing the inferior alveolar nerve and blood vessels.